Podcasts about chloroplasts

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.27.525901v1?rss=1 Authors: Lee, H.-N., V Chacko, J., Gonzalez Solis, A., Chen, K.-E., Barros, J. A. S., Signorelli, S., Havey Millar, A., Vierstra, R. D., Eliceiri, K. W., Otegui, M. S. Abstract: The ubiquitin-binding NBR1 autophagy receptor plays a prominent role in recognizing ubiquitylated protein aggregates for vacuolar degradation during macroautophagy. Here, we show that upon exposing Arabidopsis plants to intense light, NBR1 associates with photodamaged chloroplasts independently of ATG7, a core component of the canonical autophagy machinery. NBR1 coats both the surface and interior of chloroplasts, which is then followed by direct engulfment of the organelles into the central vacuole via a microautophagy-type process. The relocalization of NBR1 into chloroplasts does not require the chloroplast translocon complexes embedded in the envelope but is instead greatly enhanced by removing the self-oligomerization mPB1 domain of NBR1. The delivery of NBR1-decorated chloroplasts into vacuoles depends on the ubiquitin-binding UBA2 domain of NBR1 but is independent of the ubiquitin E3 ligases SP1 and PUB4, known to direct the ubiquitylation of chloroplast surface proteins. Compared to wild type plants, nbr1 mutants have altered levels of a subset of chloroplast proteins and display abnormal chloroplast density and sizes upon high light exposure. We postulate that, as photodamaged chloroplasts lose envelope integrity, cytosolic ligases reach the chloroplast interior to ubiquitylate thylakoid and stroma proteins which are then recognized by NBR1 for autophagic clearance. This study uncovers a new function of NBR1 in the degradation of damaged chloroplasts by microautophagy. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

This week we conclude our two-part discussion with ecologist Mark Ritchie of Syracuse University on how he and his SFI collaborators are starting to rethink the intersections of thermodynamics and biology to better fit our scientific models to the patterns we observe in nature. Most of what we know about the enzymatic processes of plant and animal metabolisms comes from test tube experiments, not studies in the context of a living organism. What changes when we zoom out and think about life's manufacturing and distribution in situ?Starting where we left off in in Episode 62, we tour the implications of Mark's biochemistry research and ask: What can studying the metabolism of cells tell us about economics? How does a better model of photosynthesis change the way we think about climate change and the future of agriculture? Why might a pattern in the failure of plant enzymes help biologists define where to direct the search for life in space?A better theory of the physics of biomolecules — and the networks in which they're embedded — provides a clearer understanding of the limits for all living systems, and how those limits shape effective strategies for navigating our complex world.Welcome to COMPLEXITY, the official podcast of the Santa Fe Institute. I'm your host, Michael Garfield, and every other week we'll bring you with us for far-ranging conversations with our worldwide network of rigorous researchers developing new frameworks to explain the deepest mysteries of the universe.If you value our research and communication efforts, please subscribe, rate, and review this show at Apple Podcasts, and/or consider making a donation at santafe.edu/give. You can find numerous other ways to engage with us at santafe.edu/engage. Thank you for listening!Join our Facebook discussion group to meet like minds and talk about each episode.Follow us on social media:Twitter • YouTube • Facebook • Instagram • LinkedInRelated Reading & Listening:Ritchie Lab at Syracuse University | Mark's Google Scholar Page | Mark's soil ecology startupReaction and diffusion thermodynamics explain optimal temperatures of biochemical reactionsby Mark Ritchie in Scientific ReportsThermodynamics Of Far From Equilibrium Systems, Biochemistry, And Life In A Warming World [Mark Ritchie's 2021 SFI Seminar + @SFIscience Twitter thread on Mark's talk]Scale and information-processing thresholds in Holocene social evolutionby Jaeweon Shin, Michael Holton Price, David H. Wolpert, Hajime Shimao, Brendan Tracey & Timothy A. KohlerGeneralized Stoichiometry and Biogeochemistry for Astrobiological Applicationsby Christopher P. Kempes, Michael J. Follows, Hillary Smith, Heather Graham, Christopher H. House & Simon A. Levin Complexity 4: Luis Bettencourt on The Science of CitiesComplexity 5: Jennifer Dunne on Food Webs & ArchaeoEcologyComplexity 17: Chris Kempes on The Physical Constraints on Life & EvolutionComplexity 35: Scaling Laws & Social Networks in The Time of COVID-19 with Geoffrey WestComplexity 41: Natalie Grefenstette on Agnostic Biosignature DetectionAlien Crash Site 15: Cole Mathis on Pathway Assembly and AstrobiologyPodcast theme music by Mitch Mignano.Cover artwork adapted from photos by Peter Nguyen and Torsten Wittmann (UCSF).

Deep inside your cells, the chemistry of life is hard at work to make the raw materials and channel the energy required for growth, maintenance, and reproduction. Few systems are as intricate or as mysterious. For this reason, how a cell does what it does remains a frontier for research — and, consequently, theory often grows unchecked by solid data. Most of what we know about the enzymatic processes of plant and animal metabolisms comes from test tube experiments, not studies in the context of a living organism. How much has this necessarily reductionist approach misled us, and what changes when we zoom out and think about life's manufacturing and distribution in situ?Welcome to COMPLEXITY, the official podcast of the Santa Fe Institute. I'm your host, Michael Garfield, and every other week we'll bring you with us for far-ranging conversations with our worldwide network of rigorous researchers developing new frameworks to explain the deepest mysteries of the universe.This week we open a two-part discussion with ecologist Mark Ritchie of Syracuse University on how he and his SFI collaborators are starting to rethink the intersections of thermodynamics and biology to better fit our scientific models to the patterns we observe in nature. Beginning with his history of research into biodiversity, environmental science, and plant-herbivore dynamics, this conversation leads us to his latest work on photosynthesis and scaling laws in cells — an inquiry with potent implications that reach far beyond the microscopic realm, to economics and the future of sustainability.Subscribe to stay tuned for Part Two, in which we travel even deeper into how Mark's work relates to other SFI research — and what his new perspectives may reveal about the nature of the complex crises faced by both human beings and the biosphere at large...If you value our research and communication efforts, please rate and review us at Apple Podcasts, and/or consider making a donation at santafe.edu/podcastgive. You can find numerous other ways to engage with us at santafe.edu/engage. Thank you for listening!Join our Facebook discussion group to meet like minds and talk about each episode.Podcast theme music by Mitch Mignano.Follow us on social media:Twitter • YouTube • Facebook • Instagram • LinkedInRelated Reading & Listening:Ritchie Lab at Syracuse University | Mark's Google Scholar Page | Mark's soil ecology startupReaction and diffusion thermodynamics explain optimal temperatures of biochemical reactions by Mark Ritchie in Scientific ReportsThermodynamics Of Far From Equilibrium Systems, Biochemistry, And Life In A Warming World [Mark Ritchie's 2021 SFI Seminar + @SFIscience Twitter thread on Mark's talk]Complexity Podcast 17: Chris Kempes on The Physical Constraints on Life & EvolutionComplexity Podcast 35: Scaling Laws & Social Networks in The Time of COVID-19 with Geoffrey WestMentioned in this episode:Sidney RednerGeoffrey WestJohn HartePablo MarquetJennifer DunneBrian ArthurChris Kempes

My AP Biology Thoughts  Unit 2 Cell Structure and FunctionWelcome to My AP Biology Thoughts podcast, my name is Nidhi and I am your host for episode #51 called Unit 2 Cell Structure and Function: Comparing the Energy Related Organelles. Today we will be discussing the similarities and differences between the mitochondria and chloroplast.  Segment 1: Introduction to the energy related organelles Both eukaryotes and prokaryote cells need energy to function. Eukaryotes rely on the mitochondria and chloroplast to provide their cell with energy. The Mitochondria and the chloroplast also both contain their own DNA and are able to grow and reproduce independently within the cell. Mitochondria are found in plant and animal cells while chloroplasts are found only in plant cells. The mitochondria work to convert oxygen and nutrients into ATP through a process known as cellular respiration. Without a mitochondrion, many animals would not exist because they would not be able to obtain enough energy. The mitochondria enable cells to produce 15 times more ATP than they could otherwise. The number of mitochondria in a cell depends on the metabolic requirements of that cell. They were first discovered in the 1800s but until the 1950s they were believed to transmit hereditary information. In contrast, the chloroplast produces energy through photosynthesis. It has a high concentration of chlorophyll, the molecule that captures light energy, and this gives many plants green color. Chloroplasts are essential for the growth and survival of plants and photosynthetic algae. Chloroplasts take light energy and convert it into energy stored in the form of sugar and other organic materials. Cells need both chloroplasts and mitochondria to undergo both photosynthesis and cell respiration. After photosynthesis, which occurs through the chloroplast, that produces oxygen and glucose, plants need to break down the glucose and they use cellular respiration to do this, which happens in the mitochondria. There Is one plant that does not have a chloroplast, Rafflesia, which obtains its nutrients from other plants. Since it gets all of its energy from parasitizing another plant, it no longer needs its chloroplasts, and has lost the genes coding for the development of the it. Segment 2: More About the the Mitochondria and Chloroplasts There are many similarities and differences between the structures of the 2 organelles. Mitochondria have an inner and outer membrane, with an intermembrane space between them. The outer membrane contains proteins known as porins, which allow the movement of ions into and out of the mitochondrion. The space within the inner membrane of the mitochondria is known as the matrix, which contains the enzymes of the Krebs and fatty acid cycles, alongside DNA, RNA, ribosomes and calcium granules. The inner membrane contains a variety of enzymes. It contains ATP synthase which generates ATP in the matrix, and transport proteins that regulate the movement of molecules into and out of the matrix. The inner membrane is arranged into folds known as cristae in order to increase the surface area available for energy production. Chloroplasts are surrounded by a double membrane similar to the double membrane found within a mitochondrion. Within the chloroplast is a third membrane that forms stacked, disc-shaped structures called thylakoids. Embedded in the thylakoid membrane are molecules of chlorophyll. A stack of thylakoids is called a granum, and the space surrounding the granum is called the stroma. Just like the structure of the mitochondria was important to its ability to perform aerobic cellular respiration, the structure of the chloroplast allows the process of photosynthesis to take place. Segment 3: Connection to the CourseThe mitochondria and chloroplast can be connected to the greater theme of cell organelle functions and the endosymbiotic theory. The similar function of the mitochondria and...

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Learn about why you can BS a BS-er; how you can get your hands on some of the world’s oldest books at the Thomas Fisher Rare Book Library; and a sea slug in the genus Elysia that cuts off its own head when it wants a new body.  You *can* BS a BSer — but it depends on the kind of BS by Steffie Drucker It Turns Out You Can Bullshit A Bullshitter After All. (2021, March 5). Research Digest; Research Digest. https://digest.bps.org.uk/2021/03/05/it-turns-out-you-can-bullshit-a-bullshitter-after-all/  Littrell, S., Risko, E. F., & Fugelsang, J. A. (2021). “You can’t bullshit a bullshitter” (or can you?): Bullshitting frequency predicts receptivity to various types of misleading information. British Journal of Social Psychology. https://doi.org/10.1111/bjso.12447  Research shows that BSers are more likely to fall for BS. (2021). EurekAlert! https://www.eurekalert.org/pub_releases/2021-03/uow-rst030821.php  You Can Encounter Some of the World's Oldest Books at the Thomas Fisher Rare Book Library by Reuben Westmaas Thomas Fisher Rare Book Library. (2020). Thomas Fisher Rare Book Library. https://fisher.library.utoronto.ca/  Thomas Fisher Rare Book Library. (2015, June 8). Atlas Obscura. https://www.atlasobscura.com/places/thomas-fisher-rare-books-library  Monstorum historia (1642). Pinterest. https://www.pinterest.com/poppadoug/monstrorum-historia-1642-ulyssis-aldrovandi/  There's a slug that cuts off its own head when it wants a new body by Cameron Duke Meet the Sea Slugs That Chop Off Their Heads and Grow New Bodies. (2021). The New York Times. https://www.nytimes.com/2021/03/08/science/decapitated-sea-slugs.html  Mitoh, S., & Yusa, Y. (2021). Extreme autotomy and whole-body regeneration in photosynthetic sea slugs. Current Biology, 31(5), R233–R234. https://doi.org/10.1016/j.cub.2021.01.014  Follow Curiosity Daily to learn something new every day withCody Gough andAshley Hamer — for free! You can also listen to our podcast as part of your Alexa Flash Briefing; Amazon smart speakers users, click/tap “enable” here:https://www.amazon.com/Curiosity-com-Curiosity-Daily-from/dp/B07CP17DJY See omnystudio.com/listener for privacy information.

Give all your Biology assignment help online queries a strategic direction by diverting your problems to My Assignment Services. Our experts providing you with the best Biology assignment help Australia are capable of assisting with the terms and terminologies such as Ribosomes, RNA, Lysosomes. Chloroplasts, Vacuoles, Endoplasmic Reticulum, and much more. We have more than 400 Biology assignment help experts who are there with us and have more than 12 experience in the corresponding discipline. By choosing our assignment help experts, you get a chance to prepare a 100% original and plagiarism free assessment tasks at a minimal price.

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.01.277616v1?rss=1 Authors: Castillo, M. A., Wardley, W. P., Lopez-Garcia, M. Abstract: Chloroplasts, the organelles responsible for photosynthesis in most plants and algae, exhibit a variety of morphological adaption strategies to changing light environments which can have important yet overlooked light scattering effects. This can be even more significant for iridoplasts, specialized chloroplasts whose tissue is arranged as a photonic multilayer producing a characteristic strong blue reflectance associated to a wavelength selective absorption enhancement relevant for photosynthesis. In this work, we study how the photonic properties of iridoplasts are affected by light induced dynamic changes using realistic data extracted from previous reports. Our results show a reflectance red-shift from blue to green under increasing light intensity. Consequently, the light absorption enhancement induced by the photonic nanostructure is also redshifted. We also show that the photonic properties are resilient to biologically realistic levels of disorder in the structure. We extended this analysis to another photonic nanostructure-containing chloroplast, known as a bisonoplast, and found similar results, pointing towards similar properties in different plant species. We finally found that all types of chloroplasts can tune light absorption depending on light conditions. In general, our study opens the door to understanding how dynamic morphologies in chloroplasts can affect light scattering and absorption. Copy rights belong to original authors. Visit the link for more info

Peering into a drop of pondwater allows you to look back in time and see key events in the history of life on Earth. In this episode we learn where plants obtained the machinery needed for photosynthesis and find out how hard it is for multicellular beings to form.

Episode 34 finds the similarities and differences between chloroplasts and mitochondria. The endosymbiosis theory states that these energy transducers were once independent prokaryotes (1:38). Chloroplasts capture light energy in photosynthesis (2:20). Mitochondria break down sugars in cellular respiration (4:00). There are many commonalities between each organelle’s structure and function.The Question of the Day asks (6:35) “What are the alternate names for the Krebs cycle”?Thank you for listening to The APsolute RecAP: Biology Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2020 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTER

Today we celebrate the one year anniversary of the show and the man who wrote a flora of the Middle East. We'll learn about the German botanist who discovered mitosis and chloroplasts. We celebrate the 93rd birthday of an English-Australian gardener who learned to garden and survived during World War II. We'll honor the tremendous work of Kenya's garden activist and founder of the Green Belt Movement. Today's Unearthed Words feature words about April. We Grow That Garden Library™ with a book that was released 16 years ago today. And then, we'll wrap things up with the fascinating story of a whiskey baron who used his wealth to create an arboretum that is home to America's largest collection of Holly trees. But first, let's catch up on some Greetings from Gardeners Around the World and today's curated news.   Subscribe Apple | Google | Spotify | Stitcher | iHeart   Gardener Greetings Well, it's hard to believe that the show is already a year old. I started the show on April 1st because this month's name came from the Latin word aperio, meaning "to open [bud]," - so it was the perfect time to start something new. Plants outside and in are really beginning to grow now. Daisy and Sweet Pea are this month's birth flowers. To participate in the Gardener Greetings segment, send your garden pics, stories, birthday wishes and so forth to Jennifer@theDailyGardener.org And, to listen to the show while you're at home, just ask Alexa or Google to play The Daily Gardener Podcast. It's that easy.   Curated News In chaotic times, gardening becomes therapy | Cleveland.com "As spring's arrival in the Northern Hemisphere coincides with government stay-at-home orders, the itch to get outside has turned backyard gardens into a getaway for the mind in chaotic times. Gardeners who already know that working with soil is a way to connect with nature say it helps take away their worries, at least temporarily. "I love to see things grow," Lindsay Waldrop said. "It's incredibly therapeutic." Families, too, are discovering that gardening gives cooped-up kids something to do, builds their self-esteem and brings variety to what has suddenly become a lot of time spent together. This home-grown attitude goes back to World War II when millions of people cultivated victory gardens to protect against potential food shortages while boosting patriotism and morale. Hollie Niblett, who lives near Kansas City, Kansas, hopes the victory gardens come back. Niblett, who has a degree in horticultural therapy, tends to a kitchen garden near her backdoor, perennial flowers, flowering trees and shrubs, and upper and lower grassy yards connected by a path through an area left in its natural condition. "There are so many things about it that feed my soul," she said. "Right now, more than anything, my garden gives me hope, gives me purpose, and provides a sense of connection to something bigger than myself."   811 - Call Before You Dig - And, right now - Don't. Add 811 in your phone contacts. Save it under "Digging." In the notes, add a reminder to call at least three days before you dig. Alright, that's it for today's gardening news. Now, if you'd like to check out my curated news articles and blog posts for yourself, you're in luck, because I share all of it with the Listener Community in the Free Facebook Group - The Daily Gardener Community. There's no need to take notes or search for links - the next time you're on Facebook, search for Daily Gardener Community and request to join. I'd love to meet you in the group.   Important Events 1838  Today is the birthday of George Edward Post. We remember George because he wrote a Flora of the Middle East. Westerners were delighted because, for the first time, it was written in English, and they could understand it. George botanized in Syria, which is where he lived most of his life. He was in Syria, serving as a missionary and doctor. In his spare time, he would be off collecting plants and working on his Flora. George was a man who had tremendous energy and stamina. He worked long hours, and many colleagues acknowledged that he accomplished more than most folks in a 24-hour period. In his personal life, it turns out that George had the ability to fall asleep quickly, which no doubt helped him recharge on-demand and as needed. One account of George's tremendous lust for life and for plant collecting relayed that he would go off into the mountains on horseback. The story goes that George was such a good horseman, he could collect specimens without getting off his horse. He was allegedly able to lean below his saddle and reach way down to cut and collect a specimen. Then, he'd just sit back up and go on his way. At the end of his life, George was aware that his body was worn out, and he said something to that effect in the days before he died. Around that same time, he received a visitor who knew just how to revive his spirits. The guest placed a few pieces of ripe wheat in his hand as a symbol of the harvest and of the specimens George had spent a lifetime studying. It also served as a reminder of the treasured bible passage: "To everything, there is a season, and a time to every purpose under the heaven: A time to be born, and a time to die; a time to plant, and a time to pluck up that which is planted."   1805  Today is the birthday of the German botanist Hugo von Mohl. The greatest "botanist of his day," it said in one newspaper. A German botanist, he was the first to propose that new cells are formed by cell division. Mitosis was discovered by Hugo von Mohl. And, in 1837, he discovered chloroplasts - something von Mohl called Chlorophyllkörnen, which translates to "a grain a chlorophyll." Forty-seven years later, the Polish-German botanist Eduard Strasburger shortened the term Chlorophyllkörnen to Chloroplast. Von Mohl described chloroplasts as discrete bodies within the green plant cell. Today we know that chloroplasts are the food producers of the cell. Chloroplasts are only found in plant cells, and they convert light energy from the sun into sugar; so without chloroplasts, there would be no photosynthesis. In 1846, von Mohl described the sap in plant cells as "the living substance of the cell," and he also created the word "protoplasm."   1927  Today is the 93rd birthday of English-born Australian horticulturalist, conservationist, author, broadcaster, and television personality Peter Cundall. A Tasmanian gardener, Peter was the friendly host of the long-running TV show Gardening Australia - one of the first shows committed to 100% organic practices and practical advice. Peter inspired both young and old to the garden. In his epic "lemon tree episode," Peter got a little carried away and essentially finished pruning when the tree was little more than a stump. Thereafter, Cundallisation was synonymous with over-pruning. Peter learned to garden as a little boy. His first garden was a vegetable patch on top of an air raid shelter in Manchester, England. His family was impoverished. His father was an abusive alcoholic. Two of his siblings died of malnutrition. Through it all, the garden brought stability, nourishment, and reprieve. Of that time, Peter's recalls, "Lying in bed in the morning waiting for it to be light, so I could go out and get going in my garden. I used to think there was some gas given out by the soil that produced happiness."   1940  Today is the birthday of the Kenyan ecologist and first female Kenyan Ph.D. and professor Wangari Maathai ("One-Garry" - rhymes with starry - "Ma-TH-EYE") Wangari was the founder of the Green Belt Movement. She fought for environmental protection and women's empowerment by working with communities to plant "green belts" of trees. Today, the Green Belt Movement has planted "over 45 million trees across Kenya to combat deforestation, stop soil erosion, and generate income for women and their families." In 2004, Wangari became the first African woman to win the Nobel Peace Prize. The Nobel committee recognized "her contribution to sustainable development, democracy, and peace." Wangari authored four books: The Green Belt Movement, Unbowed: A Memoir; The Challenge for Africa; and Replenishing the Earth. Wangari died from ovarian cancer in 2011 at the age of 71. Wangari said, "We think that diamonds are very important, gold is very important, all these minerals are very important. We call them precious minerals, but they are all forms of the soil. But that part of this mineral that is on top, like it is the skin of the earth, that is the most precious of the commons." "Using trees as a symbol of peace is in keeping with a widespread African tradition. For example, the elders of the Kikuyu carried a staff from the thigi tree that, when placed between two disputing sides, caused them to stop fighting and seek reconciliation. Many communities in Africa have these traditions." "When we plant trees, we plant the seeds of peace and hope."   Unearthed Words Here are some poignant words about this time of year.   The first of April is the day we remember what we are the other 364 days of the year. — Mark Twain, American writer & humorist   "The first of April, some do say, Is set apart for All Fools' Day. But why the people call it so, Nor I, nor they themselves do know. But on this day are people sent On purpose for pure merriment." — Poor Robin's Almanac, 1790   The April winds are magical, And thrill our tuneful frames; The garden walks are passional To bachelors and dames." ― Ralph Waldo Emerson, American essayist and poet   Men are April when they woo,  December when they wed;  Maids are May when they are maids,  but the sky changes when they are wives. — Shakespeare, As You Like It, Act IV Scene 1   "[W] ell-apparell'd April on the heel Of limping winter treads…" — Shakespeare, Romeo and Juliet, Act 1 Scene 2    Grow That Garden Library On the Wild Side by Keith Wiley It's hard to believe that this book was published on this day already sixteen years ago in 2004. The subtitle to this book is "Experiments in the New Naturalism." Keith created his own wild garden in the early 2000s after being inspired by rural England. He also discovered an entire world of influence as he studied New England roadsides, the Colorado Rockies, Swiss Alpine Meadows, and the South African savannas. In this book, Keith strives to capture "only the spirit of wild plantings and never attempt to replicate exactly any landscape or combination of plants." Keith has learned to focus on form, color, and placement of plants. His attention to detail is what makes his approach work so well. Keith was an early advocate of grouping plants into plant communities. He loves it when plants self-seed - especially when they create beauty in unanticipated ways. Keith's book shares many of his favorite plants and plant groupings. He offers tons of advice and ideas for gardens. in this book, he's hoping to inspire us to get creative, "freeing your own creative inner spirit from the straitjacket of horticultural tradition." You can get a used copy of On the Wild Side by Keith Wiley and support the show, using the Amazon Link in today's Show Notes for under $8.   Today's Botanic Spark 1945  Today is the anniversary of the death of American businessman Isaac Wolfe Bernheim. Bernheim made a fortune selling and distilling whiskey - and in turn, he used some of his wealth to create the Bernheim Arboretum and Research Forest. In 1931, the Frederick Law Olmsted firm was asked to design the park. They created roadways, paths, and natural areas, planted trees, and turned the farmland back into meadows, lawns, and forest. Sparing no expense, Bernheim provided the capital to add lakes, rivers, and ponds for "an enlivening effect." Nineteen years later, in 1950, the Bernheim Forest officially opened and was ultimately given to the people of Kentucky in trust. Bernheim is the largest privately-owned natural area in Kentucky. Today, the arboretum's holly collection is among the best in North America, with more than 700 specimens representing over 350 individual species and cultivars. Love is like the wild rose-brier; Friendship like the holly tree. The holly is dark when the rose-brier blooms, But which will bloom most constantly? — Emily Brontë, author The holly collection features 176 American Holly (Ilex opaca), 44 Japanese Holly (Ilex crenata), over 50 deciduous hollies (Ilex decidua, Ilex verticillata, Ilex serrata, and hybrids), and 19 cultivars of Inkberry (Ilex glabra) - as well as many specialty hybrids. The arboretum is also home to maples, crab apples, conifers (including dwarf conifers), oaks, buckeyes, ginkgoes, ornamental pears and dogwoods. There is also a sun and shade trail, a quiet garden, and a garden pavilion. By 1994, the State of Kentucky made Bernheim the state's official arboretum. A true visionary, Bernheim wrote that "nothing is static in this world." He appreciated that the natural world was constantly going through continuous change. He believed that people needed to spend time connecting with nature. In August of 1939, Bernheim set up some conditions for his forest in a letter to the trustees, and he proposed the following rules for the forest: No discussion of religion or politics, no trading or trafficking. . . No distinction will be shown between rich or poor, white or colored. My vision embraces an edifice, beautiful in design,... It may be made of marble or of native stone. . . . Within it, there will be an art gallery . . . . Therein there will be busts in bronze of men and women whose names have risen to places of distinctive honor in Kentucky. A museum of natural history containing specimens of every animal … of this hemisphere... . . . a tall steel pole … will float the American Flag… [and] children… will be told the story of liberty. To all, I send the invitation to come . . . to re-create their lives in the enjoyment of nature . . . in the park which I have dedicated ... and which I hope will be kept forever free.  

Algae. It's one of the greatest things on the planet and it's responsible for all life on Earth, including your life. But how much do you really know about this incredible species? Is it a plant? Why is it green? Can you eat it? Can we make it into fuel? What's up with algae blooms? Learn more in our newest episode where we talk about the benefits of algae and how it is better than human. Follow us on Twitter @betterthanhuma1on Facebook @betterthanhumanpodcaston Instagram @betterthanhumanpodcastOr email us at betterthanhumanpodcast@gmail.comWe look forward to hearing from you, and we look forward to you joining our cult of weirdness.

I am joined in the Lair this week by Author Danielle Ancona. We talk about Chloroplasts and more! Website: https://danielleancona.com/

Cat, Nick and Tim bring you this week’s serve of Boiling Point Science: Shy but deadly – the secrets behind the toxin that makes the blue ringed octopus so dangerous Blood sugar too high ? – how researchers turn stem cells into insulin-producing pancreas cells Green and aggressive – chloroplasts are capable of much more […]

This week, Mark has a conundrum about chloroplasts: If we could go green and harvest energy from the sun, like plants, how big would our skin need to be to sustain a normal level of activity? Georgia Mills recruited Christopher Mason, associate professor at Weill Cornell Medicine to shed some light on the answer. Like this podcast? Please help us by supporting the Naked Scientists

Tue, 15 Jul 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18552/ https://edoc.ub.uni-muenchen.de/18552/1/Schock_Annette.pdf Schock, Annette ddc:570, ddc:500, Fakultät für Biologie

Fri, 9 Aug 2013 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18566/ https://edoc.ub.uni-muenchen.de/18566/1/Wang_Jing.pdf Wang, Jing ddc:570, ddc:500, Fakultät für Biologie

Fri, 5 Oct 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/14904/ https://edoc.ub.uni-muenchen.de/14904/1/Studte_Carsten.pdf Studte, Carsten ddc:570, ddc:500, Fakultät

Tue, 17 Jul 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/15332/ https://edoc.ub.uni-muenchen.de/15332/1/Gomes_Rocha_Agostinho.pdf Gomes Rocha, Agostinho Manuel

Most chloroplast proteins are encoded for in the nucleus and have to be transported into the organelle after translation in the cytoplasm. The TOC and TIC machineries (Translocon at the Outer/Inner envelope membrane of Chloroplasts) mediate the import of these proteins across the chloroplast membranes. The major aim of this work was to characterize two TIC translocon components: Tic110, the main protein translocation channel in the inner envelope, and Tic20, which was proposed to also form a protein import channel. After a detailed study of Tic110, a topological model could be established, demonstrating that the protein is inserted into the membrane with two hydrophobic and four amphipathic helices, placing residues both to the intermembrane space and to the stromal side. The presence of highly conserved cysteine residues and experiments demonstrating that Tic110 possess a redox active disulfide bridge, which could be reduced by stromal thioredoxins in vitro, indicated that Tic110 might be a possible target for thioredoxin regulation. To explore which cysteines are involved in disulfide bridge formation, mutations were generated for conserved cysteines in Tic110. As a result, Cys492 and Cys890 were identified as possible candidates. To define the functional role of disulfide bridge(s), components of the TIC motor complex were overexpressed and purified and their interaction was analysed with Tic110 via different approaches. The second part of this work focuses on the channel activity of Tic20. Although both Tic110 and Tic20 are clearly important for plant viability and preprotein translocation, there were neither electrophysiological nor biochemical data supporting that Tic20 can form a channel. After inserting the heterologously overexpressed and purified protein into liposomes, swelling assays and electrophysiological measurements provided the first experimental evidence for the channel activity of Tic20, being a cation selective channel with a pore size of about 8-14 Å. Therefore, it was concluded that the TIC translocon consists of at least two distinct translocation channels: Firstly, Tic110 forms the main translocation pore and therefore facilitates import of most of the chloroplast-targeted preproteins. Secondly, Tic20 might be specifically required for the translocation of some possibly essential proteins. To gain further insight into the structure and function of both proteins, preliminary tests were performed for crystallization in lipidic phases. The large sample of grown crystals observed under different conditions will presumably enable to crystallize these proteins and resolve their crystal structures in the future.

The vast majority of chloroplast proteins is encoded in the nucleus and thus has to be posttranslationally imported into the organelle, a process that is facilitated by two multimeric protein machineries, the Toc and Tic complexes (translocon at the outer/inner envelope of chloroplasts). Regulation of protein import, e.g. by redox signals, is a crucial step to adapt the protein content to the biochemical requirements of the organelle. In particular, one subunit of the Tic complex, Tic62, has been proposed as a redox sensor, whose possible function is to regulate protein import by sensing and reacting to the redox state of the organelle. To elucidate a potential redox regulation of protein import, structural features, redox-dependent properties and the evolutional origin of Tic62 were investigated. The results show that Tic62 consists of two very different modules: the N-terminal part was found to be mainly -helical and possesses dehydrogenase activity in vitro. It is furthermore an evolutionary ancient domain, as it is highly conserved in all photosynthetic organisms from flowering plants to cyanobacteria and even green sulfur bacteria. In contrast to this, the C-terminus is largely disordered and interacts specifically with ferredoxin-NADP+ oxidoreductase (FNR), a key enzyme in photosynthetic electron transfer reactions. Moreover, this domain was found to exist only in flowering plants, and thus the full-length Tic62 protein seems to be one of the evolutionary youngest Tic components. The results of this study make also clear that Tic62 is a target of redox regulation itself, as its localization and interaction properties depend on the metabolic redox state: oxidized conditions lead to fast membrane binding and interaction with the Tic complex, whereas reduced conditions cause solubilization of Tic62 into the stroma and increased interaction with FNR. This novel shuttling behaviour indicates a dynamic composition of the Tic complex. The NADP+/NADPH ratio was furthermore found to be able to influence the import efficiency of many precursor proteins. Interestingly, the import of not all preproteins depends on the stromal redox state. Hence it was proposed that not a single stable Tic translocon exists, but several Tic subcomplexes with different subunit compositions, which might mediate the import of different precursor groups in a redox-dependent or -independent fashion. Another redox signal that was analyzed in regard to an impact on protein import is the reversible reduction of disulfide bridges, which was found to affect the channel and receptor proteins of the Toc complex. The import of all proteins that use the Toc translocon for entering the chloroplast was shown to be influenced by disulfide bridge formation. Thus it can be concluded that a variety of redox signals, acting both on the Toc and Tic complexes, are able to influence chloroplast protein import.

Most of the proteins localized in the chloroplast inner envelope membrane are synthesized on cytosolic ribosomes with a cleavable N-terminal chloroplast transit peptide. Most of them reach their final localization via the so called general import pathway consisting of the Toc complex at the chloroplast outer envelope membrane and the Tic complex at the chloroplast inner envelope membrane. Recent studies characterized precursor proteins which are targeted into the chloroplast inner envelope membrane by two different import pathways. The first route, called “conservative sorting”, was described for Tic40 and Tic110, which prior to inner envelope membrane insertion reach the stroma. The second route, called “stop-transfer” was proposed for ARC6, which is arrested at the level of the inner envelope membrane and probably laterally inserted into the lipid bilayer. Taking into consideration both import mechanisms we characterized import pathways of nine chloroplast inner envelope membrane proteins containing cleavable transit peptides and a different number of hydrophobic -helices. On the basis of the results observed in the stromal processing assays as well as results obtained in the pulse-chase experiments, within investigated precursor proteins two classes could be distinguished. The first class consisted of precursors processed once to their mature forms, i.e. containing a “single” transit peptide, whereas the second class consisted of precursors processed twice to the intermediate and the mature form, i.e. containing a bipartite transit peptide. In the processing of almost all precursor proteins stromal processing peptidase (SPP) was involved. Most probably at least one protein containing a bipartite transit peptide was also processed by another peptidase present not in the stromal compartment. We showed that despite of the differences in the number of hydrophobic transmembrane segments and different types of transit peptides, all investigated proteins had similar import properties. Their import was dependent on outer envelope membrane receptors and mediated by the general import pathway at least in the initial import phase. All investigated proteins required energy for import. 200 M ATP was sufficient for proteins used in this study to achieve the maximal import rate. Interestingly, neither intermediates nor mature proteins were extractable from the membrane by urea treatment and all proteins seemed not to possess a soluble import intermediate. Therefore we claim that all investigated precursor proteins were imported via the “stop-transfer” pathway. Moreover, most probably at least some components of the Tic complex were involved in the transport of precursor proteins at the level of the inner envelope membrane and the process was Ca2+/calmodulin regulated.

Nisbet, E (Cambridge) Thursday 20 December 2007, 14:00-14:20 PLGw03 - Future Directions in Phylogenetic Methods and Models

Lockhart, P (Massey) Thursday 06 December 2007, 13:00-14:00 Spitalfields Day - Yggdrasil: Reconstructing the Tree of Life

Import of a hybrid construct consisting of the transit sequence of SSU, the N-proximal part of mature Tic110 and the mature SSU into chloroplasts led to the appearance of a soluble stromal import intermediate and the proposal that Tic110 might use a re-export pathway from the stroma to the inner envelope membrane. For full length Tic110 no soluble intermediate has been observed yet. One of the goals of this work was to investigate the import pathway of Tic110 in more detail. In this research the soluble stromal intermediate of Tic110 was observed, its re-export to the membrane was followed, and finally, the intermediate was isolated and co-immunoprecipitated with the stromal chaperones Hsp93, Hsp70 and to a lesser extent Cpn60. The obtained results indicate that Tic110, as proposed, uses a re-export pathway (conservative sorting) during its import into the chloroplast inner envelope membrane. Tic110 also requires stromal chaperones for achieving its native conformation, prior to the insertion into the inner envelope membrane. The pathway for targeting to the intermembrane space of chloroplasts had not been intensively studied yet. For this reason, the analysis of two intermembrane space localized proteins was conducted: Tic22, a 22 kDa Tic-complex protein component, and MGD1, synthase of MGDG, the most abundant galactolipid in nature. Both proteins are nuclear-encoded and synthesized on cytosolic ribosomes with a cleavable N?terminal chloroplast targeting presequence. Tic22 was found to be associated with the outer face of the inner envelope membrane, as well as with the inner face of the outer envelope membrane, even though at a lower level. MGD1 was proposed to be associated with one of the envelopes by weak electrostatic interactions. Import properties of Tic22 and MGD1 and the localization of MGD1 were investigated in this research. Results presented in this thesis show that import of MGD1 is dependent on, and that of Tic22 is enhanced by, but not dependent on, addition of external ATP. Both preproteins need thermolysin sensitive components on the chloroplast surface for successful import. Chemical crosslinking and immunoprecipitation have demonstrated that Tic22 and MGD1 interact with the components of the Toc translocon of the chloroplast outer envelope during their translocation. Import competition experiments showed that both proteins use the Toc machinery of the general import pathway. Therefore, proteins targeted to the intermembrane space seem to use the same translocation mode across the outer envelope as stromal proteins.

The first step of preprotein translocation across the membranes of chloroplasts is facilitated by the Toc translocon. Aim of this work was to elucidate the dynamics and the mechanism of action of this molecular machine. The central, stably associated part of the Toc translocon, the Toc core complex, consists of the pore forming Toc75 and two receptors with GTPase activity, Toc34 and Toc159. The question of Toc159 localization was addressed since controversal results on this topic were reported. In this study, membrane localization of Toc159 was confirmed, which has further implications on the mode of its action. To understand the necessity of multiple isoforms of Toc components as found in Arabidopsis thaliana, expression analysis and tissue-specific localization were conducted. Gathered data suggested the existence of several types of the complex, assembled from different types of subunits. These complexes have different preprotein specificities. Expression analysis provided further arguments for dynamic association of the intermembrane space complex with the Toc core complex. Comparison of gene expression and protein presence of translocon subunits contradicts the function of Tic20 as a general pore for stromal targeted proteins, but not as a protein conducting channel per se. For further analysis of the Toc translocon structure and function, its purification and reconstitution into proteoliposomes was reinvestigated. To this end, a technique for liposome size determination in a single spectrophotometric measurement was developed.

The vesicle inducing protein in plastids 1 (Vipp1) is an essential factor for the development and maintenance of the thylakoid membrane. Depletion of Vipp1 in both Arabidopsis and Synechocystis mutants severely affects their ability to form thylakoids and consequently to perform photosynthesis. This work focuses on structural and functional properties of Vipp1. It was shown that Vipp1 assembles into a homooligomeric complex of ca. 2000 kDa. The presence of the Vipp1 complex was detected in cyanobacteria, green algae and higher plants, thereby identifying oligomerization as an essential feature for the function of Vipp1. A detailed computer analysis of Vipp1 secondary structure in different organisms revealed functionally important characteristics of the protein and allowed to discern specific features of its C-terminal domain. Based on the structural analysis, biochemical characterization of Vipp1 domains was carried out. It appeared that the PspA-like domain of Vipp1 is responsible for both complex formation and localisation of Vipp1 at the inner envelope of chloroplasts while the C-terminal domain is not involved in these processes. In order to closer elucidate the function of Vipp1, an analysis of Arabidopsis plants with moderate deficiency in Vipp1 protein level was performed. From results obtained in this analysis it can be proposed that Vipp1 acts at the initial stages of thylakoid biogenesis. Oligomerization of Vipp1 appeared to be a prerequisite for the process of thylakoid formation to commence. Moreover, the extent of thylakoid membrane formation is directly correlated to the amount of Vipp1 protein available in the chloroplast.

Sun, 1 Jan 1995 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3583/ http://epub.ub.uni-muenchen.de/3583/1/3583.pdf Soll, Jürgen; Seedorf, M. Mathis, Paul (Hrsg.) (1995): The protein import machinery of chloroplasts. International Congress on Photosynthesis , 20 - 25 August 1995, Montpellier. Biologie

Routing of cytosolically synthesized precursor proteins into chloroplasts is a specific process which involves a multitude of soluble and membrane components. In this review we wil1 focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins and compare import routes for polypeptide of the outer chloroplast envelope to that of internal chloroplast compartments. A number of proteins housed in the chloroplast envelopes have been implied to be involved in the translocation process, but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import competence of a precursor protein in transit into the organelle.

Fri, 1 Jan 1993 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3592/ http://epub.ub.uni-muenchen.de/3592/1/3592.pdf Waegemann, Karin; Soll, Jürgen Morré, D. James (Hrsg.) (1993): Isolation and characterization of a functionally active protein translocation apparatus from chloroplasts envelopes. NATO Advanced Research Workshop on Cell Free Analysis of the Functional Organization of the Cytoplasm , May 9 - 13, 1992], Arlie, Virginia USA.

Fri, 1 Jan 1993 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3465/ http://epub.ub.uni-muenchen.de/3465/1/003.pdf Bertsch, Uwe; Schlicher, Thomas Bernard; Schröder, Inge; Soll, Jürgen Bertsch, Uwe; Schlicher, Thomas Bernard; Schröder, Inge und Soll, Jürgen (1993): Sequence of mature phosphoglycerate kinase from spinach chloroplasts. In: Plant Physiology, Vol. 103, Nr. 4: pp. 1449-1450. Biologie

Chloroplasts of higher plants contain a nuclear-encoded protein that is a functional homolog of the Escherichia coli chaperonin 10 (cpn10; also known as groES). In pea (Pisum sativum), chloroplast cpn10 was identified by its ability to (i) assist bacterial chaperonin 60 (cpn60; also known as groEL) in the ATP-dependent refolding of chemically denatured ribulose-1,5-bisphosphate carboxylase and (ii) form a stable complex with bacterial cpn60 in the presence of Mg.ATP. The subunit size of the pea protein is approximately 24 kDa--about twice the size of bacterial cpn10. A cDNA encoding a spinach (Spinacea oleracea) chloroplast cpn10 was isolated, sequenced, and expressed in vitro. The spinach protein is synthesized as a higher molecular mass precursor and has a typical chloroplast transit peptide. Surprisingly, however, attached to the transit peptide is a single protein, comprised of two distinct cpn10 molecules in tandem. Moreover, both halves of this "double" cpn10 are highly conserved at a number of residues that are present in all cpn10s that have been examined. Upon import into chloroplasts the spinach cpn10 precursor is processed to its mature form of approximately 24 kDa. N-terminal amino acid sequence analysis reveals that the mature pea and spinach cpn10 are identical at 13 of 21 residues.

Wed, 1 Jan 1992 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3594/ http://epub.ub.uni-muenchen.de/3594/1/3594.pdf Soll, Jürgen; Alefsen, H.; Böckler, B.; Kerber, Birgit; Salomon, Michael; Waegemann, Karin Soll, Jürgen; Alefsen, H.; Böckler, B.; Kerber, Birgit; Salomon, Michael und Waegemann, Karin (1992): Comparison of two different translocation mechanisms into chloroplasts. In: Neupert, N. und Lill, R. (Hrsg.), Membrane Biogenesis and Protein Targeting. Springer: Berlin u.a., pp. 299-306. Biologie

Wed, 1 Jan 1992 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3466/ http://epub.ub.uni-muenchen.de/3466/1/004.pdf Soll, Jürgen; Waegemann, Karin Soll, Jürgen und Waegemann, Karin (1992): A funcionally active protein complex from chloroplasts. In: The Plant Journal, Vol. 2: pp. 253-256. Biologie

Outer envelope membranes were isolated from purified chloroplasts of pea leaves. The sidedness of the vesicles was analyzed by (i) aqueous polymer-two phase partitioning, (ii) the effect of limited proteolysis on the outer-envelope proteins (OEP) 86 and OEP 7 in intact organelles and isolated membranes, (iii) fluorescence-microscopy and finally (iv) binding of precursor polypeptides to isolated outer-membrane vesicles. The results demonstrate that purified outer envelope membranes occur largely (>90%) as right-side-out vesicles.

Isolated outer envelope membrane from pea (Pisum sativum L.) chloroplasts can be used in vitro to study binding and partial translocation of precursor proteins destined for the inside of the organelle. Efficient binding to a receptor protein on the outside of the membrane vesicle and generation of a translocation intermediate depends strictly on the presence of ATP. Protease treatment of the translocation intermediate demonstrates its insertion into the membrane. The membraneinserted precursor protein cannot be extracted by 1 M NaCl and is also NaOH resistant to a large extent. Mild solubilization of outer envelope membranes by detergent resulted in the isolation of a complex which still contained the precursor protein. We have identified a constitutively expressed homologue hsc 70 as part of this membrane complex. Antibodies against hsp 70 (inducible heat shock protein 70) were able to immunoprecipitate the complex bound precursor protein. A second protein of 86 kDa molecular weight (OEP 86) from the outer envelope membrane was also identified as a major component of this complex.

The precursor form of the major-harvesting chlorophyll a/b-binding protein (pLHCP) of chloroplast thylakoids was overproduced in E. coli cells and used to study the influence of soluble factors on post-translational protein import into isolated pea chloroplasts. pLHCP solubilised in 8 M urea was not import-competent. However, if pLHCP was dialysed in the presence of soluble proteins (leaf extract) after urea treatment, import competence was gained. Dialysis of pLHCP in the presence of leaf extract alters its protease sensitivity. Stremai proteins, ovalbumin, trypsin inhibitor or chloroplast lipids could not produce import competence of pLHCP. Two components from leaf extract seem to be necessary, one of which can be mimicked by purified hsc 70, the other one requiring ATP. We conclude that soluble proteins from outside the stromal compartment are necessary for post-translational import of proteins into chloroplasts.

A 64-kilodalton (kDa) protein, situated in the lumen between the inner and outer envelopes of pea (Pisum sativum L.) chloroplasts (Soll and Bennett 1988, Eur. J. Biochem., 175, 301–307) is shown to undergo reversible phosphorylation in isolated mixed envelope vesicles. It is the most conspicuously labelled protein after incubation of envelopes with 33 nmol·1-1 [-32P]ATP whereas incubation with 50 mol·1-1 [-32P]ATP labels most prominently two outer envelope proteins (86 and 23 kDa). Half-maximum velocity for phosphorylation of the 64-kDa protein occurs with 200 nmol·1-1 ATP, and around 40 mol·1-1 ATP for phosphorylation of the 86- and 23-kDa proteins, indicating the operation of two distinct kinases. GGuanosine-, uridine-, cytidine 5-triphosphate and AMP are poor inhibitors of the labelling of the 64-kDa protein with [-32P]ATP. On the other hand, ADP has a potent influence on the extent of labelling (half-maximal inhibition at 1–5 mol·1-1). The ADP-dependent appearance of 32P in ATP indicates that ADP acts by reversal of kinase activity and not as a competitive inhibitor. However, the most rapid loss of 32P from pre-labelled 64-kDa protein occurs when envelope vesicles are incubated with ATP t1/2=15 s at 20 molsd1-1 ATP). This induced turnover of phosphate appears to be responsible for the rapid phosphoryl turnover seen in situ.

The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [γ-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [γ-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110000 × g centrifugation.

A guanosine 5-triphosphate (GTP)-dependent protein kinase was detected in preparations of outer chloroplast envelope membranes of pea (Pisum sativum L.) chloroplasts. The protein-kinase activity was capable of phosphorylating several envelope-membrane proteins. The major phosphorylated products were 23- and 32.5-kilo-dalton proteins of the outer envelope membrane. Several other envelope proteins were labeled to a lesser extent. Following acid hydrolysis of the labeled proteins, most of the label was detected as phosphoserine with only minor amounts detected as phosphothreonine. Several criteria were used to distinguish the GTP-dependent protein kinase from an ATP-dependent kinase also present in the outer envelope membrane. The ATP-dependent kinase phosphorylated a very different set of envelope-membrane proteins. Heparin inhibited the GTP-dependent kinase but had little effect upon the ATP-dependent enzyme. The GTP-dependent enzyme accepted phosvitin as an external protein substrate whereas the ATP-dependent enzyme did not. The outer membrane of the chloroplast envelope also contained a phosphotransferase capable of transferring labeled phosphate from [-32P]GTP to ADP to yield (-32P]ATP. Consequently, addition of ADP to a GTP-dependent protein-kinase assay resulted in a switch in the pattern of labeled products from that seen with GTP to that typically seen with ATP.

Thu, 1 Jan 1987 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3512/ http://epub.ub.uni-muenchen.de/3512/1/3512.pdf Schindler, C.; Hracky, R.; Soll, Jürgen Schindler, C.; Hracky, R. und Soll, Jürgen (1987): Protein transport in chloroplasts. ATP is prerequisit. In: Zeitschrift für Naturforschung C, Vol. 42c: pp. 103-108. Biologie

A protein kinase was found in envelope membranes of purified pea (Pisum sativum L.) chloroplasts. Separation of the two envelope membranes showed that most of the enzyme activity was localized in the outer envelope. The kinase was activated by Mg2+ and inhibited by ADP and pyrophosphate. It showed no response to changes in pH in the physiological range (pH 7-8) or conventional protein substrates. Up to ten phosphorylated proteins could be detected in the envelope-membrane fraction. The molecular weights of these proteins, as determined by polyacrylamide-gel electrophoresis were: two proteins higher than 145 kDa, 97, 86, 62, 55, 46, 34 and 14 kDa. The 86-kDa band being the most pronounced. Experiments with separated inner and outer envelopes showed that most labeled proteins are also localized in the outer-envelope fraction. The results indicate a major function of the outer envelope in the communication between the chloroplast and the parent cell.

The prenylquinone content and biosynthetic capabilities of membrane fractions enriched in outer and inner envelope membranes from spinach chloroplasts were analyzed. Both envelope membranes contain prenylquinones, and in almost similar amounts (on a protein basis). However, the outer envelope membrane contains more -tocopherol than the inner one although this prenylquinone is the major one in both fractions. On the contrary, plastoquinone-9 is present in higher amounts in the inner envelope membrane than in the outer one. In addition, it has been demonstrated that all the enzymes involved in the last steps of -tocopherol and plastoquinone-9 biosynthesis i.e., homogentisate decarboxylase polyprenyltransferase, S-adenosyl-methionine: methyl-6-phytylquinol methyltransferase, S-adenosyl-methionine: -tocopherol methyltransferase, homogentisate decarboxylase solanesyltransferase, S-adenosyl-methionine:methyl-6-solanesylquinol methyltransferase, and possibly 2,3-dimethylphytylquinol cyclase, are localized on the inner envelope membrane. These results demonstrate that the inner membrane of the chloroplast envelope plays a key role in chloroplast biogenesis, and especially for the synthesis of the two major plastid prenylquinones.

Tue, 1 Jan 1985 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3516/ http://epub.ub.uni-muenchen.de/3516/1/soll_juergen_3516.pdf Schultz, C.; Soll, Jürgen; Fiedler, Erich; Schultze-Siebert, D. Schultz, C.; Soll, Jürgen; Fiedler, Erich und Schultze-Siebert, D. (1985): Synthesis of prenylquinones in chloroplasts. In: Physiologia Plantarum, Vol. 64, Nr. 1: pp. 123-129. Biologie

Phylloquinol (the quinol form of vitamin K1) is synthesized from 2-phytyl-1,4-naphthoquinol and S-adenosylmethionine at the thylakoid membranes of spinach chloroplasts. The addition of soluble stroma protein (chloroplast extract) is necessary S-Adenosylhomocysteine acts as strong competitive inhibitor.

The reduction of geranylgeranylpyrophosphate to phytylpyrophosphate in spinach chloroplasts is described for the first time. The reductase is localized in the chloroplast envelope. By contrast, the reduction of the geranylgeranyl moiety in Chl synthesis is catalyzed in the thylakoids (via Chl synthetase). NADPH functions as electron donor in both reactions. Chl synthetase is firmly bound to the thylakoid membranes, and very little activity is found in the stroma fraction. Chl synthetase in chloroplasts can use the pyrophosphate ester of either phytol, geranylgeraniol, or farnesol, phytylpyrophosphate being the preferred substrate. Exogenous Chlide exhibits no influence on Chl synthesis by chloroplast subfractions.

Homogentisate is the precursor in the biosynthesis of -tocopherol and plastoquinone-9 in chloroplasts. It is formed of 4-hydroxyphenylpyruvate of the shikimate pathway by the 4-hydroxyphenylpyruvate dioxygenase. In experiments with spinach the dioxygenase was shown to be localized predominatedly in the chloroplasts. Envelope membranes exhibit the highest specific activity, however, because of the high stromal portion of chloroplasts, 60–80% of the total activity is housed in the stroma. The incorporation of 4-hydroxyphenylpyruvate into 2-methyl-6-phytylquinol as the first intermediate in the tocopherol synthesis by the two-step-reaction: 4-Hydroxyphenylpyruvate Homogentisate 2-Methyl-6-phytylquinol was demonstrated by using envelope membranes. Homogentisate originates directly from 4-hydroxyphenylpyruvate of the shikimate pathway. Additionally, a bypass exists in chloroplasts which forms 4-hydroxyphenylpyruvate from tyrosine by an L-amino-acid oxidase of the thylakoids and in peroxisomes by a transaminase reaction. Former results about the dioxygenase in peroxisomes were verified.

Fri, 1 Jan 1982 12:00:00 +0100 https://epub.ub.uni-muenchen.de/5372/1/Zimmermann_Wolfgang_5372.pdf Zimmermann, Wolfgang

Fri, 1 Jan 1982 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3485/ http://epub.ub.uni-muenchen.de/3485/1/033.pdf Soll, Jürgen; Roughan, Grattan Soll, Jürgen und Roughan, Grattan (1982): Acyl—acyl carrier protein and pool sizes during steady-state fatty acid synthesis by isolated spinach chloroplasts. In: FEBS Letters, Vol. 146, Nr. 1: pp. 189-192.

In spinach chloroplasts, 1,4-dihydroxy-2-naphthoate is prenylated by phytyldiphosphate and subsequently methylated by S-adenosylmethionine to form phylloquinol. The site of the prenylation reaction is the chloroplast envelope membrane.

The reduction of /2-14C/-geranylgeranylpyrophosphate to phytylpyrophosphosphate is shown for the first time in chloroplasts. The esterification of exogenous /2-14C/-geranylgeranylpyrophosphate with endogenous chlorophyllide and the stepwise reduction of the pigment bound geranylgeraniol to phytol was also proved for spinach chloroplasts for the first time.

Thu, 1 Jan 1981 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3602/ http://epub.ub.uni-muenchen.de/3602/1/3602.pdf Schultz, Gernot; Bickel, H.; Buchholz, B.; Soll, Jürgen Akoyunoglou, George (Hrsg.) (1981): The plastidic shikimate pathway and its role in the synthesis of plastoquinone-9, α-Tocopherol and phylloquinone in spinach chloroplasts. Fifth International Congress on Photosynthesis , September 7 - 13, 1980, H

The incorporation of [Me-14C] from SAM-[Me-14C] into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) → 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a)→,γ-tocopherol (5a)→-tocopherol (6). 1a is particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phylquinol (2b) to 6 via β-tocopherol (5b). Trimethylphytylquinol (3) is not an intermediate in the formation of 6. All reactions are independent of light.

Tue, 1 Jan 1980 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3488/ http://epub.ub.uni-muenchen.de/3488/1/038.pdf Soll, Jürgen; Douce, Roland; Schultz, Gernot Soll, Jürgen; Douce, Roland und Schultz, Gernot (1980): Site of biosynthesis of a-tocopherol in spinach chloroplasts. In: FEBS Letters, Vol. 112, Nr. 2: pp. 243-246. Biologie

Subfractions isolated from intact purified spinach chloroplasts are able to prenylate the aromatic moiety of -tocopherol and plastoquinone-9 precursors. The biosynthesis of -tocopherol and plastoquinone-9 is a compartmentalized process. The chloroplast envelope membranes are the only site of the enzymatic prenylation in -tocopherol synthesis whereas the thylakoid membrane is also involved in the prenylation and methylation sequence of plastoquinone-9 biosynthesis. A very active kinase which forms phytyl-PP is localized in the stroma. Phytol but not geranylgeraniol is the polyprenol precursor of the side chain of -tocopherol in spinach chloroplasts.

Geranylgeranyl substituted methylquinols are shown to be precursors of tocopherol biosynthesis in spinach chloroplasts as well as phytyl substituted ones. The geranylgeranyl substituted quinols are methylated even to a greater extent than the phytyl substituted ones. The connection to the so far known biosynthetic origin of -tocopherol is probably -tocotrienol which is hydrogenated to γ-tocopherol and then further methylated to -tocopherol.