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Time for a thread!🧵 How different is the molecular organization of thylakoids in “higher” plants🌱? To find out, we teamed up with @profmattjohnson.bsky.social to dive into spinach chloroplasts with #CryoET ❄️🔬. Curious? ..Read on! #TeamTomo #PlantScience 🧪 🧶🧬 🌾 elifesciences.org/articles/105... 1/🧵

Unlike in algae and other phototrophs, plant thylakoids form specialized grana stacks🥞 interconnected by single thylakoids called stromal lamellae. The 3D membrane architecture we observed is consistent with the “helical staircase model” proposed from classical TEM (💚🔬 Andrew Staehelin, RIP). 2/🧵

We made an interesting observation about plastoglobules, lipid-protein storage droplets that share one leaflet with thylakoid membranes. We saw that plastoglobules often sat within little holes in the thylakoids 🟠🕳️, perhaps increasing the area of the contact site, facilitating exchange 🔄 3/🧵

Our data enabled us to quantify native thylakoid architecture in the grana. Getting precise numbers is important for modeling photosynthetic regulation. Here’s a comparison to similar measurements made by classical TEM. We’d like to apply #CryoET to the dark-to-light💡 transition in the future. 4/🧵

The talented @lorenzlamm.bsky.social (joint PhD w/ @tingyingpeng.bsky.social) developed #MemBrain 🤖🧠software to automatically segment the thylakoid membranes and localize all the photosystem II (PSII) complexes embedded within them. Let’s get analyzing!👨‍💻🤓 Try MemBrain: bsky.app/profile/lore... 6/🧵

For decades, the idea has persisted that grana margins have a distinct protein composition and provide a zone where PSI & PSII can intermix. However, our "membranograms" revealed strict lateral heterogeneity between PSI & PSII at the margins, just like we previously observed in green algae 🟦🟨 7/🧵

We also observed that PSII concentration was uniform throughout each granum, irrespective of distance from the margin. Thus, we propose a simple two-domain model of thylakoid organization in green algae and plants. And yes, we speculate about domain #PhaseSeparation. I await your hate mail 📬🤗 8/🧵