One plant enzyme physically bridges photosynthesis and starch storage
Hwang SK, Tian L, Ng CY, Okita TW
Plant Signaling
Every leaf in your garden is quietly running a handoff between capturing sunlight and banking that energy as starch, and this study shows one enzyme literally holds both systems together in a single protein cluster.
Plants make sugar from sunlight and store extra energy as starch, and scientists used to think of these as separate jobs handled by separate teams of proteins. This research shows that one enzyme, starch phosphorylase, physically grabs onto parts of both teams, connecting the light-capturing machinery to the starch-making machinery like a molecular handshake. That link helps explain how a plant knows when to store energy versus when to use it right away.
Key Findings
Starch phosphorylase (Pho1) directly binds PsaC and PsaD, two subunits of photosystem I, but not a third subunit (PsaE), confirmed via yeast two-hybrid assays.
Pulldown assays across wild-type, BMF136, and Pho1-null plant lines show Pho1 is required to form a multi-protein complex containing PsaC and the starch-disproportionating enzyme Dpe1.
Pho1 variants lacking catalytic activity bound PsaC poorly, but adding a HaloTag to PsaC restored the interaction, suggesting the enzyme's structure helps stabilize the complex.
chevron_right Technical Summary
Scientists found that a plant enzyme called starch phosphorylase acts like a molecular hub, physically linking the machinery that makes starch to the machinery that captures light energy. This means plants may directly coordinate photosynthesis and energy storage through a shared protein complex rather than two separate processes.
Abstract Preview
Original paper
Starch phosphorylase acts as a pivotal scaffold connecting starch metabolism enzymes with photosystem I subunits.
In a previous study, we proposed that starch phosphorylase (Pho1) interacts with PsaC, a core subunit of photosystem I (PSI), although it was not clear whether the interaction was a direct 1:1 rela...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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