Reversible phosphorylation of NPH3/RPT2-like proteins regulates phototropin receptor signaling.
Sullivan S, Hermanowicz P, Higa T, Waksman T, Gotoh E
Plant Signaling
Understanding how plants optimize their response to light could lead to crop varieties that capture sunlight more efficiently — meaning better yields even in shaded fields or under variable weather conditions.
Plants have proteins that act like traffic signals, telling them which way to grow toward light and how to position their internal solar panels (chloroplasts). Scientists discovered a pair of molecular 'reset buttons' — enzymes called PP2C19 and PP2C35 — that turn off a chemical tag on one of these traffic signal proteins so the whole system can recharge and work again. Without these reset buttons, plants get stuck and can't properly bend toward light or move their chloroplasts into the best position for absorbing sunlight.
Key Findings
Two phosphatase enzymes (PP2C19 and PP2C35) act redundantly to remove a phosphate group from the NPH3 protein at position S744, resetting the light-response signaling complex at the cell membrane.
Plants lacking both PP2C19 and PP2C35 show significantly reduced phototropism (bending toward light) and impaired chloroplast repositioning — defects seen in both Arabidopsis (thale cress) and Marchantia (a liverwort), suggesting this mechanism is ancient and conserved.
These same phosphatases also regulate two other light-response proteins (RPT2 and NCH1), indicating they serve as broad master regulators of multiple phototropin-dependent light responses including gravitropism.
chevron_right Technical Summary
Scientists identified the molecular 'off switch' that resets a key plant light-sensing system, allowing plants to continuously track and respond to light. This discovery explains how plants fine-tune their ability to bend toward light and position their chloroplasts for optimal photosynthesis.
Abstract Preview
Phototropin receptor kinases (phot1 and phot2) enhance photosynthesis by coordinating light responses such as phototropism and chloroplast repositioning under low blue light conditions. These proce...
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