PubMed · 2026-02-20
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.
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.
