Phytochromes A and B Mediate Light Stabilization of BIN2 to Regulate Brassinosteroid Signaling and Photomorphogenesis in Arabidopsis

Phytochromes A and B Mediate Light Stabilization of BIN2 to Regulate Brassinosteroid Signaling and Photomorphogenesis in Arabidopsis

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Phytochromes A and B (phyA and phyB) are the far-red and red lights photoreceptors mediating many light responses in Arabidopsis thaliana.Brassinosteroid read more (BR) is a pivotal phytohormone regulating a variety of plant developmental processes including photomorphogenesis.It is known that phyB interacts with BES1 to inhibit its DNA-binding activity and repress BR signaling.Here, we show that far-red and red lights modulate BR signaling through phyA and phyB regulation of the stability of BIN2, a glycogen synthase kinase 3 (GSK3)-like kinase that phosphorylates BES1/BZR1 to inhibit BR signaling.

The BIN2 gain-of-function mutant bin2-1 displays an enhanced photomorphogenic phenotype in both far-red and red lights.phyA-enhanced accumulation of BIN2 promotes the phosphorylation of BES1 in far-red light.BIN2 acts genetically downstream from 30x24x24 wall cabinet PHYA to regulate photomorphogenesis under far-red light.Both phyA and phyB interact directly with BIN2, which may promote the interaction of BIN2 with BES1 and induce the phosphorylation of BES1.

Our results suggest that far-red and red lights inhibit BR signaling through phyA and phyB stabilization of BIN2 and promotion of BES1 phosphorylation, which defines a new layer of the regulatory mechanism that allows plants to coordinate light and BR signaling pathways to optimize photomorphogenesis.