Light Modulates the Gravitropic Responses Through Organ-Specific PIFs and HY5 Regulation of LAZY4 Expression in Arabidopsis.

Significance Light and gravity are two key environmental factors that coordinately regulate plant gravitropism, but the underlying molecular mechanisms that drive this regulation are poorly understood. Here, we reveal that light represses expression of LAZY4 , a positive regulator of gravitropism, by promoting degradation of PIF proteins to inhibit negative gravitropism of hypocotyls in Arabidopsis . Meanwhile, light induces LAZY4 expression by promoting HY5 accumulation to enhance positive gravitropism in roots. Our findings provide key insights regarding the mechanism by which light mediates organ-specific gravitropism in plants.