Cryptochrome 1 Inhibits Shoot Branching by Repressing the Self-Activated Transciption Loop of PIF4 in .

Cryptochrome 1 (CRY1) is an important light receptor essential for de-etiolation of seedlings. However, its function in regulating plant architecture remains unclear. Here, we show that mutation in resulted in increased branching of . To investigate the underlying mechanism, we analyzed the expression profiles of branching-related genes and found that the mRNA levels of () and are significantly increased in the mutant. Genetic analysis showed that the or mutant is epistatic to the mutant, and overexpression of conferred increased branching. Moreover, we demonstrated that PIF4 proteins physically associate with the G-box motif within the promoter to form a self-activated transcriptional feedback loop, while CRY1 represses this process in response to blue light. Taken together, this study suggests that the CRY1-PIF4 module regulates gene expression via forming a regulatory loop and shoot branching in response to ambient light conditions.