Cryptochrome 1 (CRY1) is an important light receptor essential for de-etiolation of Arabidopsis seedlings. However, its function in regulating plant architecture remains unclear. Here, we show that mutation in CRY1 resulted in increased branching of Arabidopsis plants. To investigate the underlying mechanism, we analyzed the expression profiles of branching-related genes and found that the mRNA levels of Phytochrome Interaction Factor 4 (PIF4) and PIF5 are significantly increased in the cry1 mutant. Genetic analysis showed that the pif4 or pif4pif5 mutant is epistatic to the cry1 mutant, and overexpression of PIF4 conferred increased branching. Moreover, we demonstrated that PIF4 proteins physically associate with the G-box motif within the PIF4 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.

隐花色素 1 (CRY1) 是一种重要的光受体，对拟南芥幼苗的去黄化至关重要。然而，其在调节植物结构方面的功能仍不清楚。在这里，我们表明CRY1中的突变导致拟南芥植物的分枝增加。为了研究潜在的机制，我们分析了分支相关基因的表达谱，发现光敏色素相互作用因子 4 ( PIF4 ) 和PIF5的 mRNA 水平在cry1突变体中显着增加。遗传分析表明，pif4或pif4pif5突变体对cry1是上位性的突变体，而PIF4 的过表达导致分支增加。此外，我们证明了 PIF4 蛋白与PIF4启动子内的 G-box 基序物理结合以形成自激活的转录反馈回路，而 CRY1 抑制这一过程以响应蓝光。总之，这项研究表明 CRY1-PIF4 模块通过形成调节环和枝条分支来调节基因表达以响应环境光条件。