PHOTOPERIODIC CONTROL OF HYPOCOTYL 1 (PCH1) and PCH1-LIKE (PCHL) were shown to directly bind to phytochrome B (phyB) and suppress phyB thermal reversion, resulting in plants with dramatically enhanced light sensitivity. Here, we show that PCH1 and PCHL also positively regulate various light responses, including seed germination, hypocotyl gravitropism, and chlorophyll biosynthesis, by physically interacting with PHYTOCHROME INTERACTING FACTOR 1 (PIF1) and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). PCH1 and PCHL interact with PIF1 both in the dark and light, and regulate PIF1 abundance. Moreover, PCH1 and PCHL facilitate the physical interaction between phyB and PIF1 in vivo to promote the light-induced degradation of PIF1. PCH1 and PCHL also inhibit the DNA-binding ability of PIF1 to negatively regulate the expressions of PIF1 target genes. In addition, PCH1 and PCHL interact with COP1 and undergo degradation through the 26S proteasome pathway in the dark. Consistently, pch1 suppresses cop1 phenotype in darkness. Collectively, our study reveals a novel mechanism by which PCH1 and PCHL regulate diverse light responses not only by stabilizing phyB Pfr form but also by directly interacting with PIF1 and COP1, providing a molecular understanding of the control of hypocotyl growth by these proteins.

hypocotyl 1（PCH1）和PCH1-Like（PCHL）的光生态控制显示直接结合到植物色素B（phyB）并抑制phyB热回复，从而使植物的光敏性大大提高。在这里，我们显示PCH1和PCHL还通过与植物染色体相互作用因子1（PIF1）和本构性光致发光1（COP1）进行物理相互作用，还积极调节各种光响应，包括种子萌发，下胚轴重力和叶绿素生物合成。PCH1和PCHL在黑暗和明亮的情况下均与PIF1相互作用，并调节PIF1的丰度。此外，PCH1和PCHL促进了phyB和PIF1在体内的物理相互作用促进光诱导的PIF1降解。PCH1和PCHL还抑制PIF1的DNA结合能力，从而负面调节PIF1靶基因的表达。此外，PCH1和PCHL与COP1相互作用，并在黑暗中通过26S蛋白酶体途径降解。一致地，pch1在黑暗中抑制cop1表型。总的来说，我们的研究揭示了一种新的机制，通过该机制，PCH1和PCHL不仅可以稳定phyB Pfr形式，还可以通过直接与PIF1和COP1相互作用来调节多种光响应，从而提供了对这些蛋白质控制下胚轴生长的分子理解。