Cryptochromes interact directly with PIFs to control plant growth in limiting blue light

Sun-loving plants have the ability to detect and avoid shading through sensing of both blue and red light wavelengths. Higher plant cryptochromes (CRYs) control how plants modulate growth in response to changes in blue light. For growth under a canopy, where blue light is diminished, CRY1 and CRY2 perceive this change and respond by directly contacting two bHLH transcription factors, PIF4 and PIF5. These factors are also known to be controlled by phytochromes, the red/far-red photoreceptors; however, transcriptome analyses indicate that the gene regulatory programs induced by the different light wavelengths are distinct. Our results indicate that CRYs signal by modulating PIF activity genome-wide, and that these factors integrate binding of different plant photoreceptors to facilitate growth changes under different light conditions. Overall design: We performed whole-genome transcriptome (mRNA-seq) analysis on 5-day-old Arabidopsis thaliana Columbia wild-type (WT) and pif4pif5 seedlings exposed to low blue-light (LBL) or mock-treated for 1, 6 and 24 hours. In addition we performed mRNA-seq on WT, 35S::PIF4-9xMyc-6x-His-3xFlag(Flash) and 35S::PIF5-9xMyc-6x-His-3xFlag (Flash) seedlings treated with LBL or mock-treated for 16 hours.

喜阳植物可通过感知蓝光与红光波长，检测并规避遮荫环境。高等植物的隐花色素（cryptochromes, CRYs）可调控植物响应蓝光变化的生长模式。在冠层遮蔽的生长环境中，蓝光水平会被显著削弱，此时CRY1与CRY2会感知这一变化，并通过直接结合两种碱性螺旋-环-螺旋（basic helix-loop-helix, bHLH）转录因子PIF4与PIF5做出应答。已知这两类转录因子同时受红光/远红光光受体光敏色素（phytochromes）调控；但转录组分析结果显示，不同光波长所诱导的基因调控程序存在显著差异。本研究结果表明，CRYs通过在全基因组层面调控PIF家族的活性完成信号转导，且这些转录因子能够整合不同植物光受体的结合信号，从而助力植物在不同光照条件下实现生长调控。实验总体设计：我们对暴露于低蓝光（low blue-light, LBL）环境或经假处理的5日龄拟南芥（Arabidopsis thaliana）哥伦比亚生态型野生型（WT）与pif4pif5双突变幼苗，分别开展1小时、6小时及24小时的全基因组转录组mRNA测序（mRNA-seq）分析。此外，我们还对经LBL处理或假处理16小时的野生型、35S::PIF4-9xMyc-6x-His-3xFlag(Flash)及35S::PIF5-9xMyc-6x-His-3xFlag(Flash)幼苗进行了mRNA-seq分析。