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Abstract：
Light and temperature, in coordination with the endogenous clock and the hormones gibberellin (GA) and brassinosteroids (BRs), modulate plant growth and development by affecting the expression of multiple cell wall- and auxin-related genes. PHYTOCHROME INTERACTING FACTORS (PIFs) play a central role in the activation of these genes, the activity of these factors being regulated by the circadian clock and phytochrome-mediated protein destabilization. GA signaling is also integrated at the level of PIFs; the DELLA repressors are found to bind these factors and impair their DNA-binding ability. The recent finding that PIFs are co-activated by BES1 and BZR1 highlights a further role of these regulators in BR signal integration, and reveals that PIFs act in a concerted manner with the BR-related BES1/BZR1 factors to activate auxin synthesis and transport at the gene expression level, and synergistically activate several genes with a role in cell expansion. Auxins feed back into this growth regulatory module by inducing GA biosynthesis and BES1/BZR1 gene expression, in addition to directly regulating several of these growth pathway gene targets. An exciting challenge in the future will be to understand how this growth program is dynamically regulated in time and space to orchestrate differential organ expansion and to provide plants with adaptation flexibility.
摘要：
光和温度，与内源性生物钟和激素赤霉素（GA）和油菜素类固醇（BRs）协调，通过影响多个细胞壁和生长素相关基因的表达来调节植物的生长和发育。植物铬相互作用因子（PIFs）在这些基因的激活中起着核心作用，这些因子的活性受到生物钟和植物色素介导的蛋白质不稳定的调节。GA信号也在PIF水平上整合;发现DELLA阻遏物结合这些因子并削弱其DNA结合能力。最近发现PIF被BES1和BZR1共同激活，突出了这些调节器在BR信号积分中的进一步作用。并揭示了PIFs与BR相关的BES1/BZR1因子协同作用，在基因表达水平上激活生长素的合成和转运，并协同激活几个在细胞扩增中起作用的基因。生长素通过诱导GA生物合成和BES1/BZR1基因表达反馈到该生长调节模块中，除了直接调控这些生长途径基因的几个靶点。未来一个令人兴奋的挑战将是了解这种生长计划如何在时间和空间上动态调节，以协调不同的器官扩张并为植物提供适应灵活性。
