The Arabidopsis PIF4 and BES1/BZR1 transcription factors antagonize light signaling by facilitating co‐activated expression of a large number of cell wall‐loosening and auxin‐related genes. While PIF4 directly activates expression of these targets, BES1 and BZR1 activity switch from a repressive to an activator function, depending on interaction with TOPLESS and other families of regulators including PIFs. However, the complexity of this regulation and its role in diurnal control of plant growth and brassinosteroid (BR) levels is little understood. We show by using a protein array that BES1, PIF4, and the BES1‐PIF4 complex recognize different DNA elements, thus revealing a distinctive cis‐regulatory code beneath BES1‐repressive and PIF4 co‐activation function. BES1 homodimers bind to conserved BRRE‐ and G‐box elements in the BR biosynthetic promoters and inhibit their expression during the day, while elevated PIF4 competes for BES1 homodimer formation, resulting in de‐repressed BR biosynthesis at dawn and in response to warmth. Our findings demonstrate a central role of PIF4 in BR synthesis activation, increased BR levels being essential to thermomorphogenic hypocotyl growth.

的拟南芥PIF 4和BES 1 / BZR 1转录因子通过促进大量细胞壁松动和生长素相关基因的共激活表达拮抗光信令。虽然PIF 4直接激活这些靶标的表达，但BES 1和BZR 1的活性从抑制功能转变为激活功能，这取决于与TOPLESS和其他调节剂家族（包括PIF）的相互作用。但是，对该法规的复杂性及其在昼夜控制植物生长和油菜素内酯（BR）水平中的作用知之甚少。我们通过使用蛋白质阵列证明BES 1，PIF 4和BES 1至PIF 4复合体识别不同的DNA元素，因此在BES 1抑制和PIF 4共激活功能下揭示了独特的顺式调控密码。BES 1同型二聚体与BR生物合成启动子中保守的BRRE-和G-box元素结合并在白天抑制其表达，而升高的PIF 4竞争BES 1同型二聚体的形成，导致黎明时分和响应于BR的BR生物合成受到抑制。温暖。我们的发现证明了PIF 4在BR中的核心作用合成激活，增加BR水平是热形态发生下胚轴生长必不可少的。