Zhao Yuqing, Han Qing, Kang Xinke, Tan Wenrong, Yao Xiuhong, Zhang Yang, Shi Haoyu, Xia Ran, Wu Xuemei, Lin Honghui, Zhang Dawei
Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China.
School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China.
Plant Physiol. 2024 Dec 23;197(1). doi: 10.1093/plphys/kiae542.
Plants dynamically modulate their growth and development to acclimate to the fluctuating light environment via a complex phytohormone network. However, the dynamic molecular regulatory mechanisms underlying how plants regulate phytohormones during skotomorphogenesis and photomorphogenesis are largely unknown. Here, we identified a HD-ZIP II transcription factor, HOMEODOMAIN ARABIDOPSIS THALIANA1 (HAT1), as a key node that modulates the dose effects of brassinosteroids (BRs) and auxin on hypocotyl growth during skotomorphogenesis and photomorphogenesis. Compared with the wild-type (Col-0), both HAT1 loss of function and its overexpression led to disrupted photomorphogenic and skotomorphogenic hypocotyl growth. HAT1 overexpression (HAT1OX) plants displayed longer hypocotyls in the light but shorter hypocotyls in darkness, whereas the triple mutant hat1hat2hat3 showed the opposite phenotype. Furthermore, we found that CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) interacted with dephosphorylated HAT1 and facilitated the degradation of HAT1 by ubiquitination in darkness, while HAT1 was phosphorylated and stabilized by BRASSINOSTEROID INSENSITIVE2 (BIN2) in the light. Interestingly, we observed distinct dose-dependent effects of BR and auxin on hypocotyl elongation under varying light conditions and that HAT1 functioned as a key node in this process. The shorter hypocotyl of HAT1OX in darkness was due to the inhibition of BR biosynthetic gene BRASSINOSTEROID-6-OXIDASE2 (BR6OX2) expression to reduce BRs content, while brassinolide (BL) treatment alleviated this growth repression. In the light, HAT1 inhibited BR biosynthesis but enhanced auxin signaling by directly repressing IAA3/SHORT HYPOCOTYL 2 (SHY2) expression. Our findings uncover a dual function of HAT1 in regulating BR biosynthesis and auxin signaling that is crucial for ensuring proper skotomorphogenic and photomorphogenic growth.
植物通过复杂的植物激素网络动态调节其生长和发育，以适应波动的光照环境。然而，在暗形态建成和光形态建成过程中，植物如何调节植物激素的动态分子调控机制在很大程度上尚不清楚。在这里，我们鉴定了一个HD-ZIP II转录因子，拟南芥同源异型域1（HAT1），它是一个关键节点，在暗形态建成和光形态建成过程中调节油菜素内酯（BRs）和生长素对下胚轴生长的剂量效应。与野生型（Col-0）相比，HAT1功能丧失及其过表达均导致光形态建成和暗形态建成下胚轴生长紊乱。HAT1过表达（HAT1OX）植株在光照下下胚轴较长，而在黑暗中较短，而三突变体hat1hat2hat3表现出相反的表型。此外，我们发现组成型光形态建成1（COP1）与去磷酸化的HAT1相互作用，并在黑暗中通过泛素化促进HAT1的降解，而HAT1在光照下被油菜素内酯不敏感2（BIN2）磷酸化并稳定。有趣的是，我们观察到在不同光照条件下，BR和生长素对下胚轴伸长有明显的剂量依赖性效应，并且HAT1在此过程中起关键节点的作用。HAT1OX在黑暗中较短的下胚轴是由于BR生物合成基因油菜素内酯-6-氧化酶2（BR6OX2）表达受到抑制，从而降低了BRs含量，而油菜素内酯（BL）处理缓解了这种生长抑制。在光照下，HAT1抑制BR生物合成，但通过直接抑制IAA3/短下胚轴2（SHY2）表达增强生长素信号传导。我们的研究结果揭示了HAT1在调节BR生物合成和生长素信号传导中的双重功能，这对于确保适当的暗形态建成和光形态建成生长至关重要。
