Shenzhen Key Laboratory of Plant Genetic Engineering and Molecular Design, Department of Biology, School of Life Sciences, Institute of Plant and Food Science, Southern University of Science and Technology, Shenzhen, 518055, China.
New Phytol. 2024 Nov;244(3):883-899. doi: 10.1111/nph.20055. Epub 2024 Aug 16.
Light and brassinosteroids (BR) are indispensable for plant growth and control cell division in the apical meristem. However, how external light signals cooperate with internal brassinosteroids to program root meristem development remains elusive. We reveal that the photoreceptor phytochrome B (phyB) guides the scaffold protein RACK1 to coordinate BR signaling for maintaining root meristematic activity. phyB and RACK1 promote early root meristem development. Mechanistically, RACK1 could reinforce the phyB-SPA1 association by interacting with both phyB and SPA1, which indirectly affects COP1-dependent RACK1 degradation, resulting in the accumulation of RACK1 in roots. Subsequently, RACK1 interacts with BES1 to repress its DNA-binding activity toward the target gene CYCD3;1, leading to the release of BES1-mediated inhibition of CYCD3;1 transcription, and hence the promotion of root meristem development. Our study provides mechanistic insights into the regulation of root meristem development by combination of light and phytohormones signals through the photoreceptors and scaffold proteins.
光是植物生长所必需的，并且在顶端分生组织中控制细胞分裂。然而，外部光信号如何与内部油菜素内酯协同作用来规划根分生组织的发育仍然难以捉摸。我们揭示了光受体光敏色素 B（phyB）指导支架蛋白 RACK1 协调油菜素内酯信号以维持根分生组织活性。phyB 和 RACK1 促进早期根分生组织的发育。在机制上，RACK1 可以通过与 phyB 和 SPA1 相互作用来增强 phyB-SPA1 复合物的形成，这间接影响 COP1 依赖性 RACK1 降解，导致 RACK1 在根中积累。随后，RACK1 与 BES1 相互作用，抑制其对靶基因 CYCD3;1 的 DNA 结合活性，从而解除 BES1 对 CYCD3;1 转录的抑制作用，进而促进根分生组织的发育。我们的研究提供了通过光受体和支架蛋白结合光和植物激素信号来调节根分生组织发育的机制见解。
