RACK1 links phyB and BES1 to coordinate brassinosteroid‐dependent root meristem development

• Published in: The New phytologist Vol. 244; no. 3; pp. 883 - 899
• Main Authors: Zhu, Wei, Fu, Yajuan, Zhou, Hua, Zhou, Yeling, Zhang, Dayan, Wang, Yuzhu, Su, Yujing, Li, Zhiyong, Liang, Jiansheng
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.11.2024
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; brassinosteroid signaling; Brassinosteroids; Brassinosteroids - metabolism; Cell division; Cyclins - genetics; DNA-Binding Proteins - metabolism; Gene regulation; Light; light signaling; Meristem - growth & development; Meristem - metabolism; Meristems; Photoreceptors; phyB; Phytochrome B; Phytochrome B - metabolism; Plant growth; Plant growth substances; Plant Roots - growth & development; Plant Roots - metabolism; Promoter Regions, Genetic; Protein Kinases - metabolism; Proteins; RACK1; Receptors for Activated C Kinase - metabolism; root meristem; scaffold protein; Scaffolds; Soil; RACK1; scaffold protein; light signaling; brassinosteroid signaling; phyB; root meristem
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.20055

Summary 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.