Brassinosteroid-regulated plant growth and development and gene expression in soybean

Brassinosteroids (BRs) are endogenous phytohormones that play important roles in regulating plant growth and development. In this study, we evaluated the effects of brassinolide (BL, one of the active BRs) on soybean and identified roles of the hormone in regulating multiple aspects of plant growth and development. BL application promoted hypocotyl and epicotyl elongation in the light but blocked epicotyl elongation in the dark. High levels of castasterone and BL accumulated in light-grown plants. BL disrupted shoot negative gravitropism, whereas gibberellin did not. BL delayed leaf senescence. Transcriptome analysis showed that BL induced cell wall-modifying genes and auxin-associated genes but suppressed a class of WRKY genes involved in senescence and stress responses, showing the complex roles of BRs in multiple biological processes.