Abstract:
Brassinosteroid (BR) plays a complex role in root growth and development by regulating the expression of downstream target genes through the BR signaling pathway. In this scRNA-seq study of Arabidopsis roots, tissue- and developmental-specific roles of BR were identified. Atrichoblast, an epidermal cell that develops into a non-hair cell, displayed the highest enrichment of BR-induced genes in the elongation and maturation zones among all cell types. Trajectory analysis revealed distinct expression patterns of BR biosynthesis and signaling genes between atrichoblasts and trichoblasts. Atrichoblasts exhibited higher expression levels of BR biosynthesis genes (DET2 and ROT3) and BR signaling genes (BRI1 and BSK1) during elongation and maturation stages compared to trichoblasts. This suggests that the higher levels of BR and BR signaling activity in atrichoblasts likely contribute to their larger percentages of BR-induced gene expression. Gene ontology analysis further revealed differences in BR-responsive gene sets related to cell wall processes between the two cell types. Specifically, EXTs that are BR-repressed genes showed specific expression in trichoblasts at the maturation stage, while XTHs that are BR-induced genes displayed higher expression in atrichoblasts during the elongation and maturation stages. Additionally, the validation of candidate genes on additional single-cell datasets supported the consistency of the findings and highlighted the significance of specific cell wall-related genes in determining atrichoblast fate.
