Brassinosteroid signaling directs formative cell divisions and protophloem differentiation in Arabidopsis root meristems

• DOI: 10.1242/dev.145623
• Publication Date: 2017-01-17T12:41:58Z
• Authors: Yeon Hee Kang; Alice Breda; Christian S. Hardtke
• Keywords: Brassinosteroid; Cell fate determination

ABSTRACT Brassinosteroids (BRs) trigger an intracellular signaling cascade through its receptors BR INSENSITIVE 1 (BRI1), BRI1-LIKE (BRL1) and BRL3. Recent studies suggest that BR-independent inputs related to vascular differentiation, for instance root protophloem development, modulate downstream components. Here, we report sieve element differentiation is indeed impaired in bri1 brl1 brl3 mutants, although this effect might not be mediated by canonical We also found their small meristem size entirely explained reduced cell elongation, which is, however, accompanied supernumerary formative divisions the radial dimension. Thus, expansion conjunction with growth retardation, because of need accommodate divisions, can account overall short phenotype mutants. Tissue-specific re-addition BRI1 activity partially rescued subsets these defects partly cell-autonomous, non-cell-autonomous effects. However, protophloem-specific expression essentially all major phenotypes. Our data perception sufficient systemically convey action context.