BRL1 and BRL3 are novel brassinosteroid receptors that function in vascular differentiation in Arabidopsis.
Plant steroid hormones, brassinosteroids (BRs), are perceived by the plasma membrane-localized leucine-rich-repeat-receptor kinase BRI1. Based on sequence similarity, we have identified three members of the BRI1 family, named BRL1, BRL2 and BRL3. BRL1 and BRL3, but not BRL2, encode functional BR receptors that bind brassinolide, the most active BR, with high affinity. In agreement, only BRL1 and BRL3 can rescue bri1 mutants when expressed under the control of the BRI1 promoter. While BRI1 is ubiquitously expressed in growing cells, the expression of BRL1 and BRL3 is restricted to non-overlapping subsets of vascular cells. Loss-of-function of brl1 causes abnormal phloem:xylem differentiation ratios and enhances the vascular defects of a weak bri1 mutant. bri1 brl1 brl3 triple mutants enhance bri1 dwarfism and also exhibit abnormal vascular differentiation. Thus, Arabidopsis contains a small number of BR receptors that have specific functions in cell growth and vascular differentiation.
Howard Hughes Medical Institute and Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA.
Ana
A
Caño-Delgado
Yanhai
Y
Yin
Cong
C
Yu
Dionne
D
Vafeados
Santiago
S
Mora-García
Jin-Chen
JC
Cheng
Kyoung Hee
KH
Nam
Jianming
J
Li
Joanne
J
Chory
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids; D002454:Cell Differentiation; D002777:Cholestanols / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017385:Sequence Homology; D013260:Steroids, Heterocyclic / Q000378:metabolism
D029681:Arabidopsis Proteins; C494334:BRL1 protein, Arabidopsis; C494335:BRL3 protein, Arabidopsis; D060406:Brassinosteroids; D002777:Cholestanols; D011956:Receptors, Cell Surface; D013260:Steroids, Heterocyclic; C023623:brassinolide