Brassinosteroid Sensing and Signaling in Plants
Brassinosteroids (BRs) are a class of growth-promoting steroid hormones in plants, which are sensed by the membrane receptor kinase BRASSINOSTEROID INSENSITIVE 1 (BRI1). BR binding to the extracellular domain of BRI1 creates a docking platform for shape-complementary co-receptor kinases of the SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) family. Ligand-induced hetero-dimerization of BRI1 with a SERK co-receptor at the cell surface renders their cytoplasmic kinase domains competent to trans-phosphorylate and activate each other. The fully active BRI1 kinase domain can then initiate a cytoplasmic signaling cascade, leading to substantial changes in gene expression. Here, we summarize our current mechanistic understanding of brassinosteroid sensing and BRI1 receptor activation.
Financial support by the Swiss National Science Foundation (grant number 156920) is gratefully acknowledged.
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