Genetic Evidence for an Indispensable Role of Somatic Embryogenesis Receptor Kinases in Brassinosteroid Signaling

• DOI: 10.1371/journal.pgen.1002452
• Publication Date: 2012-01-12T22:08:34Z
• Authors: Xiaoping Gou; Hongju Yin; Kai He; Junbo Du; Jing Yi; Shengbao Xu; Honghui Lin; Steven D. Clouse; Jia Li
• Keywords: Brassinosteroid; Wild type

The Arabidopsis thaliana somatic embryogenesis receptor kinases (SERKs) consist of five members, SERK1 to SERK5, the leucine-rich repeat receptor-like kinase subfamily II (LRR-RLK II). SERK3 was named BRI1-Associated Receptor Kinase 1 (BAK1) due its direct interaction with brassinosteroid (BR) BRI1 in vivo, while SERK4 has also been designated as BAK1-Like (BKK1) for functionally redundant role BAK1. Here we provide genetic and biochemical evidence demonstrate that SERKs are absolutely required early steps BR signaling. Overexpression four SERKs-SERK1, SERK2, SERK3/BAK1, SERK4/BKK1-suppressed phenotypes an intermediate mutant, bri1-5. kinase-dead versions these genes bri1-5 background, on other hand, resulted typical dominant negative phenotypes, resembling those null mutants. We isolated generated single, double, triple, quadruple mutants analyzed their detail. While mutant is embryo-lethal, serk1 bak1 bkk1 triple exhibits extreme de-etiolated phenotype similar a bri1 mutant. overexpression can drastically increase hypocotyl growth wild-type plants, does not alter Biochemical analysis indicated phosphorylation level incapable sensing exogenously applied BR. As result, unphosphorylated BES1 lost sensitivity treatment indicating signaling pathway completely abolished These data clearly essential events