OsSERK1 regulates rice development but not immunity to Xanthomonas oryzae pv . oryzae or Magnaporthe oryzae

Somatic embryogenesis receptor kinase (SERK) proteins play pivotal roles in regulation of plant development and immunity. The rice genome contains two SERK genes, OsSerk1 and OsSerk2 . We previously demonstrated that OsSerk2 is required for rice Xa21 ‐mediated resistance to Xanthomonas oryzae pv. oryzae ( Xoo ) and for normal development. Here we report the molecular characterization of OsSerk1 . Overexpression of OsSerk1 results in a semi‐dwarf phenotype whereas silencing of OsSerk1 results in a reduced angle of the lamina joint. OsSerk1 is not required for rice resistance to Xoo or Magnaporthe oryzae . Overexpression of OsSerk1 in OsSerk2 ‐silenced lines complements phenotypes associated with brassinosteroid (BR) signaling defects, but not the disease resistance phenotype mediated by Xa21 . In yeast, OsSERK1 interacts with itself forming homodimers, and also interacts with the kinase domains of OsSERK2 and BRI1, respectively. OsSERK1 is a functional protein kinase capable of auto‐phosphorylation in vitro . We conclude that, whereas OsSERK2 regulates both rice development and immunity, OsSERK1 functions in rice development but not immunity to Xoo and M. oryzae .