Differential requirement of BAK1 C-terminal tail in development and immunity.

BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) plays critical roles in plant developmental and immune signaling pathways. BAK1 and a large number of leucine-rich repeat receptor-like kinases (LRR-RLKs) harbor a mysterious carboxyl-terminal tail (CT) beyond their kinase domain. In this study we analyzed the biological significance of this CT region using a unique bak1 mutant allele which causes deletion of the CT region. We showed that BAK1 CT promotes its kinase activity and is required for pathogen-associated molecular pattern (PAMP)-triggered immunity, but it is dispensable for brassinosteroid responses and BAK1/BKK1-inhibited cell death signaling. Therefore the BAK1 C-terminal tail is differentially required for its functions in development and immunity.