Plant Biology
The Variable Domain of a Plant Calcium-dependent Protein Kinase (CDPK) Confers Subcellular Localization and Substrate Recognition for NADPH Oxidase*

https://doi.org/10.1074/jbc.M112.448910Get rights and content
Under a Creative Commons license
open access

Calcium-dependent protein kinases (CDPKs) are Ca2+ sensors that regulate diverse biological processes in plants and apicomplexans. However, how CDPKs discriminate specific substrates in vivo is still largely unknown. Previously, we found that a potato StCDPK5 is dominantly localized to the plasma membrane and activates the plasma membrane NADPH oxidase (RBOH; for respiratory burst oxidase homolog) StRBOHB by direct phosphorylation of the N-terminal region. Here, we report the contribution of the StCDPK5 N-terminal variable (V) domain to activation of StRBOHB in vivo using heterologous expression system in Nicotiana benthamiana. Mutations of N-terminal myristoylation and palmitoylation sites in the V domain eliminated the predominantly plasma membrane localization and the capacity of StCDPK5 to activate StRBOHB in vivo. A tomato SlCDPK2, which also contains myristoylation and palmitoylation sites in its N terminus, phosphorylated StRBOHB in vitro but not in vivo. Functional domains responsible for activation and phosphorylation of StRBOHB were identified by swapping regions for each domain between StCDPK5 and SlCDPK2. The substitution of the V domain of StCDPK5 with that of SlCDPK2 abolished the activation and phosphorylation abilities of StRBOHB in vivo and relocalized the chimeric CDPK to the trans-Golgi network, as observed for SlCDPK2. Conversely, SlCDPK2 substituted with the V domain of StCDPK5 localized to the plasma membrane and activated StRBOHB. These results suggest that the V domains confer substrate specificity in vivo by dictating proper subcellular localization of CDPKs.

NADPH Oxidase
Phosphorylation
Plant Defense
Reactive Oxygen Species (ROS)
Signal Transduction
Calcium-dependent Protein Kinase
Plant Immunity

Cited by (0)

*

This work was supported by a Grant-in-aid for Scientific Research on Innovative Areas 23117707 from the Ministry of Education, Science, and Culture, Sports, Science, and Technology of Japan (to H. Y.), a research fellowship from the Japan Society for the Promotion of Science (to S.A.), 23580068 (to Y. K.), the Excellent Young Researcher Overseas Visit Program (to Y.K.), the Uehara memorial foundation (to Y.K), and the Gatsby Charitable Foundation (to C. Z. and J. D. G. J.).