Disruption of MoCMK1, encoding a putative calcium/calmodulin-dependent kinase, in Magnaporthe oryzae

SummaryCa2+ is a second messenger in pathways that transduce external signals and activate cellular processes in plants and animals. Ca2+-mediated signal transduction is involved in key pathways that contribute to a variety of fundamental physiological processes in eukaryotic cells. However, little is known about the molecular mechanisms of Ca2+-mediated signal transduction in filamentous fungi. In this study, the MoCMK1 gene, encoding a putative Ca2+/calmodulin-dependent kinase, was identified in the rice blast fungus Magnaporthe oryzae. Three MoCMK1 deletion mutants were obtained by a targeted gene replacement. Colonies of the MoCMK1 mutants had sparse aerial hyphae and fewer conidia than the wild-type strain on complete medium. Conidial germination and appressorial formation were delayed in the ΔMocmk1 mutants. In spray inoculation tests, ΔMocmk1 mutants exhibited a weakened ability to infect the susceptible rice cultivar CO-39, compared to the wild-type strain Guy11. These results showed that MoCMK1 plays key roles in the pathogenicity of the rice blast fungus.