Cucumber Mildew Resistance Locus O Interacts with Calmodulin and Regulates Plant Cell Death Associated with Plant Immunity.

Pathogen-induced cell death is closely related to plant disease susceptibility and resistance. The cucumber ( L.) mildew resistance locus O (CsMLO1) and calmodulin (CsCaM3) genes, as molecular components, are linked to nonhost resistance and hypersensitive cell death. In this study, we demonstrate that CsMLO1 interacts with CsCaM3 via yeast two-hybrid, firefly luciferase (LUC) complementation and bimolecular fluorescence complementation (BiFC) experiments. A subcellular localization analysis of green fluorescent protein (GFP) fusion reveals that is transferred from the cytoplasm to the plasma membrane in , and green fluorescence is significantly attenuated via the coexpression of and negatively regulates expression in transiently transformed cucumbers, and hypersensitive cell death is disrupted by and/or expression under infection. Additionally, silencing significantly enhances the expression of reactive oxygen species (ROS)-related genes (, , and ), defense marker genes ( and ) and callose deposition-related gene () in infected cucumbers. These results suggest that the interaction of CsMLO1 with CsCaM3 may act as a cell death regulator associated with plant immunity and disease.