A conserved fungal effector disturbs Ca2+ sensing and ROS homeostasis to induce plant cell death
Yunlong Lin, Chan Xu, Lili Li, Liqin Fan, Rui Li, Jiaxin He, Hongli Li, Wei Deng, Zhensheng Kang, Zhengguo Li, Yulin Cheng
Abstract
Acting as a major Ca2+ sensor, calmodulin (CaM) activates target proteins to regulate a variety of cellular processes. Here, we report that CaM–target binding is disturbed by a fungal virulence effector PdCDIE1 (Penicillium digitatum Cell Death-Inducing Effector 1), which results into reactive oxygen species (ROS)-dependent plant cell death. PdCDIE1 is an evolutionarily conserved fungal effector that exhibits plant cell death-inducing activity and contributes significantly to pathogen virulence. PdCDIE1 interacts with a plant heat shock protein Hsp70 that is antagonistic to ROS-dependent plant cell death. Hsp70 is a bona fide target of CaM and its CaM-binding domain also interacts with N-terminal PdCDIE1. The interaction between CaM and Hsp70 in citrus fruit is disturbed during pathogen infection but recovered during ΔPdCDIE1 mutant infection. Application of a CaM inhibitor and silencing of CaM genes induce plant cell death and high levels of ROS as PdCDIE1 does. These results reveal a molecular framework of effector-triggered susceptibility which integrates Ca2+ sensing and ROS homeostasis to induce plant cell death. Calmodulin (CaM) activates target proteins to regulate a variety of cellular processes. Here, the authors report that CaM–target binding is disturbed by a fungal effector PdCDIE1, leading to ROS-dependent plant cell death.