Yu Du, Xiaokang Chen, Yalu Guo, Xiaojiang Zhang, Houxiao Zhang, Fangfang Li, Guiyan Huang, Yuling Meng, Weixing Shan.Phytophthora infestans RXLR effector PITG20303 targets a potato MKK1 protein to suppress plant immunity

Phytophthora infestans RXLR effector PITG20303 targets a potato MKK1 protein to suppress plant immunity

Yu Du, Xiaokang Chen, Yalu Guo, Xiaojiang Zhang, Houxiao Zhang, Fangfang Li, Guiyan Huang, Yuling Meng, Weixing Shan

New Phytologist

DOI:10.1111/nph.16861

Abstract

·Pathogens secret a plethora of effectors into the host cell to modulate plant immunity. Analysing the role of effectors in altering the function of their host target proteins will reveal critical components of the plant immune system. ·Here we show that Phytophthora infestans RXLR effector PITG20303, a virulent variant of AVRblb2 (PITG20300) that escapes the recognition by the resistance protein Rpi-blb2, suppresses PAMP-triggered immunity (PTI) and promotes pathogen colonization by targeting and stabilizing a potato MAPK cascade protein, StMKK1. Both PITG20300 and PITG20303 target StMKK1, as confirmed by multiple in vivo and in vitro assays, and StMKK1 was shown as a negative regulator of plant immunity as determined by overexpression and gene silencing. ·StMKK1 is a negative regulator of plant PTI, and the kinase activities of StMKK1 is required for its suppression of PTI and effector interaction. PITG20303 partially depends on MKK1, PITG20300 does not depend on MKK1 for suppression of PTI-induced ROS burst, while the full virulence activities of nuclear targeted PITG20303 and PITG20300 are dependent on MKK1. ·Our results show that PITG20303 and PITG20300 target and stabilize the plant MAPK cascade signalling protein StMKK1 to negatively regulate plant PTI response.