Nicotiana benthamina MAPK-WRKY pathway regulates effector-triggered ROS burst to confer resistance against Phytophthora infestans
H. ADACHI (1), T. Nakano (2), N. Miyagawa (3), N. Ishihama (4), M. Yoshioka (2), Y. Katou (2), T. Yaeno (5), K. Shirasu (4), H. Yoshioka (2) (1) Graduate School of Bioagricultural Sciences, Nagoya University, Japan; (2) Graduate School of Bioagricultural Sciences, Nagoya University, Japan; (3) ZEN-NOH, Japan; (4) RIKEN CSRS, Japan; (5) Faculty of Agriculture, Ehime University, Japan

A plant NADPH oxidase, RBOH is regulated at the transcriptional and post-translational levels to generate ROS for plant immunity. However, the regulatory mechanism of RBOH gene and its role in pathogen-responsive ROS burst are unclear. In Nicotiana benthamiana, activation of MEK2 cascade, one of the tobacco MAPK cascades, induces ROS production mediated by NbRBOHB, which is required for ROS burst against oomycete pathogen Phytophthora infestans. NbRBOHB expression is significantly up-regulated in response to constitutively active MEK2 (MEK2DD) and potato R protein/oomycete effector pair (R3a/AVR3a), but modest to a bacterial molecular pattern (flg22). We identified a cis-element, which is essential for MEK2DD- and R3a/AVR3a-triggered activation of NbRBOHB promoter. Moreover, we isolated WRKY transcription factors for the cis-element-mediated NbRBOHB transactivation. Yeast one-hybrid and chromatin immunoprecipitation assays showed direct binding of the WRKY to the cis-element in yeasts and in plants. Loss-of-function analyses showed that MEK2DD- and R3a/AVR3a-triggered ROS bursts and NbRBOHB transactivation were compromised in WRKY gene-silenced plants. Furthermore, the WRKY gene silencing suppressed cell death induction against P. infestans, resulting in the growth of P. infestans. These findings suggest that MAPK-WRKY pathway transactivates NbRBOHB for effector-triggered ROS burst and confers cell death-mediated resistance to P. infestans.

Abstract Number: P18-657
Session Type: Poster