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A chemical genetic approach demonstrates that MPK 3/ MPK 6 activation and NADPH oxidase‐mediated oxidative burst are two independent signaling events in plant immunity
Author(s) -
Xu Juan,
Xie Jie,
Yan Chengfei,
Zou Xiaoqin,
Ren Dongtao,
Zhang Shuqun
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12382
Subject(s) - arabidopsis , nadph oxidase , mutant , respiratory burst , microbiology and biotechnology , biology , reactive oxygen species , plant immunity , mapk/erk pathway , biochemistry , chemistry , kinase , gene
Summary Plant recognition of pathogen‐associated molecular patterns ( PAMP s) such as bacterial flagellin‐derived flg22 triggers rapid activation of mitogen‐activated protein kinases ( MAPK s) and generation of reactive oxygen species ( ROS ). Arabidopsis has at least four PAMP /pathogen‐responsive MAPK s: MPK 3, MPK 6, MPK 4 and MPK 11. It was speculated that these MAPK s may function downstream of ROS in plant immunity because of their activation by exogenously added H 2 O 2 . MPK 3/ MPK 6 or their orthologs in other plant species have also been reported to be involved in the ROS burst from the plant respiratory burst oxidase homolog (Rboh) of the human neutrophil gp91phox. However, detailed genetic analysis is lacking. Using a chemical genetic approach, we generated a conditional loss‐of‐function mpk3 mpk6 double mutant. Consistent with results obtained using a conditionally rescued mpk3 mpk6 double mutant generated previously, the results obtained using the new conditional loss‐of‐function mpk3 mpk6 double mutant demonstrate that the flg22‐triggered ROS burst is independent of MPK 3/ MPK 6. In Arabidopsis mutants lacking a functional AtRbohD , the flg22‐induced ROS burst was completely blocked. However, activation of MPK 3/ MPK 6 was not affected. Based on these results, we conclude that the rapid ROS burst and MPK 3/ MPK 6 activation are two independent early signaling events in plant immunity, downstream of FLS 2. We also found that MPK 4 negatively affects the flg22‐induced ROS burst. In addition, salicylic acid pre‐treatment enhances the AtRbohD‐mediated ROS burst, which is again independent of MPK 3/ MPK 6 based on analysis of the mpk3 mpk6 double mutant. The establishment of an mpk3 mpk6 double mutant system using a chemical genetic approach provides a powerful tool to investigate the function of MPK 3/ MPK 6 in the plant defense signaling pathway.