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Nuclear ubiquitin proteasome degradation affects WRKY 45 function in the rice defense program
Author(s) -
Matsushita Akane,
Inoue Haruhiko,
Goto Shingo,
Nakayama Akira,
Sugano Shoji,
Hayashi Nagao,
Takatsuji Hiroshi
Publication year - 2013
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.12035
Subject(s) - wrky protein domain , proteasome , salicylic acid , biology , ubiquitin , microbiology and biotechnology , ubiquitin ligase , regulator , biochemistry , gene , gene expression , transcriptome
Summary The transcriptional activator WRKY 45 plays a major role in the salicylic acid/benzothiadiazole‐induced defense program in rice. Here, we show that the nuclear ubiquitin–proteasome system ( UPS ) plays a role in regulating the function of WRKY 45. Proteasome inhibitors induced accumulation of polyubiquitinated WRKY 45 and transient up‐regulation of WRKY 45 target genes in rice cells, suggesting that WRKY 45 is constantly degraded by the UPS to suppress defense responses in the absence of defense signals. Mutational analysis of the nuclear localization signal indicated that UPS ‐dependent WRKY 45 degradation occurs in the nuclei. Interestingly, the transcriptional activity of WRKY 45 after salicylic acid treatment was impaired by proteasome inhibition. The same C ‐terminal region in WRKY 45 was essential for both transcriptional activity and UPS ‐dependent degradation. These results suggest that UPS regulation also plays a role in the transcriptional activity of WRKY 45. It has been reported that A t NPR 1, the central regulator of the salicylic acid pathway in A rabidopsis, is regulated by the UPS . We found that O s NPR 1/ NH 1, the rice counterpart of NPR 1, was not stabilized by proteasome inhibition under uninfected conditions. We discuss the differences in post‐translational regulation of salicylic acid pathway components between rice and A rabidopsis.