The gain-of-function mutation of the rice auxin-signaling repressor, OsIAA13, induces rice bacterial blight resistance through activating jasmonic acid-mediating defense system
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Jasmonic acid (JA) is involved in the regulation of rice defense responses against Xanthomonas oryzae pv. oryzae ( Xoo ). JA also affects other plant hormone signaling to maximize the JA-induced defense responses in rice. In this study, we investigated the JA- and auxin-mediating defense system using a gain-of-function mutant of OsIAA13, a suppressor of auxin signaling, in rice. The expression of some auxin-responsive expansin s was downregulated in the Osiaa13 mutants. The Osiaa13 mutants showed a JA-hypersensitive phenotype. The expression of some JA-responsive defense-related genes such as the lignin biosynthesis gene, OsPrx38 , was upregulated in the Osiaa13 mutants. Lignin content was higher in the Osiaa13 mutants than in the wild type plants. The expression of OsPrx38 was downregulated after IAA treatment. Furthermore, some antibacterial compounds against Xoo accumulated in the Osiaa13 mutants. These results suggest that OsIAA13 has an important role in disease resistance against Xoo by regulating JA- and auxin-mediating defense system in rice.
