Sequential Regulation of Gibberellin, Brassinosteroid, and Jasmonic Acid Biosynthesis Occurs in Rice Coleoptiles to Control the Transcript Levels of Anti-Microbial Thionin Genes
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Transcripts of <I>thionin</I> genes encoding antimicrobial peptides were present at a high level in rice coleoptiles just after germination, and decreased to an undetectable level after about 3 d, but this decline was suppressed by co-treatment with gibberellic acid (GA<SUB>3</SUB>) and brassinolide (BL). The temporal expression patterns of key enzyme genes for the biosyntheses of gibberellins (GAs) and brassinosteroids (BRs) were correlated with the fluctuation of <I>thionin</I> mRNAs. Jasmonic acid (JA) replaced the effect of GA<SUB>3</SUB> and BL, and its change in endogenous level was parallel to that of the <I>thionin</I> genes. These results strongly suggest that <I>thionin</I> gene expression was positively regulated by JA, whose endogenous level was synergistically regulated by GAs and BRs. In contrast, <I>thionin</I> gene expression in etiolated seedlings remained high while the endogenous level of JA was low, suggesting the presence of another signaling pathway in the dark to maintain the <I>thionin</I> level.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(10), 2410-2419, 2006-10-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry