Abstract
Phytohormones are involved in various aspects of plant growth and development. Jasmonates (JAs) form one class of plant hormones, and regulate various physiological events such as plant growth, defense response to wounding and pathogens, senescence, and floral organogenesis. Although COI1-JAZ signaling system is known to be a central regulator in the jasmonate signaling, downstream factors that regulate JA responsive genes (JRG) are still unclear. In this study, we identified a novel JA responsive gene CHJ (constitutively hypersensitive to jasmonate), co-expressing with JA-responsive transcription factors. Moreover, we found that CHJ acts as a negative regulator in JA-signaling. Arabidopsis thaliana CHJ knock-out mutant chj showed a response with a lower concentration of JA compared to wild type. It was suggested that the chj mutant is hypersensitive to JA. Moreover, expression of a plant defensin (PDF1.2) cooperatively regulated by JA and ethylene signaling was upregulated without JA treatment in the mutant. These results suggested that CHJ suppresses JA signaling specifically in the JA and ethylene signaling crosstalk.
