Cytochrome P450 CYP94B3 mediates catabolism and inactivation of the plant hormone jasmonoyl-L-isoleucine

摘要

The phytohormone jasmonoyl-L-isoleucine (JA-lle) signals through the COI1-JAZ coreceptor complex to control key aspects of plant growth, development, and immune function. Despite detailed knowledge of the JA-lle biosynthetic pathway, little is known about the genetic basis of JA-lle catabolism and inactivation. Here, we report the identification of a wound- and jasmonate-responsive gene from Arabidopsis that encodes a cytochrome P450 (CYP94B3) involved in JA-lle turnover. Metabolite analysis of wounded leaves showed that loss of CYP94B3 function in cyp94b3 mutants causes hyperaccumulation of JA-lle and concomitant reduction in 12-hy-droxy-JA-lle (12OH-JA-lle) content, whereas overexpression of this enzyme results in severe depletion of JA-lle and corresponding changes in 12OH-JA-lle levels. In vitro studies showed that heter-ologously expressed CYP94B3 converts JA-lle to 12OH-JA-lle, and that 12OH-JA-lle is less effective than JA-lle in promoting the formation of COI1-JAZ receptor complexes. CYP94B3-overexpressing plants displayed phenotypes indicative of JA-lle deficiency, including defects in male fertility, resistance to jasmonate-induced growth inhibition, and susceptibility to insect attack. Increased accumulation of JA-lle in wounded cyp94b3 leaves was associated with enhanced expression of jasmonate-responsive genes. These results demonstrate that CYP94B3 exerts negative feedback control on JA-lle levels and performs a key role in attenuation of jasmonate responses.