Abstract
Jasmonates (JAs) are phytohormones derived from oxygenated fatty acids and regulates a broad range of plant defense and development processes. Here we describe another function of JAs: hypocotyl elongation under various light conditions was suppressed by exogenous methyl jasmonate (MeJA) treatment in Arabidopsis. Mutant analyses suggest that SCFCOI1-mediated proteolysis is required for this function. However, (+)-7-iso-JA-L-Ile was showed weaker effect than MeJA under dark and red light. Under blue light, gibberellin (GA) abolished the jasmonate function on hypocotyl elongation. This result suggests a crosstalk between JA and GA signaling. By screening of EMS mutant seeds, three mutants insensitive to MeJA on hypocotyl elongation, jal1 (jasmonate resistance long hypocotyl 1), jal36 and jal17 were isolated. Further analysis indicates that both jal1 and jal36 have a mutation in phytochrome B gene. These results suggest that jasmonate signaling is partially involved in phytomorphogenesis through phytochrome B and SCFCOI1 dependent pathway mediated by (+)-7-iso-JA-L-Ile and other jasmonate derivatives.
