Adventitious root development is affected by methyl jasmonate in Arabidopsis thaliana

Auxin stimulates adventitious root (AR) formation in planta and in vitro cultured explants. In Arabidopsis plantlets grown in vitro ARs can be induced on the hypocotyl, without exogenous auxin, by etiolating seedlings in the dark. In Arabidopsis thin cell layer (TCL) system, the stem cortical tissues are re-programmed by exogenous auxin in combination with low cytokinin under darkness to regenerate ARs. AR formation is also a stress induced response and it was previously shown that jasmonates can be involved in the regulation of adventitious rooting. In addition it is known that jasmonates positively affect auxin biosynthesis in Arabidopsis. In order to better understand the role of jasmonates, we investigated the effect of MeJA, and its interaction with auxin, during AR formation in planta and in TCLs of Arabidopsis. Various MeJA concentrations were applied under hormone-free conditions and in the presence of IBA and Kinetin. Two mutants affected in jasmonic acid biosynthesis (dde2-2 and opr3) and the mutant sur2-1 known to spontaneously produce ARs due to an increased endogenous auxin level were used for the purpose. AtGH3-3, AtGH3-5, and AtGH3-6 are auxin-inducible genes whose protein level correlates positively with AR development in planta, and are up-regulated in sur2-1. Their expression was monitored during AR formation in planta and in TCLs, in the presence/absence of MeJA. All together, our results suggest an interaction between jasmonates and auxin during AR formation, in Arabidopsis.