Preliminary Analysis Of The Roles Of MYCs In MeJA-elicited Indolic Glucosinolates Biosynthesis

Glucosinolates are a group of sulfur-rich thioglucosides and are known to play an important role in plant defense and benefit human health. Many studies have demonstrated that the accumulation of indolic glucosinolates (IGS) is strong induced by jasmonate (JA). However, the underlying molecular mechanism for JA-induced IGS accumulation remains only partly understood. Firstly, we combine the method of genetics and molecular strategies to identify the homozygous mutant of MYC2and COll, which is the fundamental genes in JA signaling, as well as homozygous mutant of MYB51, an important gene regulating the biosynthesis of indole glucosinonates. Then, we ues myc2mutant and the wild-type (WT) plants which were treated with MeJA to test the expression of MYCs, MYB51, MYB34, as well as the indolic glucosinonates biosynthesis genes. Quantitative RT-PCR revealed that the expression of MYC3and MYC4, the closest homologs of MYC2, was induced to a higher level in myc2mutants compared with WT plants after6h of MeJA treatment. Likewise, the transcript of MYB34, a known positive regulator of IGS biosynthesis, also showed a remarkable increase at6h in MeJA-treated myc2mutants relative to that in MeJA-treated WT plants. Then, accordingly, the expression of tryptophan biosynthetic genes (ASAl, TSAl, and TSBl) was identified to be up-regulated at6h, but the induction of IGS biosynthetic genes (CYP79B2, CYP79B3, and CYP83B1) showed temporally delayed increase at24h.Ultimately, the total IGS was detected to be increased at24h after MeJA treatment in myc2mutants. Taken together, the compensatory activation of MYC3and MYC4in MeJA-treated myc2mutants occurs temporally coordinated with the concurrent increase of IGS biosynthesis, providing new insight into the negative role of MYC2in JA-induced IGS biosynthesis.