Jasmonate-Inducible R2R3-MYB Transcription Factor Regulates Capsaicinoid Biosynthesis and Stamen Development in <i>Capsicum</i>

Abstract

Jasmonates (JAs) play an important role in plant developmental processes and regulate the biosynthesis of various specialized metabolites, and transcription factors are crucial in mediating JA signaling to regulate these processes. Capsaicinoids (Caps) are intriguing specialized metabolites produced uniquely by <i>Capsicum</i> species that give their fruits a pungent flavor to defend against herbivory and pathogens. In this study, we identify a R2R3-MYB transcription factor <i>CaMYB108</i> and demonstrate its roles in regulating the biosynthesis of Caps and stamen development. Transcriptional analysis indicated that <i>CaMYB108</i> was preferentially expressed in the flower and fruit, while the subcellular localization of <i>CaMYB108</i> was shown to be the nucleus. Virus-induced gene silencing of <i>CaMYB108</i> led to the expression of capsaicinoid biosynthetic genes (CBGs), and the contents of Caps dramatically reduce. Moreover, the <i>CaMYB108</i>-silenced plants showed delayed anther dehiscence and reduced pollen viability. Transient overexpression of <i>CaMYB108</i> caused the expression of CBGs to be upregulated, and the Caps content significantly increased. The results of dual-luciferase reporter assays showed that <i>CaMYB108</i> targeted CBG promoters. In addition, the expression of <i>CaMYB108</i> and CBGs was inducible by methyl jasmonate and was consistent with the increased content of Caps. Overall, our results indicate that <i>CaMYB108</i> is involved in the regulation of Caps biosynthesis and stamen development.