<i>AtMOB1</i> Genes Regulate Jasmonate Accumulation and Plant Development

Abstract

The MOB1 proteins are highly conserved in yeasts, animals, and plants. Previously, we showed that the Arabidopsis (<i>Arabidopsis thaliana</i>) <i>MOB1A</i> gene (<i>AtMOB1A/NCP1</i>) plays critical roles in auxin-mediated plant development. Here, we report that <i>AtMOB1A</i> and <i>AtMOB1B</i> redundantly and negatively regulate jasmonate (JA) accumulation and function in Arabidopsis development. The two <i>MOB1</i> genes exhibited similar expression patterns, and the MOB1 proteins displayed similar subcellular localizations and physically interacted in vivo. Furthermore, the <i>atmob1a atmob1b</i> (<i>mob1a/1b</i>) double mutant displayed severe developmental defects, which were much stronger than those of either single mutant. Interestingly, many JA-related genes were up-regulated in <i>mob1a/1b</i>, suggesting that AtMOB1A and AtMOB1B negatively regulate the JA pathways. <i>mob1a/1b</i> plants accumulated more JA and were hypersensitive to exogenous JA treatments. Disruption of <i>MYC2</i>, a key gene in JA signaling, in the <i>mob1a/1b</i> background partially alleviated the root defects and JA hypersensitivity observed in <i>mob1a/1b.</i> Moreover, the expression levels of the <i>MYC2</i>-repressed genes <i>PLT1</i> and <i>PLT2</i> were significantly decreased in the <i>mob1a/1b</i> double mutant. Our results showed that <i>MOB1A/1B</i> genetically interact with <i>SIK1</i> and antagonistically modulate JA-related gene expression. Taken together, our findings indicate that AtMOB1A and AtMOB1B play important roles in regulating JA accumulation and Arabidopsis development.