AtMybL-O modulates abscisic acid biosynthesis to optimize plant growth and ABA signaling in response to drought stress

To combat constant stress from the external environment throughout their life cycle, plants have evolved their own defense mechanisms. Through robust and complicated defense mechanisms, plants have increased their productivity and adaptability under harsh conditions. In this study, we demonstrated the function of the AtMybL-O gene by using knockout (ko) mutants to expand the existing research field. The atmybl-o ko mutant seedlings grew similarly to the wild type (WT) in response to osmotic stress, while the AtMybL-O overexpression lines exhibit growth suppression in the same growth condition. Further, we attempted to understand the functional mechanism of AtMybL-O with respect to stress response toward drought stress. Firstly, we determined the changes in gene expression of the mutants in response to mannitol treatment and identified a strong increase in the expression of COR15b, DREB1A, and NCED3 gene in the mutant. Finally, through abscisic acid (ABA) measurement experiments, we observed that the ABA content of mannitol-treated mutants was higher than that of the WT. Therefore, our results indicate that AtMybL-O modulates ABA biosynthesis and ABA signaling in response to drought stress.