Overexpression of abiotic stress-induced AtMYBL-O results in negative modulation of abscisic acid signaling through the downregulation of abscisic acid-responsive genes in Arabidopsis thaliana

Abiotic stresses on plants are often associated with significant decreases in crop production. Plants have evolved a variety of mechanisms to regulate their growth and development to cope with these stresses. In this study, we characterize the gene AtMYBL-O, a member of the MYB-like transcription factor family, in Arabidopsis thaliana. Although high-salt concentrations and abscisic acid (ABA) induced the expression of AtMYBL-O, its upregulation by high-salt conditions was more significant, with its highest expression level detected in seedlings treated with 300 mM NaCl for 6.0 h. The AtMYBL-O protein localizes in the nucleus, implying that it might act as a transcription factor. Under abiotic stresses, the growth performance of AtMYBL-O-overexpressing (AtMYBL-O-OE) plants was significantly reduced compared with that of the A. thaliana Columbia-0 (Col-0) ecotype (wild-type) plants. In addition, in response to ABA, stress-responsive genes, including ABI1, ABI2, ABI5, COR15a, COR15b, COR47, and RD29A, showed lower expression in AtMYBL-O-OE than in Col-0 plants; therefore, the overexpression of AtMYBL-O has a negative function under abiotic stress conditions in A. thaliana.