The BoMIEL1–BoMYB96 Module Responds to ABA Signals to Enhance the Drought Tolerance of Cabbage ( Brassica oleracea var . capitata )

ABSTRACT

Cabbage ( Brassica oleracea var . capitata ) is an important vegetable crop. Drought is a major abiotic stress during its growth and severely reduces crop yield and quality. Consequently, research focused on enhancing the drought tolerance of cabbage is essential. MYB is one of the largest transcription factor families in plants, playing a crucial regulatory role in the plant's response to drought stress. However, the research on MYB transcription factors in cabbage remains limited. Previous studies show that MYB96 regulates the plant drought tolerance by responding to ABA signals. In this experiment, we cloned the BoMYB96 gene from cabbage and found that it significantly enhanced the drought stress tolerance of transgenic plants. Overexpression of BoMYB96 reduced oxidative damage under drought stress and increased proline content, while the opposite phenotype was observed in the cabbage silenced lines, BoMYB96‐silenced lines exhibited more severe oxidative damage than the control and had a significantly lower survival rate compared with the control. Additionally, we found that the E3 ubiquitin ligase MYB30‐INTERACTING E3 LIGASE 1 (BoMIEL1) in cabbage could mediate the ubiquitination and degradation of BoMYB96, and this process was inhibited by ABA. During the drought stress stage, the endogenous ABA content in plants increased, inhibiting the BoMIEL1 mediated ubiquitination of BoMYB96. As a result, the BoMYB96 protein accumulated, improving the plant's drought stress tolerance. These results provide a reference for applying MYB family gene functions in cabbage and offer a theoretical basis for breeding drought‐tolerant varieties.