Overexpression of a Malus baccata MYB Transcription Factor Gene MbMYB4 Increases Cold and Drought Tolerance in Arabidopsis thaliana

In the natural environment, plants often face unfavorable factors such as drought, cold, and freezing, which affect their growth and yield. The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family is widely involved in plant responses to biotic and abiotic stresses. In this study, Malus baccata (L.) Borkh was used as the research material, and a gene MbMYB4 of the MYB family was cloned from it. The open reading frame (ORF) of MbMYB4 was found to be 762 bp, encoding 253 amino acids; sequence alignment results and predictions of the protein structure indicated that the MbMYB4 protein contained the conserved MYB domain. Subcellular localization showed that MbMYB4 was localized in the nucleus. In addition, the use of quantitative real-time PCR (qPCR) technology found that the expression of MbMYB4 was enriched in the young leaf and root, and it was highly affected by cold and drought treatments in M. baccata seedlings. When MbMYB4 was introduced into Arabidopsis thaliana, it greatly increased the cold and drought tolerance in the transgenic plant. Under cold and drought stresses, the proline and chlorophyll content, and peroxidase (POD) and catalase (CAT) activities of transgenic A. thaliana increased significantly, and the content of malondialdehyde (MDA) and the relative conductivity decreased significantly, indicating that the plasma membrane damage of transgenic A. thaliana was lesser. Therefore, the overexpression of the MbMYB4 gene in A. thaliana can enhance the tolerance of transgenic plants to cold and drought stresses.