Overexpression of a Malus baccata (L.) Borkh WRKY transcription factor gene MbWRKY65 increased the tolerance to cold and drought in transgenic tomato

Abstract

Plants exposed to harsh external environments such as cold and drought display stunted growth and delayed development. WRKY proteins can bind to the cis-acting element W-box to activate or repress transcription of downstream target genes to regulate responses, including different abiotic and biotic stresses. In this experiment, Malus baccata (L.) Borkh was used to isolate the MbWRKY65 gene to study its cold and drought resistance functions. The outcomes demonstrated that MbWRKY65 is most similar to the apple MdWRKY65 protein. Its location in the nucleus is shown by subcellular localization data, which is in line with its role as a transcription factor. MbWRKY65 was expressed richer in roots and older leaves in response to cold and drought treatments. The transgenic tomato showed considerably reduced contents of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), superoxide anion radical (O₂⁻), and relative conductivity during cold and drought stress in contrast to wild-type (WT) and unloaded lines (UL), but greater contents of proline and chlorophyll, as well as higher activity of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Stress-related genes (LeCBF1, LeABI3, LeABF4, LeCBF3, LeNCED1, and LeDREB1) in transgenic tomato plants were positively regulated under conditions of cold and drought, and in contrast to the WT and UL lines, the transgenic tomato showed a considerably greater expression level. In conclusion, MbWRKY65 actively contributes to plant tolerance to cold and drought.