MbWRKY50 confers cold and drought tolerance through upregulating antioxidant capacity associated with ROS scavenging

Abstract

Plant growth and development can be impacted by abiotic factors, including low temperature and dryness. Numerous studies have shown that plant responses to stress are largely influenced by the WRKY transcription factors (TFs). However, there are few studies on the role of WRKY genes in the stress response of Malus plants. In this experiment, Malus baccata (L.) Borkh was selected as the material, and the WRKY family gene MbWRKY50 was cloned using a gene cloning technique. Phylogenetic tree analysis revealed that MbWRKY50 and MdWRKY50 have the highest homology. Furthermore, a green fluorescent protein (GFP) fusion protein expression assay revealed that the MbWRKY50 protein is located in the nucleus. The results of RT-qPCR showed that the expression of MbWRKY50 was increased in the roots and fully grown leaves of M. baccata, and the response to low temperature and drought environment was enhanced. The MbWRKY50 gene was transferred into tomato, which could better adapt to the cold and dry living conditions. In contrast to wild-type (WT) and untransformed (UL) tomato lines, overexpression of MbWRKY50 boosts the activities of superoxide dismutase (SOD) and peroxidase (POD). Moreover, it leads to a notable reduction in the concentrations of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and superoxide anion free radicals (O₂⁻). The results showed that MbWRKY50 activated the expression levels of LeABI3, LeNCED1, LeABF4, LeDREB1, LeCBF1, and LeCBF3 by binding to cold binding factor/dehydration response element (CBF/DREB) or participating in ABA synthesis, thereby enhancing the resistance of transgenic tomatoes to low temperature and drought stress.