Plants are often exposed to biotic or abiotic stress, which can seriously impede their growth and development. In recent years, researchers have focused especially on the study of plant responses to biotic and abiotic stress. As one of the most widely planted grapevine rootstocks, ‘Beta’ has been extensively proven to be highly resistant to stress. However, further research is needed to understand the mechanisms of abiotic stress in ‘Beta’ rootstocks. In this study, we isolated and cloned a novel WRKY transcription factor, VhWRKY44, from the ‘Beta’ rootstock. Subcellular localization analysis revealed that VhWRKY44 was a nuclear-localized protein. Tissue-specific expression analysis indicated that VhWRKY44 had higher expression levels in grape roots and mature leaves. Further research demonstrated that the expression level of VhWRKY44 in grape roots and mature leaves was highly induced by salt and cold treatment. Compared with the control, Arabidopsis plants overexpressing VhWRKY44 showed stronger resistance to salt and cold stress. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly increased, and the contents of proline, malondialdehyde (MDA) and chlorophyll were changed considerably. In addition, significantly higher levels of stress-related genes were detected in the transgenic lines. The results indicated that VhWRKY44 was an important transcription factor in ‘Beta’ with excellent salt and cold tolerance, providing a new foundation for abiotic stress research.

In viticulture, the highly resistant rootstock ‘Beta’ is widely used in Chinese grape production to avoid the effects of soil salinization and drought on grape growth. However, the mechanism of high resistance to abiotic stress in the ‘Beta’ rootstock is not clear. In this study, we demonstrated that VhMYB2 as a transcription factor made a significant contribution to salinity and drought stress, which was isolated from the ‘Beta’ rootstock. The coding sequence of the VhMYB2 gene was 858 bp, encoding 285 amino acids. The subcellular localization of VhMYB2 was located in the nucleus of tobacco epidermal cells. Moreover, RT-qPCR found that VhMYB2 was predominantly expressed in the mature leaf and root of the grape. Under salinity and drought stress, overexpressing VhMYB2 showed a higher resistant phenotype and survival rates in A. thaliana while the transgenic lines had a survival advantage by measuring the contents of proline, chlorophyll, and MDA, and activities of POD, SOD, and CAT, and expression levels of related stress response genes. The results reveal that VhMYB2 may be an important transcription factor regulating ‘Beta’ resistance in response to abiotic stress.

Cold and drought stress considerably suppress the development of plants. In this study, a new MYB (v-myb avian myeloblastosis viral)TF gene, MbMYBC1, was isolated from the M. baccata and located in nucleus. MbMYBC1 has a positive response to low temperature and drought stress. After being introduced into Arabidopsis thaliana, the physiological indicators of transgenic Arabidopsis had corresponding changes under these two stresses, the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) increased, electrolyte leakage rate (EL) and the content of proline increased, but the content of chlorophyll decreased. In addition, its overexpression can also activate the downstream expression of AtDREB1A, AtCOR15a, AtERD10B and AtCOR47 related to cold stress and AtSnRK2.4, AtRD29A, AtSOD1and AtP5CS1 related to drought stress. Based on these results, we speculate that MbMYBC1 can respond to cold and hydropenia signals, and can be used in transgenic technology to improve plant tolerance to low temperature and drought stress.

Apple is an important horticultural crop, but various adverse environmental factors can threaten the quality and yield of its fruits. The ability of apples to resist stress mainly depends on the rootstock. Malus baccata (L.) Borkh. is a commonly used rootstock in Northeast China. In this study, it was used as the experimental material, and the target gene MbWRKY53 was screened through transcriptome analysis and Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction (RT-qPCR) after cold and drought treatment. Bioinformatics analysis revealed that this transcription factor (TF) belonged to the WRKY TF family, and its encoded protein was localized in the nucleus. RT-qPCR showed that the gene was more easily expressed in roots and young leaves and is more responsive to cold and drought stimuli. Functional validation in Arabidopsis thaliana confirmed that MbWRKY53 can enhance plant tolerance to cold and drought stress. Furthermore, by analyzing the expression levels of genes related to cold and drought stress in transgenic Arabidopsis lines, it was inferred that this gene can regulate the expression of stress-related genes through multiple pathways such as the CBF pathway, SOS pathway, Pro synthesis pathway, and ABA-dependent pathways, enhancing the adaptability of transgenic Arabidopsis to cold and drought environments.

The WRKY transcription factor family is a significant family of plant transcription factors (TFs). Plant growth and development are often influenced by abiotic factors, such as salinity and low temperature. Numerous studies have demonstrated that WRKY TFs primarily influence plant responses to adversity. However, there are few studies on the role of WRKY genes in the stress responses of Malus baccata (L.) Borkh. We cloned the MbWRKY33 gene from Malus baccata for this research, and its roles in salt stress tolerance were analyzed. Phylogenetic tree analysis revealed that MbWRKY33 and PbWRKY33 have the highest homology. Subcellular localization revealed that MbWRKY33 was located within the nucleus. An analysis of tissue-specific expression showed that MbWRKY33 had relatively high expression levels in young leaves and roots. Moreover, Arabidopsis thaliana plants overexpressing MbWRKY33 exhibited stronger resistance to salt stress compared with the wild type (WT) and the unloaded line empty vector (UL). Under the treatment of 200 mM NaCl, transgenic Arabidopsis thaliana plants exhibited significantly higher activities of antioxidant enzymes like superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) than the control. In contrast, the WT and the UL lines had elevated levels of malondialdehyde (MDA) and reactive oxygen species (ROS). In addition, MbWRKY33 elevates transgenic plant resistance to salt stress by regulating the expression levels of AtNHX1, AtSOS1, AtSOS3, AtNCED3, AtSnRK2, and AtRD29a. Results indicated that MbWRKY33 in Malus might be linked to high-salinity stress responses, laying a foundation for understanding WRKY TFs’ reaction to such stress.

The living environment of plants is not static; as such, they will inevitably be threatened by various external factors for their growth and development. In order to ensure the healthy growth of plants, in addition to artificial interference, the most important and effective method is to rely on the role of transcription factors in the regulatory network of plant responses to abiotic stress. This study conducted bioinformatics analysis on the MbWRKY46 gene, which was obtained through gene cloning technology from Malus baccata (L.) Borkh, and found that the MbWRKY46 gene had a total length of 1068 bp and encodes 355 amino acids. The theoretical molecular weight (MW) of the MbWRKY46 protein was 39.76 kDa, the theoretical isoelectric point (pI) was 5.55, and the average hydrophilicity coefficient was −0.824. The subcellular localization results showed that it was located in the nucleus. After conducting stress resistance studies on it, it was found that the expression of MbWRKY46 was tissue specific, with the highest expression level in roots and old leaves. Low temperature and drought had a stronger induction effect on the expression of this gene. Under low temperature and drought treatment, the expression levels of several downstream genes related to low temperature and drought stress (AtKIN1, AtRD29A, AtCOR47A, AtDREB2A, AtERD10, AtRD29B) increased more significantly in transgenic Arabidopsis. This indicated that MbWRKY46 gene can be induced to upregulate expression in Arabidopsis under cold and water deficient environments. The results of this study have a certain reference value for the application of M. baccata MbWRKY46 in low-temperature and drought response, and provide a theoretical basis for further research on its function in the future.