The WRKY transcription factors are unique regulatory proteins in plants, which are important in the stress responses of plants. In this study, 113 WRKY genes were identified from the apple genome GDDH13 and a comprehensive analysis was performed, including chromosome mapping, and phylogenetic, motif and collinearity analysis. MdWRKYs are expressed in different tissues, such as seeds, flowers, stems and leaves. We analyzed seven WRKY proteins in different groups and found that all of them were localized in the nucleus. Among the 113 MdWRKYs, MdWRKY70L was induced by both drought and salt stresses. Overexpression of it in transgenic tobacco plants conferred enhanced stress tolerance to drought and salt. The malondialdehyde content and relative electrolyte leakage values were lower, while the chlorophyll content was higher in transgenic plants than in the wild-type under stressed conditions. In conclusion, this study identified the WRKY members in the apple genome GDDH13, and revealed the function of MdWRKY70L in the response to drought and salt stresses.

No abstract

No abstract

Summary RAD23 (RADIATION SENSITIVE23) proteins are a group of UBL‐UBA (ubiquitin‐like‐ubiquitin‐associated) proteins that shuttle ubiquitylated proteins to the 26S proteasome for breakdown. Drought stress is a major environmental constraint that limits plant growth and production, but whether RAD23 proteins are involved in this process is unclear. Here, we demonstrated that a shuttle protein, MdRAD23D1, mediated drought response in apple plants (Malus domestica). MdRAD23D1 levels increased under drought stress, and its suppression resulted in decreased stress tolerance in apple plants. Through in vitro and in vivo assays, we demonstrated that MdRAD23D1 interacted with a proline‐rich protein MdPRP6, resulting in the degradation of MdPRP6 by the 26S proteasome. And MdRAD23D1 accelerated the degradation of MdPRP6 under drought stress. Suppression of MdPRP6 resulted in enhanced drought tolerance in apple plants, mainly because the free proline accumulation is changed. And the free proline is also involved in MdRAD23D1‐mediated drought response. Taken together, these findings demonstrated that MdRAD23D1 and MdPRP6 oppositely regulated drought response. MdRAD23D1 levels increased under drought, accelerating the degradation of MdPRP6. MdPRP6 negatively regulated drought response, probably by regulating proline accumulation. Thus, “MdRAD23D1‐MdPRP6” conferred drought stress tolerance in apple plants.