Phosphoproteome analysis reveals new drought response and defense mechanisms of seedling leaves in bread wheat (Triticum aestivum L.).

Drought is a major form of abiotic stress that significantly affects plant growth and development. In this study, we performed the first phosphoproteome analysis of seedling leaves from two bread wheat cultivars (Hanxuan 10 and Ningchun 47) subjected to drought stress. As a result, a total of 191 and 251 unique phosphopeptides, representing 173 and 227 phosphoproteins in two cultivars, respectively, were identified as being significant changes in phosphorylation level (SCPL) under drought stress. Through the comparison of SCPL phosphoproteins between two cultivars, 31 common SCPL phosphoproteins were found in both cultivars. Function analysis showed that the SCPL phosphoproteins in the two cultivars are mainly involved in three biological processes: RNA transcription/processing, stress/detoxification/defense, and signal transduction. Further analyses revealed that some SCPL phosphoproteins may play key roles in signal transduction and the signaling cascade under drought stress. Furthermore, some phosphoproteins related to drought tolerance and osmotic regulation exhibited significant phosphorylation changes. This study used a series of bioinformatics tools to profile the phosphorylation status of wheat seedling leaves under drought stress with greater accuracy. BIOLOGICAL SIGNIFICANCE: Drought is of the most studied abiotic stresses, because it severely restricts the development and yield of plants. In this study, large numbers of stress-related phosphoproteins are identified from the two bread wheat cultivars. These phosphoproteins contribute to signal transduction, osmotic regulation and ROS scavenging under water stress. This work provides a detailed insight into the mechanisms of drought response and defense in bread wheat from the perspective of phosphoproteomics, and identifies some important drought-tolerant candidates for further transgenosis study and incorporation into the breeding of resistant cultivars.