Cell wall proteome of wheat roots under flooding stress using gel-based and LC MS/MS-based proteomics approaches

Cell wall proteins (CWPs) are important both for maintenance of cell structure and for responses to abiotic and biotic stresses. In this study, a destructive CWP purification procedure was adopted using wheat seedling roots and the purity of the CWP extract was confirmed by minimizing the activity of glucose-6-phosphate dehydrogenase, a cytoplasmic marker enzyme. To determine differentially expressed CWPs under flooding stress, gel-based proteomic and LC-MS/MS-based proteomic techniques were applied. Eighteen proteins were found to be significantly regulated in response to flood by gel-based proteomics and 15 proteins by LC MS/MS-based proteomics. Among the flooding down-regulated proteins, most were related to the glycolysis pathway and cell wall structure and modification. However, the most highly up-regulated proteins in response to flooding belong to the category of defense and disease response proteins. Among these differentially expressed proteins, only methionine synthase, beta-1,3-glucanases, and beta-glucosidase were consistently identified by both techniques. The down-regulation of these three proteins suggested that wheat seedlings respond to flooding stress by restricting cell growth to avoid energy consumption; by coordinating methionine assimilation and cell wall hydrolysis, CWPs played critical roles in flooding responsiveness.