Differences in Protein Expression and Ultrastructure between Two Wheat Near-Isogenic Lines Affected by Powdery Mildew

Wheat powdery mildew is caused by Blumeria graminis f. sp. tritici (Bgt). Pm21 is an effective broad-spectrum powdery mildew resistance gene, which shows a considerable promise in wheat breeding. We report here a proteomic approach to investigate the resistance response proteins after fungal infection and emphasize the resistance changes induced by Pm21. Two wheat (Triticum aestivum L.) near-isogenic lines (NILs), recurrent parent 'Bainong,' which is susceptible to powdery mildew, and its near-isogenic line 'W2132' carrying resistance gene Pm21) were used to investigate some changes in their proteomes after being infected. Proteins were extracted from the leaves sampled in 48 h after inoculation, separated by two-dimensional electrophoresis, and stained with Coomassie brilliant blue. Among these proteins, a total of 56 spots differentially expressed after Bgt infection were detected. Sixteen proteins, identified by MALDI-TOF-MS, exhibited more than a 1.5-fold increase upon fungal infection. Unfortunately, three spots were not identified successfully. The predicted functions of identified proteins were related to energy metabolism and defensive responses; they were involved in many physiological resistance responses, including enhancing energy metabolism, proteins synthesis and stabilization, antioxidant reactions, cell-wall reinforcement, and lignification. Interestingly that the expression of two proteins related to the cell-wall reinforcement was enhanced in the resistant line and one protein related to photosynthesis was lost in a susceptible line. By transmission electronic microscopy, the corresponding physiological characteristics were also observed. These results provide us with the information to further reveal the resistance mechanism of Pm21 action and comprehensively investigate the physiological response to powdery mildew at the protein level.