Proteomic analysis of non-heading Chinese cabbage infected with Hyaloperonospora parasitica

Abstract

Downy mildew is a serious fungal disease in non-heading Chinese cabbage (Brassica campestris ssp. chinensis Makino) that is caused by Hyaloperonospora parasitica, which infects members of the Brassicaceae family. For breeding improvement, researchers must understand the defence mechanisms employed by non-heading Chinese cabbage to combat H. parasitica infection. Using 2-DE protein analysis, we compared the proteomes from leaves of non-heading Chinese cabbage seedlings that were infected with H. parasitica or that were only treated with water at different time points post-infection. By MS analysis, 91 protein spots with significant differences in abundance (>2-fold, p<0.05) were identified in mock- and H. parasitica-inoculated leaves. Next, a resistance strategy for incompatible interactions was proposed. This network consisted of several functional components, including enhanced ethylene biosynthesis and energy supply, balanced ROS production and scavenging, accelerated protein metabolism and photorespiratory, reduced photosynthesis, and induced photosystem repair. These findings increase our knowledge of incompatible interactions between plants and pathogens and also provide new insight regarding the function of plant molecular processes, which should assist in the discovery of new strategies for pathogen control. This study reported the proteomic analysis of the incompatible interactions between non-heading Chinese cabbage and downy mildew using 2-DE and MS. In total, 91 protein spots that were related to the resistance response were identified. These proteins were assigned to different functional categories, such as amino acid and carbohydrate metabolism, photosynthesis and photorespiration, protein metabolism, signal transduction, redox homeostasis, and ethylene biosynthesis. Meanwhile, several key proteins were determined to be associated with ethylene signalling, ROS scavenging and resistance-related proteins. Consistent with these results, the expression of ethylene biosynthesis genes and response genes, as well as the activity of antioxidant enzymes, increased after inoculation. These findings provide new insight for further understanding the molecular mechanisms of plant resistance.