Proteomic analysis of the interaction between Plasmodiophora brassicae and Chinese cabbage (Brassica rapa L. ssp. Pekinensis) at the initial infection stage

Abstract The interaction between plants and pathogens that induces a defense response has been shown in previous studies. In our research, we used Plasmodiophora brassicae Woronin ( Plasmodiophoraceae ), the causal agent of clubroot disease, to infect the roots of Brassica rapa seedlings. Electron microscopic observation showed that the roots could be infected by Plasmodiophora brassicae on the fifth day after inoculation. We identified 438 and 414 differentially expressed proteins (DEPs) in the inoculated and control groups, respectively. Mass spectrometry was performed to identify 18 of the DEPs in which the relative protein abundance varied by >2-fold. In general, Gene Ontology (GO) analysis revealed that the DEPs reflected a wide range of molecular functions, including “response to stimuli” (39%) and “plant defense reaction” (8%) in the Biological Process domain. Among these, two proteins (DEPs 3038 and 3129) were found to be related to salicylic acid (SA)-mediated systemic acquired resistance (SAR), two proteins (DEPs 3414 and 2358) were found to be related to jasmonic acid (JA)/ ethylene (ET)-mediated induced systemic resistance (ISR), and DEP 4043 participated in both SAR and ISR. In addition, one pathogenesis-related protein (PR-1) was found in the extracellular cell component group, and KEGG analysis indicated that a DEP participates in plant-pathogen interaction signaling pathways. KEGG analysis also confirmed that these two pathways show some degree of cross-talk, rather than acting independently.