Analysis Of Transcriptome In Chinese Cabbage Infected By Plasmodiophora Brassicae At The Initial Stage

Clubroot is a high-incidence disease of Chinese cabbage,which can lead to a significant reduction in the yield of Chinese cabbage,but the molecular mechanism of resistance to clubroot is still unclear.In this study,a susceptible variety to Plasmodiophora brassicae of Chinese cabbage ‘SN742' was infected by race 4,the dominant physiological race of Plasmodiophora brassicae.The root at the initial stage of infection and the non-infected control at the same time were taken for transcriptome sequencing analysis.The possible molecular mechanism of resistance to clubroot in Chinese cabbage was analyzed by cluster analysis,q RT-PCR and bioinformatics.The content of peroxidase(POD),salicylic acid(SA)and jasmonic acid(JA)in the roots of susceptible cultivar `SN742' and resistant quality‘SN205' were determined at different stages of infection.1.Infection of susceptible Chinese cabbage ‘SN742' was carried out by using physiological race 4 of Plasmodiophora brassicae with different concentrations(8.89 x 105,9.76 x 105,1.08 x 106,1.21 x 106,1.38 x 106,1.6 x 106)(per m L)combined with agarose coating method.The best concentration of bacterial solution was 1.21 x 106/m L,and the best concentration was on the 8th day after infection.2.Through RNA-seq analysis of Chinese cabbage roots at the early stage of Plasmodiophora brassicae infection,we found that a large number of genes involved in the interaction between Chinese cabbage and Plasmodiophora brassicae came from NBS-LRR resistance genes,metabolic pathways,PRRs,autophagy-related genes,stimulus responserelated genes and transcription factor-related genes,respectively.3.Detection of POD values in roots of resistant and susceptible materials during infection and pathogenesis showed that POD was significantly increased after inoculation by Plasmodiophora brassicae But the increace range depends on infection stage and materia resistance.So,POD should to protect the resistant and susceptible plant s at the initial stage of infection and also to protect the susceptible plant s at diseased stage4.Through the detection of SA content in roots of resistant and susceptible materials during infection and pathogenesis,combined with the results of transcriptome sequencing,we found that several SA-related genes participated in the process of interaction between Plasmodiophora brassicae and Chinese cabbage.The SA content increased significantly after inoculation,and the SA content in pathogenesis was significantly higher than that in pathogenesis,and the SA content was also related to materials.Therefore,SA might be the cause of disease-resistant varieties of Chinese cabbage to Plasmodiophora brassicae,one of the reasons for resistance.5.By detecting JA content in roots of resistant and susceptible materials during infection and pathogenesis,combined with the results of transcriptome sequencing,it was found that JA-related genes were involved in the interaction between Plasmodiophora brassicae and Chinese cabbage during infection.JA content changed opposite in different materials before and after inoculation.JA content of susceptible materials increased after inoculation,while that of resistant materials decreased after inoculation,which also indicated JA content.It is related to different materials.Based on the above results,we conclude that the main regulative genes in the early stage of Plasmodiophora brassicae infection in Chinese cabbage are disease resistance-related genes,PRRs,POD-related genes,SA-related genes and JA-related genes.POD,SA,JA should be main complete to resistant the infection of Plasmodiophora brassicae.These results provide important clues for clarifying the molecular mechanism of resistance to Plasmodiophora brassicae infection in Chinese cabbage.