Molecular Mechanism Of Post-invasion Defense Against Tabacco Powdery Mildew In Arabidopsis

Powdery mildew is a common and serious fungal disease that is harmful to agriculture.Understanding the pathogenic mechanism of powdery mildew has important significance for agriculture.Resistance is divided into pre-invasion resistance and post-invasion resistance according to the location.The pathogenicity of tobacco powdery mildew Gc SICAU1 is weak.When Gc SICAU1 is inoculated on the Arabidopsis thaliana wild type Col-0 and the double mutant pad4-1 sid2-1,Gc SICAU1 can break through the pre-invasion resistance and form haustoria,but its further growth is suppressed by post-invasion resistance in Col-0,while it grows well in the double mutant pad4-1 sid2-1,which indicates that the post-invasion resistance in the double mutant pad4-1 sid2-1 is lost.So the differential expressed genes(DEGs)between Col-0 and pad4-1 sid2-1 reveal the network of post-invasion resistance genes.To explore the molecular mechanism of post-invasion resistance against tabacco powdery mildew in Arabidopsis,the tobacco powdery mildew Gc SICAU1 was inoculated on six-week-old Col-0 and pad4-1 sid2-1 in this research,then leaf samples were taken at 0,1,3,6,8,10,12 days post inoculation respectively to extract RNA and do RNA-seq,finally GO and KEGG enrichment analysis were performed.The main results are described as followings:(1)The DEGs in Col-0 and pad4-1 sid2-1 were analyzed respectively in order to understand the response to tobacco powdery mildew in plants.In Col-0,the mainly induced genes involve in defense.Salicylic acid-related genes are induced highly.In pad4-1 sid2-1,the resistance processes are delayed and weak.The mainly induced genes involve in detoxification and secondary metabolism.(2)We analysed DEGs between Col-0 and pad4-1 sid2-1 at the same time point.The results show that the DEGs which expressed higher in Col-0 compared with pad4-1 sid2-1 are mainly enriched in following GO terms:response to salicylic acid and jasmonate acid,respiratory burst,systemic acquired resistance,hypersensitive response,plant-pathogen interaction and so on.These processes are the main processes of post-invasion resistance.The DEGs which expressed higher in pad4-1 sid2-1 compared with Col-0 are mainly enriched in following GO terms:toxin catabolism,nutrient transport,secondary metabolite synthesis and metabolism,and so on.These processes are closely related to mitigate the toxicity of powdery mildew and maintain its own growth.(3)We analysed expression patterns of DEGs in Col-0 and pad4-1 sid2-1,clusters with similar trend were classified into one group.There are 9 groups in all,including 2286 genes.According to the expression trend,the gene expression level of 4 groups in Col-0 is higher than that in pad4-1 sid2-1,and these genes mainly involve in resistance process.The gene expression level of 5 groups in pad4-1 sid2-1 is higher than in Col-0,and these genes mainly involve in susceptible process.(4)To deeply dissect genes related to disease resistance,we analysised protein kinase-related genes,salicylic acid-related genes,phenylpropanoid biosynthesis genes,and plant-pathogen interaction network genes.Some important genes about post-invasion resistance were found.(5)19 important genes were chosen to do qRT-PCR verification,the 19 genes involve in different expression pattern.The results showed that the results of qRT-PCR were consistent with RNA-seq,which indicates the results of RNA-seq are reliable.The results of this research allow us to have more comprehensive and intuitive understanding of the post-invasive resistance mechanism,and provide abundant data to support for the further study of post-invasion resistance.The results of this study allow us to have a preliminary understanding of the mechanism of post-invasive resistance,and provide abundant data support for further study of post-invasion resistance.