Preliminary Analysis Of The Mechanism Of R3a-Avr3a Mediated HR To Late Blight

Late blight is caused by Phytophthora infestans,which can cause great harm to solanaceae crops.P.infestans is a kind of pathogen with great evolutionary potential and complex physiological species,so it is called "plant resistance gene destroyers".Research on the resistance mechanism of disease resistance genes can help us understand the disease resistance mechanism of plants and improve the broad-spectrum resistance of plants to pathogens.Hypersensitive response(HR)is a landmark event of ETI resistance pathway that all resistance genes participate in.Understandingthe process of HR will help us to deeply analyze the resistance mechanism of resistance genes.The late blight resistance gene R3a from potato and Avr3a from P.infestans are R-Avr gene pairs which are in accordance with "gene to gene hypothesis".Therefore,the model plant tomato was used to construct the transgenic plant MM-R3a-Avr3a,which contained the late blight resistance gene R3a and DEX induced avirulence gene Avr3a.We use these transgenic plants as materials.We determinated and analyzed chlorophyll fluorescence parameters,antioxidant enzyme activity and ethylene content of transgenic plants in the process of HR.And we analyzed gene expression in the process of interaction between R3a and Avr3a induced by DEX,and identified some candidate genes involved in R-Avr interaction by VIGS.The results preliminarily analyzed mechanism of R3a-Avr3a interaction.The main conclusions of this study are as follows:1?Compared with MM-Avr3a,the chlorophyll fluorescence parameters(F0,Fv,Fm,QY-max)of MM-R3a-Avr3a plants showed a significant decrease at Oh,2h,4h,6h,and 8h.After DEX treatment,the activities of antioxidant enzymes in the leaves of MM-R3a-Avr3a tomato plants,such as MDA,SOD,POD,and CAT,all showed significant changes,peaking within 2h-6h.The results indicated that antioxidant enzymes were involved in the R3a-Avr3a interaction.Through the determination of the ethylene content and ethylene synthesis inhibitor(AVG)treatment during the HR process,the results showed that ethylene was involved in the HR of the interaction between R3a and Avr3a.2?Transcriptome technology was used to analyze the HR process of R3a and Avr3a interaction.GO analysis showed that the differential genes were mainly enriched in the pathways such as extracellular region,cell,transcription factor activity and so on.Through KEGG analysis,we found that in the early stage of R3a and Avr3a interaction,it was mainly enriched in the pathways of Plant-pathogen interaction,Plant hormone signal transduction,Glutathione metabolism,and in the later stage of R3a and Avr3a interaction,it was mainly enriched in Photosynthesis-antenna proteins,Carbon metabolism and other channels.The related genes of salicylic acid,jasmonic acid and ethylene are up-regulated during the interaction of and some disease-related genes such as RBOH,CNGC,CML,ERF,WRKY have been identified.Transcriptome analysis showed that the interaction between R3a and Avr3a is involved in multiple disease resistance pathways.3?Finally,the study screened the differential genes in the transcriptome data and verified the functions of some genes that may be involved in HR.A total of 10 VIGS vectors of differentially expressed genes were constructed,including WRKY22,ERF,CNGC,and ERF68.The results were verified on the MM-R3a-Avr3a,and the results showed that the silencing these 10 genes respectively did not block the occurrence of plant hypersensitive necrosis.Therefore,the experiment needs to further verify more differential genes in order to have a deeper understanding of the interaction mechanism between disease-resistant genes and avirulence genes.