Transcriptome Analysis And Resistance Related Gene Mining In Response To Ralstonia Solanacearum Infection In Peanut

Peanut(Arachis hypogaea L.)is an important source of edible oil and protein,and is one of the most important oil crops and economic crops in the world.China is a big country of peanut production,consumption and export.Peanut bacterial wilt caused by Ralstonia solanacearum is one of the most serious bacterial soil borne diseases in peanut production.At present,cultivating and planting resistant varieties is the most economical and effective prevention and control measures for environmental safety.However,the regulatory mechanism of peanut resistance to bacterial wilt and the molecular mechanism of peanut-bacterial blight interaction are still unclear.In the early stage,our team crossed the resistant variety yuanza9102 with the susceptible variety Xuzhou68-4 to construct a recombinant inbred line population,and found the main QTL qBWRB02.1 for disease resistance.In order to further analyze the molecular basis of resistance to bacterial wilt of Yuanza9102,In order to further analyze the molecular basis of resistance of Yuanza9102 to bacterial blight,this study used Yuanza9102 and Xuzhou68-4 as materials to perform artificial inoculation and simulated inoculation(water)treatment of bacterial wilt at the seedling stage,and took root tissues at 5 time points(12,24,48,72 and 96h)after inoculation for transcriptome sequencing analysis.The transcriptional responses of resistant and susceptible parents to bacterial wilt were compared and analyzed.The types,chromosomal distribution and expression of peanut resistance genes were analyzed at the genome-wide level,with emphasis on the candidate genes in the QTL region of the main resistance to bacterial wilt.The main findings are as follows:1.The death rates of Yuanza9102 and Xuzhou68-4 inoculated with bacterial wilt were 20% and100%,respectively.A total of 2,844 M clean reads were obtained by transcriptome sequencing,with a comparison rate of about 71%,and the number of expressed genes accounted for about 67% of all annotated genes.The results showed that 2192 genes were up-regulated and 2043 genes were down regulated by Ralstonia solanacearum at five time points,while 2153 and 2464 genes were up-regulated and down regulated by Ralstonia solanacearum in susceptible varieties.GO and KEGG enriched by differentially expressed genes in resistant and susceptible materials were different in category and number.421 genes were specifically differentially expressed after inoculation with R.solanacearum;The differential expression of 1893 genes between resistant and susceptible materials provided a basis for exploring genes related to bacterial wilt resistance at the transcriptional level.2.According to the plant disease resistance gene database,a total of 4156 candidate genes were identified in the whole genome of peanut.According to the conserved domain composition of disease resistance genes,they were divided into 15 categories,including 536,490,232,182 and 149 typical disease resistance genes RLK,RLP,NL,CNL and TNL,respectively.The distribution of disease resistance genes were uneven on chromosomes,and most of them were concentrated on chromosome B02.Transcriptome profiling showed that 111 genes were specifically expressed in resistant material,104 genes were specifically expressed in susceptible material,2216 genes were expressed in both resistant and susceptible materials while 1725 genes were not expressed in both resistant and susceptible materials.Two kinds of differentiate expressed R genes were identified,including five genes in the first group which were response to the infection of Ralstonia solanacearum at specific time and 65 genes in the second group which exhibited higher expressions in resistant cultivar than susceptible cultivar.3.There were 120 annotated genes in the candidate region of qBWRB02.1.Among them,10 genes were specifically differentially expressed after inoculation with R.solanacearum.The fluorescent quantitative primers for the unknown proteins Arahy.2ZXA1 E and Arahy.Z287 JL were designed and qRT-PCR showed that they were specifically up-regulated in Yuanza9102 at 12 h and 24 h after inoculation.In addition,12 differentially expressed genes were identified between resistant and susceptible materials.Primers of NBS resistance candidate gene Arahy.5D95 TJ were designed,qRT-PCR showed that the expression level of Yuanza9102 was higher than that of Xuzhou68-4,and its conservative structure was different from that of Ah RRS5(ZHANG et al.,2017).Therefore,Arahy.5D95 TJ was very likely to be a new peanut resistance gene,and its gene function needs further verification.This study will help to analyze the gene function of peanut response to bacterial wilt infection at the molecular level,excavate candidate genes related to disease resistance response,and provide available gene resources for peanut disease prevention and control and disease resistance breeding.