Mining Candidate Genes For Brown Spot Resistance In The Sugar Beet NBS Gene Family Based On Transcriptomics

Cercospora leaf spot severely restricts sugar beet growth,and the NBS-LRR family is the largest disease resistance gene family in plants.In this study,bioinformatics was used to identify the NBS-LRR gene family in the whole genome of sugar beet.Transcriptome sequencing and plant endogenous hormone concentration were carried out for varieties with high resistance to Cercospora leaf spot and high susceptibility to Cercospora leaf spot at the initial stage and onset of Cercospora beticola Sacc.infection.The resistant genes to Cercospora leaf spot were excavated through three aspects of separate research and joint analysis,it provides a theoretical basis for revealing the disease-resistance mechanism in sugar beet.The main results are as follows:1.There are 267 NBS-LRR genes in the sugar beet genome,belong to five subfamilies: N-type,NL type,CNL type,TNL type,and RNL type,and most of them are located on chromosomes 2,3,4,and 7.73.25% of the genes cluster into 27 gene clusters.Sugar beet CNL subfamily lacks RNBS-C conserved motif,and PLN03210 and PLN0013 domains appear on large scale.Promoters of sugar beet NBS-LRR genes contain many cis-elements related to plant hormones,low-temperature stress,anaerobic induction,and wound response.Genes in the CNL and RNL subfamilies have the highest homology to disease resistance proteins in quinoa,followed by spinach disease resistance proteins.2.There were more differentially expressed genes and NBS differentially expressed genes in the highly susceptible varieties than in the highly resistant varieties,and the onset of disease was more frequent than at the beginning of infestation.In the KEGG annotations,the most significant pathway enriched in the early stage of infection of highly resistant varieties and highly susceptible varieties was plant-pathogen interaction.The phenylpropane biosynthesis pathway was the most enriched pathway in the two varieties at the onset.NBS-LRR genes were only involved in the plant pathogen interaction pathway.The gene module with the greatest correlation with Cercospora leaf spot was obtained by Weighted Gene Co-expression Network Analysis,including 2427 genes,of which 39 belong to NBS-LRR family.3.The concentration of salicylic acid in the highly resistant varieties increased from the control group to the initial stage of infection,and decreased from the initial stage of infection to the onset.The concentration of jasmonic acid in the highly resistant varieties increased from the control group to the initial stage of infection,and decreased from the initial stage of infection to the onset.In highly susceptible varieties,the concentration of salicylic acid decreased from the control group to the initial stage of infection,and increased from the initial stage of infection to the onset stage.The concentration of jasmonic acid increased from the control group to the initial stage of infection,and decreased from the initial stage of infection to the onset.One salicylic acid signal transduction pathway-related gene was identified as PR1 protein in the highly resistant variety,and two were identified in the highly susceptible variety.Two jasmonic acid signaling pathway-related genes were screened in the highly resistant varieties,and their encoded proteins were identified as JAZ protein and MYC2 transcription factor.five were identified in the highly susceptible varieties.