Immune Genes Identification And Evolutionary Analysis Of Yellow Peach Moth(Lepidoptera:Crambidae) Based On Genomics

The yellow peach moth（Conogethes punctiferalis）is an important polyphagous agricultural pest distributed in East and South Asia.It mainly harms field crops and cash crops.Due to its boring habits,it is extremely difficult to prevent and control,resulting in huge economic losses every year.Previous studies on the biological character of yellow peach moths have found that they are not easily infected by pathogens in the field and can survive well in decayed plant fruits.Due to these characteristics,it is extremely difficult to use pathogenic fungi for control.However,for insect immunology research,yellow peach moths are an ideal research material.Because the research on the innate immune molecular mechanism and genomics of the yellow peach moth is extremely scarce,this paper analyzes the evolutionary characteristics of the immune gene of the yellow peach moth from three levels of pathogen recognition,immune signal transduction and immune effector molecules by integrating genomics,comparative genomics,population genetics,transcriptome and experimental means.The main results are as follows:（1）High quality genome map and resequencing analysis of yellow peach moth.This study,for the first time,utilized Hi Fi data from third generation Pacbio and combined with Hi-C assisted assembly technology to assemble the reference genome of yellow peach moth at the chromosome level.The genome size was 494Mb,with a scaffold N50 of 17.97Mb.BUSCO evaluated the integrity of the genome to be greater than 96%,with 21666 coding genes,GC content was 39.5%,and the repeat sequence proportion was 46%,Among them,the proportion of LINEs transposons is the highest（16.95%）.At the same time,for the first time,the entire genome of 110 individuals of the yellow peach moth in the north and south of China were re-sequenced,and a total of 5.8 million high-quality SNPs were detected.Most of the mutations occurred in non-coding regions.Principal component analysis,population structure,and F_STresults showed that there was no significant geographical differentiation of the yellow peach moth population in China.There is a certain degree of selective sweep of genes related to humoral immunity,cellular immunity,and neural signal transduction in the entire population.（2）Comparative Genome and Phylogenetic Evolution Analysis of yellow peach moth.Based on 1213single copy orthologous genes from 14 species,the phylogenetic relationship between the yellow peach moth and other Lepidoptera insects was reconstructed.The results showed that the yellow peach moth had the closest genetic relationship with the Asian corn borer,with a differentiation time of about 47million years,and a total of 10238 orthogroups.Compared with its ancestors,the yellow peach moth has1834 gene family expanded,including detoxification metabolism and chemosensory genes,pathogen recognition and immune signal transduction genes related to host adaptation.In addition,LTR,LINE transposons,and a small amount of DNA transposons also exhibit expansion,and the insertion of certain transposons can enhance antiviral ability.The collinearity analysis results show that the yellow peach moth has a good collinearity relationship with two other Crambidae species,the C.medinalis and the Ch.suppressalis,and 304 and 413 collinearity blocks have been identified respectively.（3）Immune recognition genes.A total of 5 PGRPs and 3 PGRPs were identified in the genome of the yellow peach mothβGRPs,2 TEPs,35 CTLs,and other diverse recognition receptors.Compared with other immune model insects,the number of CTLs in the yellow peach moth is significantly higher.It was further found that the increase in CTL quantity is due to the expansion of the CTL subfamily IML,reflecting the species specificity of the immune recognition gene evolution of the yellow peach moth.Multiple CTL genes were detected to have high expression levels during the infection of yellow peach moth by M.rileyi.Population genetics showed that the nucleotide polymorphisms of CTL-20 and thioseter-3 genes were significantly lower than the average level of the whole genome.（4）Immune signaling pathways.The yellow peach moth comprises a complete Toll pathway,IMD pathway and JAK/STAT pathway,in which the Toll protein of the Toll pathway has an obvious expansion of the gene family.In addition,by comparing with other insects of the family Crambidae or Pyralidae,it was found that the Dorsal gene responsible for positive regulation of antimicrobial peptide production in the Toll pathway of the peach moth moth and the Caspar gene responsible for negative regulation of antimicrobial peptide production in the IMD pathway exhibit a positive selection phenomenon.At the same time,the transcriptome experiment showed that the expanded gene family members and some genes in the immune signal pathway could respond to the infection of M.rileyi.The MODSP gene and Tr CP gene of the Toll pathway,as well as the STAT5B gene of the JAK-STAT pathway,exhibit selective sweeps.（5）Immune effector molecules,negative regulation,and horizontal transfer.The genome of the yellow peach moth moth contains a variety of effector molecules such as different types of antimicrobial peptides,lysozymes,and phenoloxidase proenzymes.Among them,Alo-2 antimicrobial peptide gene belonging to defensin has expansion,and evolutionary analysis shows that the production of this gene cluster may be due to horizontal transfer.The experiments showed that some antimicrobial peptide genes in the gene cluster had good antibacterial ability,and were selected in the evolution process.At the same time,the serine protease inhibitor genes responsible for negative regulation of immune effector molecules in the yellow peach moth had expanded.