Regulation Of Peach Fruit Softening Based On Genome Re-sequencing And Transcriptome Data

Peach(Prunus persica L.Batsch),originated in China,is favored by consumers.It is widely distributed in the world and has a large variety of cultivars.Different types of peach fruits have different softening types,which can be divided into three categories: melting flesh peach,non-melting flesh peach and stony-hard peach.The melting flesh peach could soften rapidly after harvest,aggravating the fruit loss in storage and logistics.At present,the research on peach fruit softening is relatively limited and mainly focused on Pp PG1/2 which are the major genes responsible for melting/non-melting.In this study,GWAS and transcriptome analysis were carried out on 305 peach fruit harvesting points,and the post harvest time period of two melting flesh peach fruits treated with 1-MCP was taken as the line,to comprehensively explore the regulating genes of peach fruit firmness and softening and the underlying molecular mechanism.The main results are as follows:1.There were 13 SNP sites significantly related to the firmness value.Based on the SNP data of population re-sequencing and the characteristics of genetic structure,combined with 305 peach fruit firmness data collected in two years,the genome-wide association analysis was carried out,13 SNP loci significantly related to the firmness value were screened,and the chromosome fragments linked to each SNP locus were obtained using the principle of genetic linkage imbalance.There were 50 genes in the significant fragments,which had a certain correlation with the firmness of peach fruit,as candidate genes for regulating fruit firmness.2.Pp LRR-RLK and Pp Gal Ox may be involved in the regulation of peach fruit firmness.Through the statistics and analysis of SNP sites in the gene,it was found that there were non synonymous SNP sites in Pp LRR-RLK and Pp Gal Ox,and different genotypes of this site corresponded to different firmness ranges,and there were significant differences in phenotypes among different genotypes.3.A new gene Pp PG24 related to peach fruit softening was identified.1-MCP treatment of soluble peaches can effectively slow down the softening process.Through post harvest transcriptome analysis,WGCNA and correlation analysis,four cell wall modification genes(Pp PG1,Pp PG2,Pp PG24,Pp PMEI)related to peach fruit softening were obtained.4.Pp HDZIP is the transcriptional activator of Pp PG1 and Pp PG2.A transcription regulation network for peach fruit softening was constructed and the expression of two transcription factors Pp HDZIP and Pp MYB were highly correlated with hardness and the gene expression of three cell wall metabolic enzyme genes(Pp PG1,Pp PG2,Pp PMEI).The tobacco double luciferase experiment showed that Pp HDZIP had a significant activation effect on the promoters of Pp PG1 and Pp PG2.To sum up,this study obtained the key genes Pp LRR-RLK,Pp Gal Ox,Pp PG1/2/24,Pp PMEI and regulatory factors Pp HDZIP,Pp MYB for peach fruit softening by GWAS and postharvest transcriptome analysis,among which Pp LRR-RLK,Pp Gal Ox,Pp PG24,Pp HDZIP and Pp MYB were first reported;The study confirmed that Pp HDZIP is the transcriptional activator of Pp PG1 and Pp PG2 and added new nodes and contents to the regulation network of peach fruit softening genes.