Mining Of Genes Related To Suture Softening Of Peach Fruit Through RNA-seq

Peach?Prunus persica?L.?Batsch?is one of the most important economic fruit trees in China.Some peach varieties have the phenomenon of early softening of suture during fruit ripening,which seriously affects the fruit quality and reduces the economic benefit.Beijing No.2 mutant matured about 15 days later than its wild type and showed early softening and red color changing in the area of fruit suture,so it is an excellent material for studying the mechanisation of suture softening.This study consists of three parts,and the main results are as follows:Thirty-one peach varieties?lines?in QinHuangdao area were investigated and classified according to the softening position of the suture.Three varieties with soft sutures were screened out from early,middle and late ripening peaches:Z1-2?line?,Chaoyue No.2 and YanHong,and the control varieties were ShuGuang,P2-1?line?and WanJiubao.The results of physiological indexes showed that in the soft varieties,the hardness at the suture was significantly lower than that of the fruit surface,while the ethylene kurtosis and anthocyanin content were significantly higher than those of the fruit surface.In the control varieties,there were no significant differences in ethylene kurtosis,anthocyanin content and hardness in suture and fruit surface.In six varieties,the content of soluble solids in suture was lower than that in fruit surface,and the change of ABA had no rule,which had no correlation with suture softening.At the late ripening stage,the anthocyanin content in the suture was higher than that in the fruit surface of Beijing No.2 late-maturing mutant;meanwhile,the hardness of the suture line was significantly lower than that of the fruit surface,and the ethylene peak was delayed,fruit softening of the mutant was delayed,too.Based on the Illumina HiSeq ^TM2500 high-throughput sequencing platform,transcriptomes of four samples?the suture of the Beijing No.2,the fruit surface of the Beijing No.2,the suture of the mutant,and the fruit surface of the mutant?were sequenced.Compared with the suture,a total of 1889 differential expressed genes?DEGs?were detected in the fruit surface of the mutant.The Kyoto Encyclopedia of Genes and Genomes?KEGG?pathway enrichment analysis showed that DEGs participating in the pathways of plant hormone signal transduction,biosynthesis of secondary metabolites,plant-pathogen interaction,phenylpropane biosynthesis and metabolic pathway were significantly enriched.According to the analysis of differential gene expression and the KEGG pathway enrichment,46 genes related to fruit suture softening and redness were screened,including 9 cell wall degradation-related genes?PG1,PL5,BGAL1,PME48,XTH33,STP13,SUS7,SS,and EXPA4?,13 plant hormone signal transduction pathway genes?ETR2,ACS1,ACO1,IAA7,IAA8,IAA29,AUX22,AUX28,GH3.1,ARF1,SAUR36,AHK4,and ARR3?,10 fruit color-related genes?PORA,HO1,CYP707A1,NCED1,LUT2,DFR,CHS2,CHI3,ANS,and F3H?,14transcription factors?3 MYB,1 NAC,2 ERF,3 BHLH,and 5 WRKY?.A PME gene related to fruit softening was cloned and named PpPME48?accession number:MT019687?.Bioinformatic analysis showed that the PpPME48protein encodes a total of 370 amino acids.The molecular weight of the protein is41187.06Ku,contains a pectin methylesterase domain and a N-terminal-PRO region,so PpPME48 belongs to Type II.Phylogenetic tree analysis showed that the amino acids sequence of PpPME48 was closely related to Prunus dulci,Prunus mume and Prunus avium.Real-time PCR analysis revealed that the expression of PpPME48gene in suture softening variety YanHong was higher than that in non-softening variety WanJiubao and the expression level in suture line was significantly higher than that in fruit surface,therefore the PpPME48 gene is a gene closely related to the softening of suture.