Genome-Wide Identification Of PpPAO And PpCuPAO Genes Family In Peach And Expression Analyis During Fruit Development And Ripening

Since peach is a typical fruit of respiratory morphosis,the fruit quickly enters the peak of breath after harvest,is extremely perishable at room temperature,and is not resistant to storage,seriously affecting the quality of peach products,making Peach's The economic value is greatly reduced.Polyamine is a type of growth regulator commonly found in higher plants.It is widely involved in plant growth and development,fruit maturation,and biological and abiotic stress.The content of polyamines in the early stage of fruit development is relatively high.With the fruit ripening,the content of polyamines rapidly decreases.Studies have shown that polyamine decomposition plays an important role in fruit maturation.Polyamine catabolism is mainly catalyzed by two types of enzymes,copper oxidase(CuAO)and polyamine oxidase(PAO).At present,there is no relevant research report on CuAO and PAO in peach.In this study,'Yellow Spring Honey' peach was used as the experimental material.The fruit growth curve was first mapped by measuring the diameter change during fruit development.Then selected the critical period of fruit maturation,treated with exogenous spermidine(Spd)and polyamine decomposition inhibitor(AG),and measured the fruit hardness,soluble solids,endogenous ethylene and auxin contents under different treatments.Physiological indicators showed that Spd and AG treatment can significantly delay peach fruit ripening.Subsequently,the transcriptome sequencing technology was used to analyze the expression changes of the genes related to mature softening of peach fruit,and the mechanism of the decomposition of polyamines in peach fruit ripening was analyzed.At the same time,the PpCuAO and PpPAO gene family members of Peach peach were excavated using information of the released peach genome database,and basic information such as their evolutionary relationship,gene structure,and chromosome distribution were analyzed using informatics.At the same time,the expression of PpCuAO and PpPAO genes in different tissues and organs was analyzed.The expression of PpCuAO and PpPAO genes in peach fruit growth and maturation were analyzed,and the key gene for polyamine decomposition during peach fruit ripening was screened out,which lays the foundation for the further development of polyamine decomposition in peach fruit maturation.The main findings are as follows:1.Effect of polyamine catabolism inhibitor treatment on peach fruit ripening.The fruit growth curve of 'Huang Shui Mi' showed a typical double "S" curve(S1,S2,S3,and S4).During the S3 period of fruit development,treated with 2 m M Spd,1 and 5 m M AG revealed that both Spd and AG treatment significantly delayed fruit ripening.Peach fruit firmness under Spd and AG treatment at S3 and S4 stage was significantly higher than the control level.However,soluble solids content determination showed that there was no obvious difference among control,Spd and AG treatment.At the same time,ethylene release assay showed that the release of ethylene under Spd and AG treatment was significantly lower than that of the control level.In addition,the determination of auxin(IAA)content showed that the levels of IAA in fruits treated with Spd and AG were significantly higher than control level,especially under Spd treatment.At the same time,the expression levels of genes involved in ethylene and auxin synthesis,signal transduction and cell wall degradation were analyzed.The results indicated that polyamine decomposition can participate in fruit maturation regulation by affecting ethylene,auxin and cell wall degradation.2.PpPAO gene identification and expression analysis in peach.Four PAO candidate genes,PpPAO1-PpPAO4,were found in peach genome.Based on genetic relationship analysis,PpPAO genes can be divided into four groups.The expression level of PpPAO gene in root was higher than that in flower,young leaves and old leaves.PpPAO gene expression was also induced by exogenous polyamine treatment.According to its expression pattern,it was speculated that PpPAO1 and PpPAO4 genes may be involved in polyamine terminal catabolism,while the remaining PpPAO2 and PpPAO3 genes may be involved in polyamine recovery response metabolism.Expression analysis during fruit development and maturation revealed that PpPAO1-3 basically up-regulated the expression,especially PpPAO1 was up-regulated,and PpPAO4 gene was down-regulated during the entire process.Peach PpCuAO gene mining and expression analysis.Four peach CuAO candidate genes(named PpCuAO1-PpCuAO4)were obtained through search and comparison and they were located on two chromosomes.The coding region size ranged from 1389 bp to 2328 bp.The isoelectric point and relative molecular weight predicted results showed that the isoelectric point of peach CuAO protein ranged from 6.11 to 8.77 and the relative molecular weight was from 52.1 to 82.8 k Da.Phylogenetic analysis showed that members of the PpCuAO gene family can be divided into two categories.PpCuAO possesses highly conserved 33 amino acid residues of plant CuAO and contains C-terminal or N-terminal signal peptide sequences.Tissue-specific expression analysis revealed that PpCuAO1 and PpCuAO2 were highly expressed in roots,and PpCuAO1 and PpCuAO2 were lower expressed in flowers.Expression analysis during fruit development and maturation revealed that only PpCuAO2 gene expression increased significantly during the S2-S3 period and then decreased rapidly.PpCuAO1,PpCuAO3,and PpCuAO4 all showed down-regulation during the whole process,while PpCuAO3 and PpCuAO4 showed a significant increase during S4.