Effect Of Different Treatments On The Organic Acids Metabolizing Enzymes And Related Genes Expression In Post-harvest Huangguan Pear Fruit

In this research, Huangguan pear after harvested was treated by0.2%chitosanand2%calcium chloride. The paper focused on the effect of different treatments onmalic acid and citric acid metabolism in Huangguan pear peel and pulp during storage.The contents of citrate acid and malic acid and their relative enzyme activities of pearfruit were assayed, then the relative expression of8organic acid metabolism-relatedgenes were analysed by real-time quantitative PCR The key enzymes of pear afterharvested citrate acid and malic acid metabolism were determined. It provided thebasis for the further elaboration of mechanisms of organic acid metabolism in pearafter harvested.(1) Research of the effect of different treatments on organic acid metabolism andactivities of related enzymes showed that0.2%chitosan and2%calcium chloridetreatments delayed titratable acid、malic acid and citrate acid activities of relatedmetabolism-enzymes decreasing on significant level（P＜0.05） or highly significantlevel（P＜0.01）, comprehensive analysis of all physical and chemical indicators.(2) The study on three related enzymes of malic acid which were PEPC,NAD-MDH and NADP-ME showed that the activity of NAD-MDH was the highest.The correlation between malic acid content and the activity of NAD-MDH and PEPCreaches significant level in different tissues.They play a very important role inaccumulating malic acid. The correlation between the activity of NADP-ME andmalic acid content was negative and the correlation reached significant level in pulp.There is no significant relativity between the activity of PEPC and malic acid contentin various treatments. The experimental results demonstrated that NAD-MDH andNADP-ME were the key enzymes which regulate the malic acid in Huangguan pearfruit after harvested.To citric acid metabolism of postharvest Huangguan pear, CS,PEPC and cyt-ACO are key enzymes. CS significantly affected the citric acid contentin peel and pulp in postharvest pear, while PEPC and cyt-ACO only remarkablyimpacted the citric acid content in pulp. Mit-ACO and citric acid content wasnegatively correlated, and NADP-IDH and citric acid content showed a positivecorrelation, however, both of them didn’t reached significant levels.(3) By the Real-time qPCR analysis of the malate dehydrogenase(Mdh) gene and malic enzyme(ME)gene，it was found that there were a positive correlation betweenthe two genes and the NAD-MDH or NADP-ME and there were also a significant orhighly significant correlation between the two genes and the malic acid content.By theReal-time qPCR amplification of CS, NADP-IDH and cyt-ACO, the results showedthat the NADP-IDH gene only had got a significant correlation with isocitratedehydrogenase activity in the peel, cyACO gene and cytoplasmic aconitase activity inthe peel and pulp significant correlated, but only had an important role in the contentof citric acid of the pulp.(4) Proton pump gene vVAtp1and malic acid content had significant or highlysignificant correlation, and the correlation reached-0.903**. There was a prominentnegative correlation between vVpp gene and accumulation of malic acid in the peels，but there was no obvious relationship between vVAtp2gene and malic acid content.vVAtp1, vVAtp2and vVpp genes didn’t have effect on citric acid content, and all ofthem overally showed a negative correlation. After the treatment of calcium chlorideand chitosan, the three pump genes’regulation on citric acid of the peel had differentlychanged.Comprehensive analysis of organic acid metabolism, calcium chloride and chitosancoating can affect gene transcription and expression levels in order to maintain a goodquality of pear fruit during storage, and has a better application prospects.