Studies On Characterization Of Organic Acids Matebolism And Expression Of Relative Genes During Fruit Development Of ‘Ganmi6’

Actinidia eriantha is endemic to China.It attracted the attention of researchers because of its high AsA content and good peeling performance.Up to now,studies on characteristics of high acid and low sugar,and organic acid metabolism relative genes cloning and expression of A.eriantha has not been reported.‘Ganmi 6’ was taken as experimental material in this study,the components and content of sugars and organic acids in fruit of ‘Ganmi 6’ were determined during fruit development with HPLC.The activities of organic acid metabolism-related enzymes were analyzed by using the method of ultraviolet spectrophotometry,and the relative expression of major organic acid metabolizing enzymes genes in the fruit development of ‘Ganmi 6’ was detected and analyzed by qRT-PCR.The main results were as follows:Fructose,glucose and sucrose were the main sugar components during the fruit development of ‘Ganmi 6’,and the sugar content was the highest at soft ripening.Fructose content was 31.25 mg/g,glucose content was 27.21 mg/g,sucrose content was 17.80 mg/g,fructose and glucose accounted for 41.0% and 35.7% of the total sugar content.In this experiment,AsA and 8 kinds of organic acids were detected during the fruit development of ‘Ganmi 6’.The order of organic acid content in the fruit of ‘Ganmi 6’ during soft ripening period was: quinic acid > citric acid > malic acid > lactic acid > succinic acid >oxalic acid > tartaric acid > fumaric acid.Quinic acid,citric acid and malic acid were higher in the whole development period,accounting for 42.0-69.2%,2.0-63.6% and4.2-32.2% of the total acid respectively.These three acids accounted for 75.4-91.0% of the total acid,Through correlation analysis,it was found that there was a significant correlation between quinic acid and total acid,with a correlation coefficient of 0.88.The quinic acid was the dominant acid of ‘Ganmi 6’.The trend of the activity of NADP-SDH was similar to that of quinic acid during fruit development of ‘Ganmi 6’,and the trend were decreased during early fruit development.The trend of activities of CS,NAD-IDH,PEPC were similar to that of citric acid content,showing a trend of increased during early fruit development and then decreased.The trend of the activity of NAD-MDH was similar to that of malic acid,showing a trend of increased during early fruit development and then remained stable.The correlation analysis showed that the content of quinic acid was significantly correlated with the activity of NADP-QDH,with a correlation coefficient of 0.60,and a significant negative correlation with NAD-IDH,with a correlation coefficient of-0.62.There was extremely significant positive correlation between citric acid and the activity of NAD-MDH,the correlation coefficients was 0.72,which was significantly positively correlated with the activity ofPEPC,CS,and NAD-IDH,the correlation coefficients were 0.58,0.60,and 0.57,and NADP-QDH and NADP-SDH showed a significant negative correlation with citric acid,the correlation coefficients were-0.66,-0.67.Malic acid was significantly correlated with the activity of NAD-MDH,with a correlation coefficient of 0.61,which was significantly negatively correlated with that of NADP-SDH with a correlation coefficient of-0.59.The main organic acid components was not correlated with the activity of NADP-ME and ACO.This study suggests that the activiyies of NAD-IDH,CS,NADP-QDH,NADP-SDH,NAD-MDH,and PEPC play an important role in the organic acid metabolism during the development of ‘Ganmi 6’,while NADP-ME and ACO have little influence on it during the whole stage.During the fruit development of ‘Ganmi 6’,the SDH gene was consistent with NADP-QDH and NADP-SDH activity,and reached a high level in the early development stage.The relative expression of IDH gene was similar to the activity of NAD-IDH,which increased first and then decreased.The relative expression of ACO gene and the activity of Mit-ACO were familiar with each other,but it has quite different with citric acid content,and reached the maximum when after flowering 140-155 d.Correlation analysis showed that SDH gene was significantly correlated with the activity of NADP-QDH and NADP-SDH during fruit development,and the correlation coefficients were 0.79 and 0.91.IDH gene and NAD-IDH showed significant correlation and the correlation coefficients was 0.88.ACO gene is highly correlated with Mit-ACO expression and the correlation coefficients was 0.69,but both of them have no correlation with citric acid.There was no significant correlation between CS and DQS genes with quinic acid,citric acid and related enzymes.This study believes that most of the organic acid metabolizing enzyme activities are regulated by their corresponding genes at the transcriptional level,and some genes(CS,DQS)may be affected by post-translational modification,and their activity is not regulated by genes at transcriptional level.