Research On The Accumulation Of Sugar And Organic Acid In Jujube Fruit

Sugar and acid are important factors that determine the flavor substance and quality of fruit.The study on the accumulation of sugar and acid in fruit and the expression of related genes are helpful to further regulate the metabolism of sugar and acid in jujube(Ziziphus jujuba Mill.)and to provide a theoretical basis for improving the quality and flavor of jujube fruit.In the present study,?Yuanxingxiaosuanzao?,?Luojiangtiaoyuanzao?,and“Shucuizao” were used as material.The accumulation of sugar and acid during the development of jujube and wild jujube(Ziziphus acidojujuba C.Y.Cheng et M.J.Liu)was studied from physiological and molecular aspects.The main results were as follows:1.The content of soluble sugar in fruit development of jujube and wild jujube showed the trend of “rise-drop-rise”.The titratable acid content of ?Yuanxingxiaosuanzao? and?Luojiangtiaoyuanzao? show the trend of “decreasing-rising-descending”.The titratable acid content of “Shucuizao” were cultivated in open field decreased at 20～55 days after anthesis.The titratable acid content of “Shucuizao” were cultivated in greenhouse had two small accumulation peaks at 48 d and 76 d after anthesis.2.The sugar and acid components and contents in jujube and wild jujube fruits were determined by HPLC method.It was found that that ?Yuanxingxiaosuanzao?,?Luojiangtiaoyuanzao? and “Shucuizao” are sucrose accumulation type.It can be seen from this that citric acid and malic acid were the main accumulated acid in?Yuanxingxiaosuanzao?,malic acid were the main accumulated acid in?Luojiangtiaoyuanzao? and “Shucuizao”.3.The results of q RT-PCR showed that Zj SS1,Zj SS3,Zj SPS1 and Zj SPS2 were key genes in sucrose synthesis of ?Yuanxingxiaosuanzao?,?Luojiangtiaoyuanzao? and“Shucuizao”.Zjv INV1,Zjv INV2,Zjn INV1 and Zjc INV3 were key genes of sucrose degradation,fructose and glucose synthesis of ?Yuanxingxiaosuanzao?.Zj HK3,Zj HK6 and UGP were key genes of fructose and glucose degradation in ?Luojiangtiaoyuanzao?and “Shucuizao”.The low expression of INV in ?Luojiangtiaoyuanzao? and “Shucuizao”inhibited the accumulation of fructose and glucose in fruit.4.The results of q RT-PCR showed that CS1 and Aco4 were key genes to regulate the synthesis and degradation of citric acid of ?Yuanxingxiaosuanzao?.CS1,CS3,Aco2-1 and Aco4 were key genes to regulate the synthesis and degradation of citric acid of?Luojiangtiaoyuanzao?.CS1,CS3 and Aco2-1 were key genes to regulate the contents of citric acid of “Shucuizao”.Therefore,the expression of CS and Aco were the cause of the significant difference in citric acid content between ?Yuanxingxiaosuanzao?,?Luojiangtiaoyuanzao? and “Shucuizao”.The synthesis and degradation of malic acid is the result of the co-regulation of MDH,PEPC,NADP-ME and FUM.In conclusion,sucrose were the main accumulated sugar in fruit development of jujube and wild jujube.The different flavor substance of ?Yuanxingxiaosuanzao?,?Luojiangtiaoyuanzao? and “Shucuizao” are mainly caused by the different contents of malic acid and citric acid.The sugar composition and content in jujube and wild jujube are determined by related synthetic genes and degrading genes,in which INV plays an important role.CS and Aco are important genes for controlling the organic acid composition and content of jujube and wild jujube fruit.