Research On Physiological And Molecular Mechanism Of AsA Accumulation In Jujube And Wild Jujube

Ascorbic acid(AsA)is also called vitamin C,is an essential metabolite in plants and animals,and is also an indispensablel substance for human normal growth.However,AsA can't be synthesized directly by hummans,thus,humans have to ingest from the outside world.Fruits and vegetables are the main source of AsA for humans.Jujube(Ziziphus jujuba Mill.)and wild jujube(Ziziphus acidojujuba Cheng et Liu)are the plants of Ziziphus Mill of Rhamnaceae and friuts are rich of Vc,which have the reputation of “natural vitamin pill”.In this experiment,fresh Jujube Cultivars(‘Zhanshanmizao 1',‘Zhanshanpinguozao' and ‘Luojiangtiaoyuanzao')and wild jujube(‘Yuanxingxiaosuanzao')were used as test materials.The metabolic mechanism of AsA during the development of jujube and wild jujube was studied from the morphological,physiological and molecular levels.The main results were as follows:1.The fruits of jujube and wild jujube have the highest content of AsA.The contents of AsA and T-AsA in jujube and wild jujube both rised firsty and then descended,and AsA was mainly accumulated in enlargement friut.The content of AsA in leavesrised firsty and then descended,the content of AsA was the lowest in young leaves,and the content of DHA in leaves was always higher than AsA.2.The content of soluble sugar of fruit during the development of jujube and wild jujube showed the same tend of "rised-droped-rised",and the content of titratable acid first descended and then riseed.There was no significant correlation between the content of AsA and the content of soluble sugar in the fruit of jujube and wild jujube,but it has a negative correlation with the content of titratable acid and has a positive correlation with the sugar-acid ratio.3.The activity changes of different metabolic enzymes in the friut during the development of jujube and wild jujube are different.But only the activity changes of GalDH was similar to that of AsA in the fruit of ‘Zhanshanmizao 1',the activity changes of GalLDH was correlated with that of AsA in the fruit of‘Luojiangtiaoyuanzao' and‘Yuanxingxiaosuanzao'.There was no significant correlation between the activity changes of AsA metabolism enzyme and the changes of AsA content in the leaves.4.Real-time PCR analysis showed:The synthetic pathways of AsA in the friuts of jujube and wild jujube included L-galactose pathway and inositol pathway,and GDP-mannose-3',5'-epimerase 1 gene(GME1),GDP-mannose pyrophosphorylase 1 gene(GMP1),GDP-L-galactose-1-phosphate phosphorylase gene(GGP),L-Galactose-1-phosphate phosphatase gene(GPP),L-galactono-dehydrogenase gene(GalDH),L-galactono-1,4-lactone dehydrogenase gene(GalLDH)and Inositol oxygenase 1 gene(MIOX1)may be the key genes in the friut of fresh jujube and wild jujube in the South.In addition,GME,GMP and GalDH may play a key role in the synthesis of AsA in the leaves of jujube and wild jujube.In the recycling pathway,Monodehy droascorbate reductase gene(MDHAR)and Dehydroaseorbate reductase gene(DHAR)co regulate the regeneration of AsA in the fruit and leaves of jujube and wild jujube.In a conclusion,there are significant differences in AsA content in different tissues of jujube and wild jujube,AsAs synthesis,degradation and regeneration pathways influences the accumulation of AsA,Synthetic pathways of AsA in jujube and wild jujube fruit include L-galactose pathway and inositol pathway,GME1,GMP1 and GGP might be the key genes of AsA synthesis in fresh jujube friuts and higher expression of GME1,GMP1,GGP,GPP,MIOX1,as well as the recycling genes MDHAR and DHAR might be the reasons for the higher AsA content in ‘Yuanxingxiaosuanzao' fruits.GME?GMP and GalDH might be the key genes of AsA synthesis in fresh jujube leaves.