Expression profiles of genes and enzymes related to ascorbic acid metabolism in fruits of Ziziphus jujuba Mill. ‘Jinsixiaozao’

The fruit of Chinese jujube (Ziziphus jujuba) possesses extremely high concentrations of ascorbic acid (AsA). The accumulation of AsA, the expression patterns of the nine genes related to AsA metabolism as well as the activities of five enzymes involved in AsA synthesis, oxidation and recycling were investigated during fruit development in Z. jujuba Mill. 'Jinsixiaozao'. The results showed that the high level of AsA accumulation in jujube fruit is due to a contribution from both AsA biosynthesis and AsA recycling. It is suggested that L-galactono-1,4lactone dehydrogenase, ascorbate peroxidase and monodehydro-ascorbate reductase are the crucial genes/ enzymes of jujube AsA synthesis, oxidization and recycling, respectively. These results provide useful new insights into the regulatory mechanisms of AsA accumulation in Chinese jujube.