Light regulates ascorbic acid accumulation and ascorbic acid-related genes expression in the peel of eggplant

Ascorbic acid (AsA) is one of the important metabolites and beneficial to human health. First of all, we found the phenomenon that light could promote AsA accumulation in the peel of eggplant. To further understand the regulatory mechanism of light on the formation of AsA in fruits, we isolated seven novel L-galactose pathway related genes (SmGMP, SmGME1, SmGME2, SmGGP, SmGPP, SmGalDH and SmGLDH) in AsA biosynthesis from eggplant. Correlation analysis suggested that AsA content showed significant positive correlation with the expression levels of SmGME2, SmGGP, SmGPP, SmGalDH and SmGLDH. There were many putative light responsive elements in all the seven promoters of genes, and the expression analysis confirmed that the seven genes were induced by light. Then we overexpressed the seven genes in Arabidopsis and observed that the AsA content were significantly increased in the leaves of transgenic plants. Moreover, the transgenic plants also displayed an increase in low temperature tolerance. The present study provides insight into light regulation of AsA biosynthesis in eggplant and may facilitate genetic engineering for improvement of the AsA content and stress tolerance in plants.