Characterization of genes involved in pear ascorbic acid metabolism and their response to bagging treatment during 'Yali' fruit development

In this study, a total of 59 genes involved in ascorbic acid (AsA) metabolism were identified from pear genome with diverse chromosome locations, gene structures, and cis-acting elements. Most were derived from WGD/ segmental duplication blocks, and purifying selection was the main driving force for their expansion. Their expression profiles were tissue-specific, and postharvest light treatment would alter their expression profiles. During 'Yali' pear development, in association with visual and inner quality change, AsA, dehydroascorbate (DHA) and total AsA (T-AsA) concentrations decreased in association with the downregulated activities of glutathione oxidoreductase (GR), L-galactono-1, 4-lactone dehydrogenase (GalLDH), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and ascorbate oxidase (AO) as well as various expression patterns of 59 genes in their metabolic pathway. Bagging treatment obviously suppressed AsA and T-AsA concentrations in both pericarp and cortex, which accompanied with the downregulated GalLDH, GR, MDHAR, and APX activities and the upregulated AO activity. Furthermore, the expression profiles of several genes in the pericarp and cortex were altered after bagging. In combination of the results from quality, physiological-biochemical and gene expression assay, several genes were proposedly responsible for bagginginduced reduction of AsA and T-AsA concentrations in the pericarp and cortex.