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Ascorbic acid (AsA) is an important antioxidant in plants and an essential vitamin for humans. Extending the study of AsA-related genes from Arabidopsis thaliana to Brassica rapa could she dlight on the evolution of AsA in plants and inform crop breeding. In this study,we conducted whole - genomeannotation, molecular-evolution and gene - expression analyses of all known AsA - relatedgenes in B. rapa. The nucleobase – ascorbate transporter (NAT) gene family and AsA L- galactose path way genes were also compared among plant species. Four important insights gained are that :1)102 AsA - related gene were identified in B. rapa and they mainly diverged 12– 18 Ma accompanied by the Brassica-specific genome triplication event; 2) during their evolution, these AsA-related genes were preferentially retained, consistent with the gene dosage hypothesis; 3) the putative proteins were highly conserved, but their expression patterns varied ; and 4) although the number of AsA - related genesis higher in B.rapa thanin A. thaliana, the AsA contents and the numbers of expressed genes in leaves of both species are similar, the genes that are not generally expressed may serve as substitutes during emergencies. In summary, this study provides genome-wide insights in to evolutionary history and mechanisms of AsA - related genes following whole-genome triplication in B. rapa
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