부산대학교 도서관

As an essential horticultural crop, Citrushas carotenoid diversity, which affects its aesthetic and nutritional values. ß,ß-Xanthophylls are the primary carotenoids accumulated in citrus fruits, and non-heme di-iron carotene hydroxylase (BCH) enzymes are mainly responsible for ß,ß-xanthophyll synthesis. Previous studies have focused on the hydroxylation of BCH1, but the role of its paralogous gene in citrus, BCH2, remains largely unknown. In this study, we revealed the ß-hydroxylation activity of citrus BCH2 (CsBCH2) for the first time through the functional complementation assay using Escherichia coli, although CsBCH2 exhibited a lower activity in hydroxylating ß-carotene into ß-cryptoxanthin than citrus BCH1 (CsBCH1). Our results showed that overexpression of CsBCH2in citrus callus increased xanthophyll proportion and plastoglobule size with feedback regulation of carotenogenic gene expression. This study revealed the distinct expression patterns and functional characteristics of two paralogous genes, CsBCH1and CsBCH2, and illustrated the backup compensatory role of CsBCH2for CsBCH1in citrus xanthophyll biosynthesis. The independent function of CsBCH2and its cooperative function with CsBCH1inß-cryptoxanthin biosynthesis suggested the potential of CsBCH2to be employed for expanding the synthetic biology toolkit in carotenoid engineering.