Zhang Yingzi, Jin Jiajing, Zhu Shenchao, Sun Quan, Zhang Yin, Xie Zongzhou, Ye Junli, Deng Xiuxin
Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China.
Hortic Res. 2022 Dec 30;10(3):uhac290. doi: 10.1093/hr/uhac290. eCollection 2023 Mar.
As an essential horticultural crop, has carotenoid diversity, which affects its aesthetic and nutritional values. ,-Xanthophylls are the primary carotenoids accumulated in citrus fruits, and non-heme di-iron carotene hydroxylase (BCH) enzymes are mainly responsible for ,-xanthophyll synthesis. Previous studies have focused on the hydroxylation of , but the role of its paralogous gene in citrus, , remains largely unknown. In this study, we revealed the β-hydroxylation activity of citrus BCH2 (CsBCH2) for the first time through the functional complementation assay using , although CsBCH2 exhibited a lower activity in hydroxylating -carotene into -cryptoxanthin than citrus BCH1 (CsBCH1). Our results showed that overexpression of in 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, and , and illustrated the backup compensatory role of for in citrus xanthophyll biosynthesis. The independent function of and its cooperative function with in -cryptoxanthin biosynthesis suggested the potential of to be employed for expanding the synthetic biology toolkit in carotenoid engineering.
作为一种重要的园艺作物，具有类胡萝卜素多样性，这会影响其美学和营养价值。β,β-叶黄素是柑橘类水果中积累的主要类胡萝卜素，非血红素二铁胡萝卜素羟化酶（BCH）主要负责β,β-叶黄素的合成。以往的研究主要集中在β-胡萝卜素的羟基化上，但其同源基因在柑橘中的作用，即CsBCH2，在很大程度上仍不清楚。在本研究中，我们首次通过使用β-胡萝卜素的功能互补试验揭示了柑橘BCH2（CsBCH2）的β-羟基化活性，尽管CsBCH2将β-胡萝卜素羟基化为β-隐黄质的活性低于柑橘BCH1（CsBCH1）。我们的结果表明，在柑橘愈伤组织中过表达CsBCH2会增加叶黄素比例和质体小球大小，并对类胡萝卜素生成基因表达进行反馈调节。本研究揭示了两个同源基因CsBCH1和CsBCH2不同的表达模式和功能特征，并阐明了CsBCH2在柑橘叶黄素生物合成中对CsBCH1的备用补偿作用。CsBCH2的独立功能及其在β-隐黄质生物合成中与CsBCH1的协同功能表明，CsBCH2有潜力用于扩展类胡萝卜素工程中的合成生物学工具包。
