The halophilic green alga Dunaliella bardawil FACHB-847 is rich in lutein and α-carotene, which has great potential for carotenoid production in open ponds. In this study, genes encoding lycopene β- and ε-cyclases (DbLcyB and DbLcyE) from D. bardawil FACHB-847 were functionally identified by genetic complementation in E. coli. The bifunctional DbLcyB not only catalyzed the formation of both mono- and bi-cyclic β-rings with a major β-cyclase activity, but also possessed a weak ε-cyclase activity. In contrast, DbLcyE preferred to convert lycopene into monocyclic δ-carotene, and possessed a weak β-monocyclase activity. Lutein and α-carotene were the prominent carotenoids in D. bardawil FACHB-847, which was in agreement with the result of genetic complementation of co-expression of DbLcyB and DbLcyE in E. coli with α-carotene as the prominent product. The bifunctional DbLcyB and DbLcyE may contribute to the high accumulation of α-carotene in D. bardawil FACHB-847. Interestingly, the accumulation of lutein in D. bardawil FACHB-847 was more sensitive to salt stress, while the accumulation of β-carotene in D. salina CCAP 19/18 was induced by salt stress. In brief, the production of different carotenoid compositions from these two Dunaliella species can be induced by different growth conditions.

中文翻译：

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来自富含叶黄素的杜氏杜氏藻的番茄红素 β- 和 ε-环化酶的双功能鉴定

嗜盐绿藻Dunaliella bardawil FACHB-847富含叶黄素和α-胡萝卜素，在开放池塘中具有巨大的类胡萝卜素生产潜力。在这项研究中，编码来自 D. bardawil FACHB-847 的番茄红素 β-和 ε-环化酶（DbLcyB 和 DbLcyE）的基因通过大肠杆菌中的遗传互补进行了功能鉴定。双功能 DbLcyB 不仅催化形成具有主要 β-环化酶活性的单环和双环 β-环，而且还具有弱的 ε-环化酶活性。相比之下，DbLcyE 更倾向于将番茄红素转化为单环 δ-胡萝卜素，并且具有较弱的 β-单环化酶活性。叶黄素和 α-胡萝卜素是 D. bardawil FACHB-847 中的主要类胡萝卜素，这与 DbLcyB 和 DbLcyE 在大肠杆菌中以α-胡萝卜素为主要产物的共表达的遗传互补结果一致。双功能 DbLcyB 和 DbLcyE 可能有助于 D. bardawil FACHB-847 中 α-胡萝卜素的高积累。有趣的是，D. bardawil FACHB-847 中叶黄素的积累对盐胁迫更为敏感，而 D. salina CCAP 19/18 中 β-胡萝卜素的积累则受到盐胁迫的诱导。简而言之，这两种杜氏藻属物种产生不同的类胡萝卜素成分可以由不同的生长条件诱导。