The expression pattern of β-carotene ketolase gene restricts the accumulation of astaxanthin in Dunaliella under salt stress
The expression pattern of β-carotene ketolase gene restricts the accumulation of astaxanthin in Dunaliella under salt stress
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盐胁迫下β-胡萝卜素酮酶基因的表达模式限制杜氏藻虾青素的积累
DOI：
10.1002/jcp.30647
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发表时间：
2021-11-23
影响因子：
5.6
通讯作者：
Jiang, Jian-Guo
中科院分区：
文献类型：
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作者：
Chen, Hao-Hong;He, Yu-Jing;Jiang, Jian-Guo
杜氏盐藻能够积累大量的β-胡萝卜素，β-胡萝卜素通常被认为是其类胡萝卜素代谢的终末产物。本研究证明了D.桑拿具有催化合成β-胡萝卜素下游产物虾青素的酮醇酶（DsBKT）。因此，D.盐藻不合成虾青素是本研究的目的。在大肠杆菌中进行功能互补试验，结果表明DsBKT具有高效的酮醇酶活性，可降解β-胡萝卜素和玉米黄质，并能产生虾青素，表明杜氏藻中存在完整的虾青素产生基因。与盐胁迫诱导番茄红素环化酶（催化β-胡萝卜素合成）的表达不同，DsBKT在正常和胁迫条件下的表达量都很低，这可能是D.盐藻不能积累虾青素。相反，以富含虾青素的雨生红球藻为对照，其BKT基因在盐胁迫下显著上调。进一步研究表明，DsBKT启动子具有较强的启动能力，能够稳定驱动ble-egfp在D. salina。显然，DsBKT启动子不是DsBKT不表达的原因，可能是非编码RNA引起的。
Dunaliella salina can accumulate a large amount of beta-carotene which is generally considered to be its terminal product of carotenoid metabolism. In this study, it was proved that D. sauna has the ketolase (DsBKT) of catalyzing the synthesis of astaxanthin, the downstream products of beta-carotene. Therefore, the reason why D. salina does not synthesize astaxanthin is the purpose of this study. The enzymatic activity of DsBKT was detected by functional complementation assays in Escherichia coli, results showed that DsBKT had efficient ketolase activity toward beta-carotene and zeaxanthin to produce astaxanthin, indicating that there were complete astaxanthin-producing genes in Dunaliella. Unlike the induced expression of Lycopene cyclase (catalyzing beta-carotene synthesis) under salt stress, the expression of DsBKT was very low under both normal and stress conditions, which may be the main reason why D. salina cannot accumulate astaxanthin. On the contrary, with the astaxanthin-rich Haematococcus pluvialis as a control, its BKT gene was significantly upregulated under salt stress. Further study showed that DsBKT promoter had strong promoter ability and could stably drive the expression of ble-egfp in D. salina. Obviously, DsBKT promoter is not the reason of DsBKT not being expressed which may be caused by Noncoding RNA.