School of Food Science and Engineering, South China University of Technology, Guangzhou, China.
Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Institute of Ecological Science, School of Life Sciences, South China Normal University, Guangzhou, China.
J Cell Physiol. 2023 Jun;238(6):1324-1335. doi: 10.1002/jcp.31017. Epub 2023 Apr 23.
MADS transcription factors are involved in the regulation of fruit development and carotenoid metabolism in plants. However, whether and how carotenoid accumulation is regulated by algal MADS are largely unknown. In this study, we first used functional complementation to confirm the functional activity of phytoene synthase from the lutein-rich Dunaliella sp. FACHB-847 (DbPSY), the key rate-limiting enzyme in the carotenoid biosynthesis. Promoters of DbPSY and DbLcyB (lycopene β-cyclase) possessed multiple cis-acting elements such as light-, UV-B-, dehydration-, anaerobic-, and salt-responsive elements, W-box, and C-A-rich-G-box (MADS-box). Meanwhile, we isolated one nucleus-localized MADS transcription factor (DbMADS), belonging to type I MADS gene. Three carotenogenic genes, DbPSY, DbLcyB, and DbBCH (β-carotene hydroxylase) genes were upregulated at later stages, which was well correlated with the carotenoid accumulation. In contrast, DbMADS gene was highly expressed at lag phase with low carotenoid accumulation. Yeast one-hybrid assay and dual-luciferase reporter assay demonstrated that DbMADS could directly bind to the promoters of two carotenogenic genes, DbPSY and DbLcyB, and repress their transcriptions. This study suggested that DbMADS may act as a negative regulator of carotenoid biosynthesis by repressing DbPSY and DbLcyB at the lag phase, which provide new insights into the regulatory mechanisms of carotenoid metabolism in Dunaliella.
MADS 转录因子参与植物果实发育和类胡萝卜素代谢的调控。然而，藻类 MADS 是否以及如何调节类胡萝卜素的积累还知之甚少。在这项研究中，我们首先通过功能互补实验，证实了叶黄素丰富的杜氏盐藻（Dunaliella sp. FACHB-847）中类胡萝卜素生物合成的关键限速酶——八氢番茄红素合酶（phytoene synthase，DbPSY）的功能活性。DbPSY 和 DbLcyB（番茄红素β-环化酶）的启动子具有多个顺式作用元件，如光、UV-B、脱水、厌氧和盐响应元件、W 盒和富含 C-A-G 盒（MADS 盒）。同时，我们分离到一个定位于细胞核内的 MADS 转录因子（DbMADS），属于 I 型 MADS 基因。三个类胡萝卜素生物合成基因，DbPSY、DbLcyB 和 DbBCH（β-胡萝卜素羟化酶）在后期表达上调，这与类胡萝卜素的积累密切相关。相比之下，DbMADS 基因在低类胡萝卜素积累的迟滞期高表达。酵母单杂交实验和双荧光素酶报告基因实验表明，DbMADS 可以直接结合到两个类胡萝卜素生物合成基因 DbPSY 和 DbLcyB 的启动子上，并抑制它们的转录。这项研究表明，DbMADS 可能通过在迟滞期抑制 DbPSY 和 DbLcyB 的表达，作为类胡萝卜素生物合成的负调控因子，为杜氏盐藻中类胡萝卜素代谢的调控机制提供了新的见解。
