Acetyl-CoA synthetase is activated as part of the PDH-bypass in the oleaginous green alga Chlorella desiccata.
Acetyl-CoA synthetase is activated as part of the PDH-bypass in the oleaginous green alga Chlorella desiccata.
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DOI：
10.1093/jxb/erv424
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发表时间：
2015-12
影响因子：
6.9
通讯作者：
Pick U
中科院分区：
文献类型：
--
作者：
Avidan O;Pick U
质体乙酰辅酶A合酶（ptACS-2）和ATP柠檬酸裂解酶的上调产油小球藻干燥在氮剥夺。ptACS-2是支持三酰甘油积累的丙酮酸脱氢酶旁路的一部分。在最近的研究中，已经表明，在产油绿色小球藻干燥小球藻中三酰甘油（TAG）的生物合成之前，乙酰辅酶A（Ac-CoA）水平的大幅增加和质体丙酮酸脱氢酶（ptPDH）的上调。有人提出，积累高TAG的能力关键取决于Ac-CoA产量的提高。在这项研究中，两个替代的Ac-CoA生产商-质体Ac-CoA合成酶（ptACS）和ATP柠檬酸裂解酶（ACL）-被证明是上调之前，TAG积累下的氮剥夺下的含油物种C。而对中度TAG的杜氏盐藻和莱茵衣藻则无明显的抑制作用。内源性乙酸盐的产生和放射性标记的乙酸盐掺入脂质的测量与ptACS的上调一致，但表明其对整体TAG生物合成的贡献可以忽略不计。ACS的诱导和内源性乙酸的产生与乙醇脱氢酶的激活相关，表明ptACS的上调与C.干的因此，我们认为C.需要干燥剂以通过控制丙酮酸水平达到ptPHD和/或mtPDH而在氮剥夺下实现高速率的脂质生物合成。这可能是微藻中大量TAG积累的重要参数。
Plastidic acetyl-CoA synthase (ptACS-2) and ATP citrate lyase are upregulated in the oleaginous alga Chlorella desiccata during nitrogen deprivation. ptACS-2 is part of the pyruvate dehydrogenase bypass which supports triacylglycerol accumulation. In a recent study, it has been shown that biosynthesis of triacylglycerol (TAG) in the oleaginous green alga Chlorella desiccata is preceded by a large increase in acetyl-coenzyme A (Ac-CoA) levels and by upregulation of plastidic pyruvate dehydrogenase (ptPDH). It was proposed that the capacity to accumulate high TAG critically depends on enhanced production of Ac-CoA. In this study, two alternative Ac-CoA producers—plastidic Ac-CoA synthase (ptACS) and ATP citrate lyase (ACL)—are shown to be upregulated prior to TAG accumulation under nitrogen deprivation in the oleaginous species C. desiccata, but not in the moderate TAG accumulators Dunaliella tertiolecta and Chlamydomonas reinhardtii. Measurements of endogenous acetate production and of radiolabelled acetate incorporation into lipids are consistent with the upregulation of ptACS, but suggest that its contribution to the overall TAG biosynthesis is negligible. Induction of ACS and production of endogenous acetate are correlated with activation of alcohol dehydrogenase, suggesting that the upregulation of ptACS is associated with activation of PDH-bypass in C. desiccata. It is proposed that activation of the PDH-bypass in C. desiccata is needed to enable a high rate of lipid biosynthesis under nitrogen deprivation by controlling the level of pyruvate reaching ptPHD and/or mtPDH. This may be an important parameter for massive TAG accumulation in microalgae.