Chromochloris zofingiensis, an oleaginous microalga, is a promising feedstock for the co-production of triacylglycerol (TAG)-based biodiesel and the high-value product astaxanthin. To reveal the molecular mechanism of TAG and astaxanthin biosynthesis during transitions of sulfur nutritional status, namely sulfur-starvation (SS) and sulfur-replenishment (SR), the physiological responses and the transcriptomic dynamics of C. zofingiensis were examined. The results revealed a reversible TAG and astaxanthin accumulation under SS, which is correlated with the reduction of cell growth and protein content, indicating the reallocation of carbon. By correlating the data on the physiological and transcriptional responses to different sulfur nutritional status, a model for the underlying mechanism of TAG and astaxanthin accumulation in C. zofingiensis was postulated, which involved up-regulation of key genes including diacylglycerol acyltransferase (DGTT5) and beta-carotene ketolase (BKT1), increased energy and NADPH supply by elevating the tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate (OPP) pathway, and the increased carbon precursors (pyruvate and acetyl-CoA) through central carbon metabolism. In addition, the net enhancement of the de novo biosynthesis of fatty acids and the re-direction of the terpenoid precursors toward the branch catalyzed by lycopene beta cyclase (LCYb) and BKT1 escalated the substrate availability for the biosynthesis of TAG and astaxanthin, respectively. In this study, the time-resolved transcriptional analysis of C. zofingiensis under SS and SR conditions was reported for the first time to elucidate the regulatory roles of key enzymes, including DGTT5, BKT1 and LCYb, in the underlying mechanisms of TAG and astaxanthin accumulation.

中文翻译：

---

硫营养状态转变期间的时间分辨转录组分析提供了对绿藻 Chromochloris zofingiensis 中三酰基甘油 (TAG) 和虾青素积累的深入了解。

Chromochloris zofingiensis 是一种含油微藻，是一种很有前景的原料，可用于联产基于甘油三酯 (TAG) 的生物柴油和高价值产品虾青素。为了揭示硫营养状态转变过程中 TAG 和虾青素生物合成的分子机制，即硫饥饿 (SS) 和硫补充 (SR)，研究了 C. zofingiensis 的生理反应和转录组动力学。结果揭示了在 SS 下可逆的 TAG 和虾青素积累，这与细胞生长和蛋白质含量的减少有关，表明碳的重新分配。通过关联对不同硫营养状态的生理和转录反应的数据，建立了 TAG 和虾青素在 C. 假设 zofingiensis 涉及上调关键基因，包括二酰基甘油酰基转移酶 (DGTT5) 和 β-胡萝卜素酮酶 (BKT1)，通过提升三羧酸 (TCA) 循环和氧化戊糖磷酸 (OPP) 途径增加能量和 NADPH 供应，以及通过中心碳代谢增加的碳前体（丙酮酸和乙酰辅酶A）。此外，脂肪酸从头生物合成的净增强和萜类前体向由番茄红素 β 环化酶 (LCYb) 和 BKT1 催化的分支的重新定向分别提高了 TAG 和虾青素生物合成的底物可用性。在本研究中，时间分辨转录分析 C.