Chromochloris zofingiensis represents an industrially relevant and unique green alga, given its capability of synthesizing triacylglycerol (TAG) and astaxanthin simultaneously for storage in lipid droplets (LDs). To further decipher lipid metabolism, the nitrogen deprivation (ND)-induced LDs from C. zofingiensis were isolated, purified, and subjected to proteomic analysis. Intriguingly, many C. zofingiensis LD proteins had no orthologs present in LD proteome of the model alga Chlamydomonas reinhardtii. Seven novel LD proteins (i.e., two functionally unknown proteins, two caleosins, two lipases, and one l-gulonolactone oxidase) and the major LD protein (MLDP), which were all transcriptionally up-regulated by ND, were selected for further investigation. Heterologous expression in yeast demonstrated that all tested LD proteins were localized to LDs and all except the two functionally unknown proteins enabled yeast to produce more TAG. MLDP could restore the phenotype of mldp mutant strain and enhance TAG synthesis in wild-type strain of C. reinhardtii. Although MLDP and caleosins had a comparable abundance in LDs, they responded distinctly to ND at the transcriptional level. The two lipases, instead of functioning as TAG lipases, likely recycled polar lipids to support TAG synthesis. For the first time, we reported that l-gulonolactone oxidase was abundant in LDs and facilitated TAG accumulation. Moreover, we also proposed a novel working model for C. zofingiensis LDs. Taken together, our work unravels the unique characteristics of C. zofingiensis LDs and provides insights into algal LD biogenesis and TAG synthesis, which would facilitate genetic engineering of this alga for TAG improvement.

中文翻译：

---

卵圆藻类藻类中的脂质滴的蛋白质组学分析揭示了脂质代谢的新蛋白。

Zofingiensis绿藻代表了一种工业上相关且独特的绿藻，因为它具有合成三酰甘油（TAG）和虾青素的能力，可以同时存储在脂质滴（LDs）中。为了进一步破译脂质代谢，分离，纯化并纯化了来自Zofingiensis的氮剥夺（ND）诱导的LD，并进行了蛋白质组学分析。有趣的是，模型藻海藻Chlamydomonas reinhardtii的LD蛋白质组中没有许多直链C. zofingiensis LD蛋白。选择了全部被ND转录上调的七个新的LD蛋白（即两个功能未知的蛋白，两个caleosins，两个脂肪酶和一个l-古洛糖酸内酯氧化酶）和主要的LD蛋白（MLDP）进行进一步研究。酵母中的异源表达表明，所有测试的LD蛋白都定位于LDs，除两个功能未知的蛋白外，所有蛋白均能使酵母产生更多的TAG。MLDP可以恢复mldp突变菌株的表型并增强莱茵衣藻野生型菌株的TAG合成。尽管MLDP和caleosins在LD中具有相当的丰度，但它们在转录水平上对ND的反应明显不同。这两种脂肪酶可能​​不是作为TAG脂肪酶起作用，而是可能回收了极性脂质来支持TAG合成。第一次，我们报道了l-古洛糖酸内酯氧化酶在LD中含量丰富，并促进了TAG的积累。此外，我们还提出了一种新的工作模式，用于C. zofingiensis LD。综上所述，我们的工作揭示了C语言的独特特性。