Ran Yulu, Xu Hui, Yang Qingzhuoma, Xu Yi, Yang Huahao, Qiao Dairong, Cao Yi
Microbiology and Metabolic Engineering key laboratory of Sichuan Province, College of Life Science, Sichuan University, Chengdu, Sichuan 610065 People's Republic of China.
Biotechnol Biofuels Bioprod. 2022 Oct 8;15(1):103. doi: 10.1186/s13068-022-02177-z.
In oleaginous yeast, nitrogen limitation is a critical parameter for lipid synthesis. GATA-family transcriptional factor GAT1, a member of the target of rapamycin (TOR) pathway and nitrogen catabolite repression (NCR), regulates nitrogen uptake and utilization. Therefore, it is significant to study the SpGAT1 regulatory mechanism of lipid metabolism for conversion of biomass to microbial oil in zwy-2-3.
Compared with WT, , and OE::1 , the lipid yield of OE::1 increased markedly in the low carbon and nitrogen ratio (C/N ratio) mediums, while the lipid yield and residual sugar of decreased in the high C/N ratio medium. According to yeast two-hybrid assays, SpGAT1 interacted with SpMIG1, and its deletion drastically lowered SpMIG1 expression on the high C/N ratio medium. MIG1 deletion has been found in earlier research to affect glucose metabolic capacity, resulting in a prolonged lag period. Therefore, we speculated that SpGAT1 influenced glucose consumption rate across SpMIG1. Based on yeast one-hybrid assays and qRT-PCR analyses, SpGAT1 regulated the glyoxylate cycle genes ICL1, ICL2, and pyruvate bypass pathway gene ACS, irrespective of the C/N ratio. SpGAT1 also could bind to the ACAT2 promoter in the low C/N medium and induce sterol ester (SE) accumulation.
Our findings indicated that SpGAT1 positively regulated lipid metabolism in zwy-2-3, but that its regulatory patterns varied depending on the C/N ratio. When the C/N ratio was high, SpGAT1 interacted with SpMIG1 to affect carbon absorption and utilization. SpGAT1 also stimulated lipid accumulation by regulating essential lipid anabolism genes. Our insights might spur more research into how nitrogen and carbon metabolism interact to regulate lipid metabolism.
在产油酵母中，氮限制是脂质合成的关键参数。GATA家族转录因子GAT1是雷帕霉素靶蛋白（TOR）途径和氮分解代谢物阻遏（NCR）的成员之一，可调节氮的吸收和利用。因此，研究zwy-2-3中SpGAT1对脂质代谢的调控机制对于将生物质转化为微生物油脂具有重要意义。
与野生型、[缺失突变体]和OE::1相比，OE::1在低碳氮比（C/N比）培养基中的脂质产量显著增加，而在高C/N比培养基中，[缺失突变体]的脂质产量和残余糖含量降低。根据酵母双杂交试验，SpGAT1与SpMIG1相互作用，其缺失显著降低了高C/N比培养基上SpMIG1的表达。早期研究发现MIG1缺失会影响葡萄糖代谢能力，导致延滞期延长。因此，我们推测SpGAT1通过SpMIG1影响葡萄糖消耗速率。基于酵母单杂交试验和qRT-PCR分析，无论C/N比如何，SpGAT1都能调节乙醛酸循环基因ICL1、ICL2和丙酮酸旁路途径基因ACS。SpGAT1还可以在低C/N培养基中与ACAT2启动子结合并诱导甾醇酯（SE）积累。
我们的研究结果表明，SpGAT1对zwy-2-3中的脂质代谢具有正向调控作用，但其调控模式因C/N比而异。当C/N比高时，SpGAT1与SpMIG1相互作用以影响碳的吸收和利用。SpGAT1还通过调节关键的脂质合成代谢基因来刺激脂质积累。我们的见解可能会促使更多关于氮和碳代谢如何相互作用以调节脂质代谢的研究。
