Targeted transcriptomic study of the implication of central metabolic pathways in mannosylerythritol lipids biosynthesis in <i>Pseudozyma antarctica</i> T-34

Pseudozyma antarctica is a nonpathogenic phyllosphere yeast known as an excellent producer of industrial lipases and mannosylerythritol lipids (MELs), which are multi-functional glycolipids. The fungus produces a much higher amount of MELs from vegetable oil than from glucose, whereas its close relative, Ustilago maydis UM521, produces a lower amount of MELs from vegetable oil. In the present study, we used previous gene expression profiles measured by DNA microarray analyses after culturing on two carbon sources, glucose and soybean oil, to further characterize MEL biosynthesis in P. antarctica T-34. A total of 264 genes were found with induction ratios and expression intensities under oily conditions with similar tendencies to those of MEL cluster genes. Of these, 93 were categorized as metabolic genes using the Eukaryotic Orthologous Groups classification. Within this metabolic category, amino acids, carbohydrates, inorganic ions, and secondary metabolite metabolism, as well as energy production and conversion, but not lipid metabolism, were enriched. Furthermore, genes involved in central metabolic pathways, such as glycolysis and the tricarboxylic acid cycle, were highly induced in P. antarctica T-34 under oily conditions, whereas they were suppressed in U. maydis UM521. These results suggest that the central metabolism of P. antarctica T-34 under oily conditions contributes to its excellent oil utilization and extracellular glycolipid production.南极假丝酵母（Pseudozyma antarctica）是一种非致病性叶际酵母，作为工业脂肪酶与甘露糖赤藓糖醇脂（mannosylerythritol lipids，MELs）的高效生产菌株而广受认可，该类物质属于多功能糖脂化合物。该真菌以植物油为碳源时合成的MELs产量远高于葡萄糖；而其近缘物种玉米黑粉菌（Ustilago maydis）UM521以植物油为碳源时的MELs产量则较低。本研究借助此前在葡萄糖与大豆油两种碳源下培养后，通过DNA微阵列（DNA microarray）分析获得的基因表达谱，进一步解析南极假丝酵母T-34的MEL生物合成特征。最终筛选得到264个基因，其在油质培养条件下的诱导倍数与表达强度变化趋势与MEL基因簇基因高度相似。其中93个基因通过真核直系同源基团（Eukaryotic Orthologous Groups）分类系统被归类为代谢基因。在该代谢类别中，氨基酸代谢、碳水化合物代谢、无机离子代谢、次生代谢物代谢，以及能量产生与转换通路均存在富集，但脂类代谢通路未出现富集。此外，在油质培养条件下，南极假丝酵母T-34中糖酵解（glycolysis）、三羧酸循环（tricarboxylic acid cycle）等中心代谢通路相关基因被显著诱导上调，而玉米黑粉菌UM521中的此类基因则被抑制。上述结果表明，油质培养环境下南极假丝酵母T-34的中心代谢过程，助力其实现高效的植物油利用与胞外糖脂生产。