Pomraning Kyle R, Bredeweg Erin L, Baker Scott E
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA.
mSphere. 2017 Feb 15;2(1). doi: 10.1128/mSphere.00038-17. eCollection 2017 Jan-Feb.
Fungi accumulate lipids in a manner dependent on the quantity and quality of the nitrogen source on which they are growing. In the oleaginous yeast , growth on a complex source of nitrogen enables rapid growth and limited accumulation of neutral lipids, while growth on a simple nitrogen source promotes lipid accumulation in large lipid droplets. Here we examined the roles of nitrogen catabolite repression and its regulation by GATA zinc finger transcription factors on lipid metabolism in . Deletion of the GATA transcription factor genes and resulted in nitrogen source-specific growth defects and greater accumulation of lipids when the cells were growing on a simple nitrogen source. Deletion of , which is most similar to activators of genes repressed by nitrogen catabolite repression in filamentous ascomycetes, did not affect growth on the nitrogen sources tested. We examined gene expression of wild-type and GATA transcription factor mutants on simple and complex nitrogen sources and found that expression of enzymes involved in malate metabolism, beta-oxidation, and ammonia utilization are strongly upregulated on a simple nitrogen source. Deletion of results in overexpression of genes with GATAA sites in their promoters, suggesting that it acts as a repressor, while is required for expression of ammonia utilization genes but does not grossly affect the transcription level of genes predicted to be controlled by nitrogen catabolite repression. Both GATA transcription factor mutants exhibit decreased expression of genes controlled by carbon catabolite repression via the repressor , including genes for beta-oxidation, highlighting the complex interplay between regulation of carbon, nitrogen, and lipid metabolism. Nitrogen source is commonly used to control lipid production in industrial fungi. Here we identified regulators of nitrogen catabolite repression in the oleaginous yeast to determine how the nitrogen source regulates lipid metabolism. We show that disruption of both activators and repressors of nitrogen catabolite repression leads to increased lipid accumulation via activation of carbon catabolite repression through an as yet uncharacterized method.
真菌以一种依赖于其生长所用氮源的数量和质量的方式积累脂质。在产油酵母中，在复杂氮源上生长能实现快速生长以及中性脂质的有限积累，而在简单氮源上生长则会促进大脂滴中的脂质积累。在此，我们研究了氮分解代谢物阻遏及其由GATA锌指转录因子调控在[具体真菌名称未给出]脂质代谢中的作用。GATA转录因子基因[具体基因名称未给出]的缺失导致氮源特异性生长缺陷，并且当细胞在简单氮源上生长时脂质积累更多。与丝状子囊菌中受氮分解代谢物阻遏抑制的基因的激活因子最相似的[具体基因名称未给出]的缺失，并不影响在所测试氮源上的生长。我们检测了野生型和GATA转录因子突变体在简单和复杂氮源上的基因表达，发现参与苹果酸代谢、β-氧化和氨利用的酶的表达在简单氮源上强烈上调。[具体基因名称未给出]的缺失导致其启动子中具有GATAA位点的基因过表达，表明它作为一种阻遏物起作用，而[具体基因名称未给出]是氨利用基因表达所必需的，但并不显著影响预计受氮分解代谢物阻遏控制的基因的转录水平。两个GATA转录因子突变体都表现出受碳分解代谢物阻遏阻遏物[具体阻遏物名称未给出]调控的基因表达降低，包括β-氧化相关基因，这突出了碳、氮和脂质代谢调控之间复杂的相互作用。氮源通常用于控制工业真菌中的脂质生产。在此，我们鉴定了产油酵母中氮分解代谢物阻遏的调控因子，以确定氮源如何调控脂质代谢。我们表明，氮分解代谢物阻遏的激活因子和阻遏物的破坏通过一种尚未明确的方法激活碳分解代谢物阻遏，从而导致脂质积累增加。
