Abstract
BackgroundIn the yeast Saccharomyces cerevisiae, genes containing UASINO sequences are regulated by the Ino2/Ino4 and Opi1 transcription factors, and this regulation controls lipid biosynthesis. The expression level of INO2 and INO4 genes (INO-level) at different nutrient limited conditions might lead to various responses in yeast lipid metabolism.MethodsIn this study, we undertook a global study on how INO-levels (transcription level of INO2 and INO4) affect lipid metabolism in yeast and we also studied the effects of single and double deletions of the two INO-genes (deficient effect). Using 2 types of nutrient limitations (carbon and nitrogen) in chemostat cultures operated at a fixed specific growth rate of 0.1 h-1 and strains having different INO-level, we were able to see the effect on expression level of the genes involved in lipid biosynthesis and the fluxes towards the different lipid components. Through combined measurements of the transcriptome, metabolome, and lipidome it was possible to obtain a large dataset that could be used to identify how the INO-level controls lipid metabolism and also establish correlations between the different components.ResultsIn this study, we undertook a global study on how INO-levels (transcription level of INO2 and INO4) affect lipid metabolism in yeast and we also studied the effects of single and double deletions of the two INO-genes (deficient effect). Using 2 types of nutrient limitations (carbon and nitrogen) in chemostat cultures operated at a fixed specific growth rate of 0.1 h-1 and strains having different INO-level, we were able to see the effect on expression level of the genes involved in lipid biosynthesis and the fluxes towards the different lipid components. Through combined measurements of the transcriptome, metabolome, and lipidome it was possible to obtain a large dataset that could be used to identify how the INO-level controls lipid metabolism and also establish correlations between the different components.ConclusionsOur analysis showed the strength of using a combination of transcriptome and lipidome analysis to illustrate the effect of INO-levels on phospholipid metabolism and based on our analysis we established a global regulatory map.
Highlights
In the yeast Saccharomyces cerevisiae, genes containing UASINO sequences are regulated by the Ino2/ Ino4 and Opi1 transcription factors, and this regulation controls lipid biosynthesis
Since the Ino2-Ino4 heterodimer regulates positively the expression of INO1 and other phospholipid genes containing UASINO element [31,50], deletion of INO2 and INO4 results in a requirement for supplementation of myoinositol
The spot test showed that opi1Δ as well as reference strain are prototroph for inositol but at least 75 μM of inositol is sufficient for low INO-level strains to grow
Summary
In the yeast Saccharomyces cerevisiae, genes containing UASINO sequences are regulated by the Ino2/ Ino and Opi transcription factors, and this regulation controls lipid biosynthesis. Opi is necessary for repression of ICRE-dependent transcription when inositol-choline is present in excess [8,11]. Under this condition, Opi is localized in the nucleus [12] and prevents Ino from activation of target genes by recruiting the pleiotropic co-repressors such as the Cyc8/Tup complex [13,14] or Sin3p [15,16,17,18,19]. A genome wide transcription analysis of the effect of varying INO-levels that effect lipid metabolism has never been studied before
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