Presentation Information
[4Ferm-04]Role of the complex sphingolipid MIPC in ethanol tolerance and fermentation capacity in budding yeast
○Saki Sugihara1, Reo Susami1, Shion Ito1, Yohei Ishibashi3, Ayano Koga3, Masaya Shimada1, Taisei Yuyama2, Daisuke Watanabe2, Tomoyuki Nakagawa1, Motohiro Tani1,3 (1. Gifu Univ. (Japan), 2. NAIST (Japan), 3. Kyushu Univ. (Japan))
Keywords:
Saccharomyces cerevisiae,Alcohol fermentaiton,sphingolipid,sterol
The budding yeast Saccharomyces cerevisiae produces ethanol during fermentation and therefore possesses a high level of ethanol tolerance to sustain growth under fermentative conditions. However, the molecular basis underlying this tolerance remains incompletely understood. We have previously demonstrated that the structural diversity of complex sphingolipids, major components of biological membranes, is required for adaptation to various environmental stresses (MBoC 33, ar105, 2022). In this study, we show that the biosynthesis of mannosylinositol phosphorylceramide (MIPC), a class of complex sphingolipids, plays a crucial role in maintaining ethanol tolerance and fermentation capacity in yeast.
Cells lacking MIPC synthases (csg1Δ csh1Δ, hereafter referred to as ccΔ) exhibited marked hypersensitivity to ethanol. In ccΔ cells, defects in cell wall remodeling were observed under ethanol stress conditions. Furthermore, ethanol stress induced Rim101-dependent reorganization of plasma membrane microdomains (eisosomes) in ccΔ cells, and deletion of RIM101 and/or PIL1 in ccΔ cells further reduced cell viability and exacerbated abnormalities in plasma membrane lipid order in the presence of ethanol. These results suggest that MIPC biosynthesis contributes to ethanol tolerance by regulating both cell wall integrity and plasma membrane organization. Under simulated brewing conditions that generate high levels of ethanol, ccΔ cells exhibited delayed growth, increased cell death, and reduced CO2 production, indicating hypersensitivity even to endogenously produced ethanol. The phenotypic defects of ccΔ cells were further exacerbated by additional deletions of genes involved in ergosterol biosynthesis (ERG2, ERG3, ERG4, and ERG5). In contrast, deletion of genes involved in retrograde transport of ergosterol from the plasma membrane to the endoplasmic reticulum (LAM1, SIP3, and YSP2) partially suppressed ethanol hypersensitivity caused by the loss of MIPC biosynthesis. These findings indicate that MIPC and ergosterol biosynthesis coordinately contribute to ethanol tolerance and fermentation performance in yeast.
Analysis of complex sphingolipid composition in various industrial yeast strains used for sake and wine fermentation revealed that many strains accumulate high levels of MIPC. Notably, all strains of the sake yeast Kyokai no. 7 lineage, which carry a frameshift mutation in RIM15, exhibited elevated MIPC levels. Loss of RIM15 function is known to enhance fermentation capacity while reducing stress tolerance (AEM 78, 4008, 2012). We further found that combined deletion of CSG1, CSH1, and RIM15 led to a more severe reduction in ethanol tolerance than each single deletion. These results suggest that Kyokai no. 7-derived strains may optimize the balance between fermentation performance and stress resistance through increased MIPC accumulation.
Cells lacking MIPC synthases (csg1Δ csh1Δ, hereafter referred to as ccΔ) exhibited marked hypersensitivity to ethanol. In ccΔ cells, defects in cell wall remodeling were observed under ethanol stress conditions. Furthermore, ethanol stress induced Rim101-dependent reorganization of plasma membrane microdomains (eisosomes) in ccΔ cells, and deletion of RIM101 and/or PIL1 in ccΔ cells further reduced cell viability and exacerbated abnormalities in plasma membrane lipid order in the presence of ethanol. These results suggest that MIPC biosynthesis contributes to ethanol tolerance by regulating both cell wall integrity and plasma membrane organization. Under simulated brewing conditions that generate high levels of ethanol, ccΔ cells exhibited delayed growth, increased cell death, and reduced CO2 production, indicating hypersensitivity even to endogenously produced ethanol. The phenotypic defects of ccΔ cells were further exacerbated by additional deletions of genes involved in ergosterol biosynthesis (ERG2, ERG3, ERG4, and ERG5). In contrast, deletion of genes involved in retrograde transport of ergosterol from the plasma membrane to the endoplasmic reticulum (LAM1, SIP3, and YSP2) partially suppressed ethanol hypersensitivity caused by the loss of MIPC biosynthesis. These findings indicate that MIPC and ergosterol biosynthesis coordinately contribute to ethanol tolerance and fermentation performance in yeast.
Analysis of complex sphingolipid composition in various industrial yeast strains used for sake and wine fermentation revealed that many strains accumulate high levels of MIPC. Notably, all strains of the sake yeast Kyokai no. 7 lineage, which carry a frameshift mutation in RIM15, exhibited elevated MIPC levels. Loss of RIM15 function is known to enhance fermentation capacity while reducing stress tolerance (AEM 78, 4008, 2012). We further found that combined deletion of CSG1, CSH1, and RIM15 led to a more severe reduction in ethanol tolerance than each single deletion. These results suggest that Kyokai no. 7-derived strains may optimize the balance between fermentation performance and stress resistance through increased MIPC accumulation.
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