Effect of overexpression of SNF1 on the transcriptional and metabolic landscape of baker's yeast under freezing stress

Freezing stress is the key factor that affecting the cell activity and fermentation performance of baker's yeast in frozen dough production. Generally, cells protect themselves from injury and maintain metabolism by regulating gene expression and modulating metabolic patterns in stresses. The Snf1 protein kinase is an important regulator of yeast in response to stresses. In this study, we aim to study the role of the catalytic subunit of Snf1 protein kinase in the cell tolerance and dough leavening ability of baker's yeast during freezing. Furthermore, the effects of SNF1 overexpression on the global gene expression and metabolite profile of baker's yeast before and after freezing were analysed using RNA-sequencing and untargeted UPLC - QTOF-MS/MS, respectively. The results suggest that overexpression of SNF1 was effective in enhancing the cell tolerance and fermentation capacity of baker's yeast in freezing, which may be related to the upregulated proteasome, altered metabolism of carbon sources and protectant molecules, and changed cell membrane components. SNF1 overexpression altered the level of leucin, proline, serine, isoleucine, arginine, homocitrulline, glycerol, palmitic acid, lysophosphatidylcholine (LysoPC), and lysophosphatidylethanolamine (LysoPE) before freezing, conferring cells resistance in freezing. After freezing, relative high level of proline, lysine, and glycerol maintained by SNF1 overexpression with increased content of LysoPC and LysoPE. This study will increase the knowledge of the cellular response of baker's yeast cells to freezing and provide new opportunities for the breeding of low-temperature resistant strains.