Transcriptomic analysis reveals process of autolysis of Kluyveromyces marxianus in vacuum negative pressure and the higher temperature.

Kluyveromyces marxianus is expected to be used in the production of yeast extracts due to its good fermentation ability and nutritional properties. Yeast autolysis is a key process to produce yeast extract and vacuum negative pressure stress can be used as an effective way to assist autolysis. However, the molecular mechanism of initiating Kluyveromyces marxianus autolysis induced by vacuum negative pressure and the higher temperature is still unclear. In this study, RNA-seq technology was performed mainly to analyze autolytic processes in Kluyveromyces marxianus strains. Considerable differentially expressed genes (DEGs) of downregulation were significantly enriched in 7 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to synthesis and transport of RNA and ribosome, which indicated that abnormal protein translations had already occurred in autolytic process. Interestingly, due to obvious change of related DEGs, endoplasmic reticulum-associated degradation (ERAD) and autophagy were activated and cell wall integrity pathway was hindered. Under the continuous influence of the external stress environment, the long-term changes of the above pathways triggered a vicious circle of gradual damage to yeast cells, which is the main cause of yeast autolysis. These results may provide important clues for the in-depth interpretation of the yeast autolytic mechanism.

Transcriptomic analysis reveals MAPK signaling pathways affect the autolysis in baker's yeast.

Yeast autolysis refers to the process in which cells degrade and release intracellular contents under specific conditions by endogenous enzymes such as proteases, nucleases and lipid enzymes. Protein-rich baker's yeast is widely used to produce yeast extract in food industry, however, the molecular mechanism related to baker's yeast autolysis is still unclear. In this study, RNA-seq technology and biochemical analysis were performed to analyze the autolysis processes in baker's yeast. The differentially expressed genes (DEGs), 27 autolysis-related euKaryotic Ortholog Groups (KOG) and three types of autolysis-induced Gene Ontology (GO) were identified and analyzed in detail. A total of 143 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways under autolysis were also assigned. Interestingly, the DEGs were significantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathways and metabolic pathways, and key genes MID2, MTL1, SLT2, PTP2, HKR1 and GPD1 may play important roles in autolysis. Further quantitative PCR was performed to verify the expression pattern in baker's yeast autolysis. Together, all these results indicated that MAPK pathways might play an essential role during autolysis process through inhibiting the metabolism and disrupting cell wall in baker's yeast. This result may provide important clues for the in-depth interpretation of the yeast autolysis mechanism.