<i>MAL62</i> Overexpression Enhances Freezing Tolerance of Baker’s Yeast in Lean Dough by Enhancing Tps1 Activity and Maltose Metabolism

Fan

et al. 2020

Preprint

Self Cite

Background: In Saccharomyces cerevisiae, the alpha-glucosidase (maltase) is a key enzyme in maltose metabolism. Overexpression of the alpha-glucosidase-encoding gene MAL62 has been shown to increase the freezing tolerance of yeast in lean dough. However, its cryoprotection mechanism is still not clear.Results: RNA sequencing (RNA-seq) revealed that MAL62 overexpression increased transcription of uridine diphosphoglucose (UDPG)-dependent trehalose synthesis. The changes in transcript abundance were confirmed by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and enzyme activity assays. When the UDPG-dependent trehalose synthase activity was abolished, MAL62 overexpression failed to promote the synthesis of intracellular trehalose. Moreover, in strains lacking trehalose synthesis, cell viability in the late phase of prefermentation freezing coupled with MAL62 overexpression was slightly reduced, which can be explained by the increase in intracellular glycerol concentration which was consistent with the elevated transcription of glycerol synthesis pathways. Conclusions: The increased freezing tolerance by MAL62 overexpression is mainly achieved by the increased trehalose content via the UDPG-dependent pathway, and glycerol plays a secondary role. These findings shed new light to the mechanism of yeast response to freezing in lean bread dough and can help the improvement of industrial yeast strains.

Section: Discussionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker’s yeast in lean dough

Fan

et al. 2020

Preprint

Self Cite

“…Using mutants of S. cerevisiae deficient in trehalose synthesis, degradation, or transport, studies have shown that trehalose can protect cells exposed to freezing and dehydration [ 40 – 42 ]. We have previously reported that the enhanced freezing tolerance by MAL62 overexpression is related to the increased activity of Tps1 [ 16 ]. Our current study provides further evidence that genes involved in starch and sucrose metabolism, including GLK1 , EMI2 , HXK1 , HXK2 , PGM2 , PRM15 , and UGP1 , had a higher expression level in the B + MAL62 strain (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Each gene complex encodes a maltose permease, an alpha-glucosidase, and a transacting MAL-activator [ 14 ]. We have shown previously that overexpression of MAL62 enhances the cryotolerance of baker’s yeast [ 15 ] and speculated that multiple pathways may be involved in this phenomenon [ 16 ]. However, the mechanism for the enhanced freezing tolerance is still unknown.…”

Section: Introductionmentioning

confidence: 99%

MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker’s yeast in lean dough

et al. 2020

Microb Cell Fact

Self Cite

Background In Saccharomyces cerevisiae, alpha-glucosidase (maltase) is a key enzyme in maltose metabolism. In addition, the overexpression of the alpha-glucosidase-encoding gene MAL62 has been shown to increase the freezing tolerance of yeast in lean dough. However, its cryoprotection mechanism is still not clear. Results RNA sequencing (RNA-seq) revealed that MAL62 overexpression increased uridine diphosphoglucose (UDPG)-dependent trehalose synthesis. The changes in transcript abundance were confirmed by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and enzyme activity assays. When the UDPG-dependent trehalose synthase activity was abolished, MAL62 overexpression failed to promote the synthesis of intracellular trehalose. Moreover, in strains lacking trehalose synthesis, the cell viability in the late phase of prefermentation freezing coupled with MAL62 overexpression was slightly reduced, which can be explained by the increase in the intracellular glycerol concentration. This result was consistent with the elevated transcription of glycerol synthesis pathway members. Conclusions The increased freezing tolerance by MAL62 overexpression is mainly achieved by the increased trehalose content via the UDPG-dependent pathway, and glycerol also plays an important role. These findings shed new light on the mechanism of yeast response to freezing in lean bread dough and can help to improve industrial yeast strains.

“…Using mutants of S. cerevisiae de cient in trehalose synthesis, degradation, or transport, studies have shown that trehalose can protect cells exposed to freezing and dehydration [40][41][42]. We have previously reported that the enhanced freezing tolerance by MAL62 overexpression is related to the increased activity of Tps1 [16]. Our current study provides further evidence that genes involved in starch and sucrose metabolism, including GLK1, EMI2, HXK1, HXK2, PGM2, PRM15, and UGP1, had a higher expression level in the B+MAL62 strain (Fig.…”

Section: Discussionmentioning

confidence: 99%

MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker’s yeast in lean dough

Fan

et al. 2020

Preprint

Self Cite

Background: In Saccharomyces cerevisiae, alpha-glucosidase (maltase) is a key enzyme in maltose metabolism. In addition, the overexpression of the alpha-glucosidase-encoding gene MAL62 has been shown to increase the freezing tolerance of yeast in lean dough. However, its cryoprotection mechanism is still not clear.Results: RNA sequencing (RNA-seq) revealed that MAL62 overexpression increased uridine diphosphoglucose (UDPG)-dependent trehalose synthesis. The changes in transcript abundance were confirmed by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and enzyme activity assays. When the UDPG-dependent trehalose synthase activity was abolished, MAL62 overexpression failed to promote the synthesis of intracellular trehalose.Moreover, in strains lacking trehalose synthesis, the cell viability in the late phase of prefermentation freezing coupled with MAL62 overexpression was slightly reduced, which can be explained by the increase in the intracellular glycerol concentration. This result was consistent with the elevated transcription of glycerol synthesis pathway members.Conclusions: The increased freezing tolerance by MAL62 overexpression is mainly achieved by the increased trehalose content via the UDPG-dependent pathway, and glycerol also plays an important role. These findings shed new light on the mechanism of yeast response to freezing in lean bread dough and can help to improve industrial yeast strains.