MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker's yeast in lean dough.
MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker's yeast in lean dough.
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MAL62 过表达可增强尿苷二磷酸葡萄糖依赖性海藻糖合成和甘油代谢，从而对瘦面团中的面包酵母进行冷冻保护。
DOI：
10.1186/s12934-020-01454-6
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发表时间：
2020-10-19
影响因子：
6.4
通讯作者：
Zhu WB
中科院分区：
文献类型：
--
作者：
Sun X;Zhang J;Fan ZH;Xiao P;Li F;Liu HQ;Zhu WB
在酿酒酵母中，α -葡萄糖苷酶（麦芽糖酶）是麦芽糖代谢的关键酶。此外，α -葡萄糖苷酶编码基因MAL62的过表达已被证明可以提高酵母在瘦肉面团中的抗冻能力。但其低温保护机制尚不清楚。RNA测序（RNA-seq）显示MAL62过表达增加了尿苷二磷酸葡萄糖（UDPG）依赖性海藻糖的合成。转录物丰度的变化由定量逆转录聚合酶链反应（qRT-PCR）和酶活性测定证实。当udpg依赖性海藻糖合成酶活性被消除时，MAL62过表达不能促进细胞内海藻糖的合成。此外，在缺乏海藻糖合成的菌株中，MAL62过表达的菌株在优先冻结后期的细胞活力略有降低，这可能与细胞内甘油浓度的增加有关。这一结果与甘油合成途径成员的转录升高一致。MAL62过表达增加抗冻性主要是通过udpg依赖途径增加海藻糖含量来实现的，甘油也起着重要作用。这些发现揭示了酵母对瘦面包面团冷冻反应的机制，并有助于改善工业酵母菌株。
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. 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. 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.
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