敲除MIG1和SNF1基因对酿酒酵母共利用葡萄糖和木糖的影响

Effect of MIG1 and SNF1 deletion on simultaneous utilization of glucose and xylose by Saccharomyces cerevisiae

摘要:

Mig1和Snf1是酿酒酵母葡萄糖阻遏效应的两个关键调控因子。为了提高酿酒酵母工程菌同时利用葡萄糖和木糖的能力，分别对MIG1和SNF1基因进行了单敲除和双敲除，并通过摇瓶发酵实验和RNA-Seq转录组分析，初步揭示了Mig1和Snf1可能影响葡萄糖和木糖共利用表达差异基因的层级调控机制。研究结果表明，MIG1单敲除对混合糖的共利用影响不大；SNF1单敲除会加快混合糖中木糖的利用而且葡萄糖和木糖可以被同时利用，这可能归因于SNF1单敲除会解除对一些氮分解代谢阻遏基因表达的抑制，从而促进了细胞对氮源营养的利用；进一步敲除MIG1，会解除更多氮分解代谢阻遏基因表达的抑制，以及一些碳中心代谢途径基因表达上调。虽然MIG1和SNF1双敲除菌株利用葡萄糖加快而利用木糖变慢，但是葡萄糖和木糖可以被同时利用，进而加快乙醇的积累。综上所述，MIG1和SNF1的敲除导致氮分解阻遏基因表达上调，有助于促进葡萄糖和木糖的共利用；解析Mig1和Snf1对氮分解阻遏基因的层级调控作用，为进一步提高葡萄糖和木糖的共利用提供新的靶点。

Abstract:

Mig1 and Snf1 are two key regulatory factors involved in glucose repression of Saccharomyces cerevisiae. To enhance simultaneous utilization of glucose and xylose by engineered S. cerevisiae, single and double deletion strains of MIG1 and SNF1 were constructed. Combining shake flask fermentations and transcriptome analysis by RNA-Seq, the mechanism of Mig1 and Snf1 hierarchically regulating differentially expressed genes that might affect simultaneous utilization of glucose and xylose were elucidated. MIG1 deletion did not show any significant effect on co-utilization of mixed sugars. SNF1 deletion facilitated xylose consumption in mixed sugars as well as co-utilization of glucose and xylose, which might be due to that the SNF1 deletion resulted in the de-repression of some genes under nitrogen catabolite repression, thereby favorable to the utilization of nitrogen nutrient. Further deletion of MIG1 gene in the SNF1 deletion strain resulted in the de-repression of more genes under nitrogen catabolite repression and up-regulation of genes involved in carbon central metabolism. Compared with wild type strain, the MIG1 and SNF1 double deletion strain could co-utilize glucose and xylose, and accelerate ethanol accumulation, although this strain consumed glucose faster and xylose slower. Taken together, the MIG1 and SNF1 deletions resulted in up-regulation of genes under nitrogen catabolite repression, which could be beneficial to simultaneous utilization of glucose and xylose. Mig1 and Snf1 might be involved in the hierarchical regulatory network of genes under nitrogen catabolite repression. Dissection of this regulatory network could provide further insights to new targets for improving co-utilization of glucose and xylose.