Polyploid engineering by increasing mutant gene dosage in yeasts

Abstract

The yeast Saccharomyces cerevisiae, widely used for ethanol production, is one of the best-understood biological systems. Diploid strains of S. cerevisiae are preferred for industrial use due to the better fermentation efficiency, in terms of vitality and endurance as compared to those of haploid strains. Whole-genome duplications is known to promote adaptive mutations in microorganisms, and allelic variations considerably contribute to the product composition in ethanol fermentation. Although fermentation can be regulated using various strains of yeast, it is quite difficult to make fine adjustment of each component in final products. In this study, we demonstrate the use of polyploids with varying gene dosage (the number of copies of a particular gene present in a genome) in the regulation of ethanol fermentation. Ethyl caproate is one of the major flavouring agents in a Japanese alcoholic beverage called sake. A point mutation in FAS2 encoding the a subunit of fatty acid synthetase induces an increase in the amount of caproic acid, a precursor of ethyl caproate. Using the FAS2 as a model, we generated and evaluated yeast strains with varying mutant gene dosage. We demonstrated the possibility to increase mutant gene dosage via loss of heterozygosity in diploid and tetraploid strains. Productivity of ethyl caproate gradually increased with mutant gene dosage among tetraploid strains. This approach can potentially be applied to a variety of yeast strain development via growth-based screening.

Complete dominant inheritance of intracellular leucine accumulation traits in polyploid yeasts

“…In the previous report (Fukuda et al, 2021), we indicated that the phenotypic change induced by 1 copy of the partial dominant mutation in the FAS2 gene obviously declined as yeast ploidy increased. For quantitative evaluation of the genetic dominance of the LEU4 G516S mutation, in the current study, dose-response curves for TFL were compared among strains with a hetero allelic mutation LEU4 G516S .…”

Induction of Chromosomal Aneuploids from Brewery Shochu Yeast with Novel Brewery Characteristics

“…Karyotyping: The extraction of genomic DNA and karyotyping was performed according to the previous study [8,9]. DNA was extracted using the alkali extraction method.…”

“…However, some brewery Fermentation 2022, 8, 62 2 of 12 yeasts have three chromosomes and are called aneuploids [5,6]. Aneuploidy yeast cells have physiologies that are different from euploidy yeast cells [7,8]. Recently, we first showed that the chromosomal aneuploidy of brewery yeasts alters brewery profiles [9].…”

Practical Approaches for the Yeast Saccharomyces cerevisiae Genome Modification

“…It is especially common in industrial strains where it is thought to be a result of adaptation to industrial conditions, fermentation target products or by-products [200]. Aneuploidy can be a result of a strain's adaptation to different drugs and confer drug resistance that has perspectives in biotechnological engineering [202,203]. At the same time aneuploidy may lead to a decrease in viability, apparently due to the imbalance of multiple proteins and the increased burden on protein quality control systems [204][205][206].…”