Genomic saturation mutagenesis and polygenic analysis identify novel yeast genes affecting ethyl acetate production, a non-selectable polygenic trait
Authors:Tom Den Abt1,2, Ben Souffriau1,2, Maria R. Foulquié-Moreno1,2, Jorge Duitama3, and Johan M. Thevelein1,2
1 Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven.
2 Department of Molecular Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium.
3 Agrobiodiversity Research Area, International Center for Tropical Agriculture (CIAT), Cali, Colombia.
Keywords:
mutant screen, genomic mutagenesis, non-selectable trait, polygenic trait, QTL mapping, genetic basis, flavor production, ethyl acetate production.
Related Article(s)?
Chris Curtin and Toni Cordente (2016). What’s old is new again: yeast mutant screens in the era of pooled segregant analysis by genome sequencing. Microbial Cell 3(4): 132-134., 10.15698/mic2016.04.488
Corresponding Author(s):
Conflict of interest statement:
The authors declare no conflict of interest.
Please cite this article as:
Tom Den Abt, Ben Souffriau, Maria R. Foulquié-Moreno, Jorge Duitama, and Johan M. Thevelein (2016). Genomic saturation mutagenesis and polygenic analysis identify novel yeast genes affecting ethyl acetate production, a non-selectable polygenic trait. Microbial Cell 3(4): 159-175. doi: 10.15698/mic2016.04.491
© 2016 Abt et al. This is an open-access article released under the terms of the Creative Commons Attribution (CC BY) license, which allows the unrestricted use, distribution, and reproduction in any medium, provided the original author and source are acknowledged.
Abstract:
Isolation of mutants in populations of microorganisms has been a valuable tool in experimental genetics for decades. The main disadvantage, however, is the inability of isolating mutants in non-selectable polygenic traits. Most traits of organisms, however, are non-selectable and polygenic, including industrially important properties of microorganisms. The advent of powerful technologies for polygenic analysis of complex traits has allowed simultaneous identification of multiple causative mutations among many thousands of irrelevant mutations. We now show that this also applies to haploid strains of which the genome has been loaded with induced mutations so as to affect as many non-selectable, polygenic traits as possible. We have introduced about 900 mutations into single haploid yeast strains using multiple rounds of EMS mutagenesis, while maintaining the mating capacity required for genetic mapping. We screened the strains for defects in flavor production, an important non-selectable, polygenic trait in yeast alcoholic beverage production. A haploid strain with multiple induced mutations showing reduced ethyl acetate production in semi-anaerobic fermentation, was selected and the underlying quantitative trait loci (QTLs) were mapped using pooled-segregant whole-genome sequence analysis after crossing with an unrelated haploid strain. Reciprocal hemizygosity analysis and allele exchange identified PMA1 and CEM1 as causative mutant alleles and TPS1 as a causative genetic background allele. The case of CEM1 revealed that relevant mutations without observable effect in the haploid strain with multiple induced mutations (in this case due to defective mitochondria) can be identified by polygenic analysis as long as the mutations have an effect in part of the segregants (in this case those that regained fully functional mitochondria). Our results show that genomic saturation mutagenesis combined with complex trait polygenic analysis could be used successfully to identify causative alleles underlying many non-selectable, polygenic traits in small collections of haploid strains with multiple induced mutations.
doi: 10.15698/mic2016.04.491
Volume 3, pp. 159 to 175, published 18/03/2016.