Aneuploidy in yeast: Segregation error or adaptation mechanism?

• Published in: Yeast (Chichester, England) England), 2019-09, Vol.36 (9), p.525-539
• Main Authors: Gilchrist, Ciaran, Stelkens, Rike
• Format: Article
• Language: English
• Subjects: adaptation; Aneuploidy; Budding Topic; Cell death; Chromosomes; Environmental stress; Gene dosage; Genetic crosses; Genetic disorders; Genomes; hybridisation; Hybridization; Meiosis; yeast
• ISSN: 0749-503X; 1097-0061; 1097-0061
• DOI: 10.1002/yea.3427

Aneuploidy is the loss or gain of chromosomes within a genome. It is often detrimental and has been associated with cell death and genetic disorders. However, aneuploidy can also be beneficial and provide a quick solution through changes in gene dosage when cells face environmental stress. Here, we review the prevalence of aneuploidy in Saccharomyces, Candida, and Cryptococcus yeasts (and their hybrid offspring) and analyse associations with chromosome size and specific stressors. We discuss how aneuploidy, a segregation error, may in fact provide a natural route for the diversification of microbes and enable important evolutionary innovations given the right ecological circumstances, such as the colonisation of new environments or the transition from commensal to pathogenic lifestyle. We also draw attention to a largely unstudied cross link between hybridisation and aneuploidy. Hybrid meiosis, involving two divergent genomes, can lead to drastically increased rates of aneuploidy in the offspring due to antirecombination and chromosomal missegregation. Because hybridisation and aneuploidy have both been shown to increase with environmental stress, we believe it important and timely to start exploring the evolutionary significance of their co‐occurrence. Aneuploidy is usually detrimental for the cell, but it can provide a rapid adaptive fix when populations face environmental stress. We also know that hybridisation‐the mating between different species or strains‐drastically increases aneuploidy due to meiotic failure. We argue that it is time to put our knowledge about these processes in an evolutionary context. The temporal and spatial overlap of stress, hybridisation, and aneuploidy may lead to the spread of aneuploid genomes, if only as a transient solution to adaptation, facilitating the evolution of hybrid microbial populations with new ecological characteristics, for example, drug resistance or increased infectivity.