Polyploidy in fungi: evolution after whole-genome duplication

Abstract

Polyploidy is a major evolutionary process in eukaryotes-particularly in plants and, to a less extent, in animals, wherein several past and recent whole-genome duplication events have been described. Surprisingly, the incidence of polyploidy in other eukaryote kingdoms, particularly within fungi, remained largely disregarded by the scientific community working on the evolutionary consequences of polyploidy. Recent studies have significantly increased our knowledge of the occurrence and evolutionary significance of fungal polyploidy. The ecological, structural and functional consequences of polyploidy in fungi are reviewed here and compared with the knowledge acquired with conventional plant and animal models. In particular, the genus Saccharomyces emerges as a relevant model for polyploid studies, in addition to plant and animal models.

Figure 1.

Annual proportion of publications addressing polyploidy within the Saccharomyces genus. The annual number of publications addressing either ‘Saccharomyces tetraploid OR polyploid’ or ‘Saccharomyces haploid OR diploid -tetraploid -polyploid’ was estimated using Google Scholar (release of May 2011).

Figure 2.

Inferred polyploidy and reticulate evolution in the Chromalveolata eukaryote supergroup. Schematic phylogeny and classification of the Chromalveolata eukaryote supergroup base on the taxonomy database maintained by the UniProt group newt [18] (release of May 2011). Branch lengths are not proportional to genetic distances. Red circles indicate suspected polyploidy. Full references are available in electronic supplementary material, table S4.

Figure 3.

Inferred polyploidy and reticulate evolution in fungi. Schematic phylogeny and classification of the fungi, based on Hibbet et al. [19]. Red circles indicate suspected polyploidy, blue squares indicate lineages with individuals having hybrid origin (reticulate evolution). Branch lengths are not proportional to genetic distances. Full references are available in electronic supplementary material, tables S1 and S2.

Figure 4.

The parasexual cycle of Candida albicans.

Figure 5.

Polyploid genomes of Nicotiana tabacum and Saccharomyces pastorianus. The schematic genomes illustrate the parental origin of the chromosomes. The different types of chromosomes are drawn. Black circles represent centromere position. The structure of N. tabacum genome was adapted from Chester et al. [48] and displayed eight inter-genomic rearrangements. For S. pastorianus, Nakao et al. [41] identified 10 inter-genomic rearrangements and six intra-genomic translocations between chromosomes II–IV and VIII–XV (S. bayanus-like subgenome, now identified as S. eubayanus) and V–XI and XI–XV (S. cerevisiae subgenome).