Causes and Consequences of Genome Expansion in Fungi

Department of Ecology and Evolutionary Biology, Yale University, USA.
Genome Biology and Evolution (Impact Factor: 4.23). 11/2011; 4(1):13-23. DOI: 10.1093/gbe/evr124
Source: PubMed


Fungi display a large diversity in genome size and complexity, variation that is often considered to be adaptive. But because nonadaptive processes can also have important consequences on the features of genomes, we investigated the relationship of genetic drift and genome size in the phylum Ascomycota using multiple indicators of genetic drift. We detected a complex relationship between genetic drift and genome size in fungi: genetic drift is associated with genome expansion on broad evolutionary timescales, as hypothesized for other eukaryotes; but within subphyla over smaller timescales, the opposite trend is observed. Moreover, fungi and bacteria display similar patterns of genome degradation that are associated with initial effects of genetic drift. We conclude that changes in genome size within Ascomycota have occurred using two different routes: large-scale genome expansions are catalyzed by increasing drift as predicted by the mutation-hazard model of genome evolution and small-scale modifications in genome size are independent of drift.

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Available from: Yogeshwar D Kelkar, Nov 04, 2014
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    • "The A. ochraceoroseus genome contained 18 putative SM clusters and the A. rambellii genome contained 20 putative SM clusters. It has been postulated that high genetic drift, coupled with deletions, in eukaryotes refines their genomes by removing regions that are not integral to the organism's survival (Kelkar and Ochman, 2012). "
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    • "In a recent analysis of the underlying processes associated with genome size expansion within the Ascomycota, Kelkar and Ochman (2012) suggest that genetic drift, reflected through a decrease in gene density and a proliferation of introns, has played a significant role across many lineages on broad evolutionary time scales. The large genome size of C. geophilum might therefore result from ancestral genome size expansion driven by genetic drift, which would lead to a repeat-rich and relatively gene-poor genome. "
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