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Open AccessArticle

Repeat-Induced Point Mutations Drive Divergence between Fusarium circinatum and Its Close Relatives

Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa
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Authors contributed equally.
Pathogens 2019, 8(4), 298; https://doi.org/10.3390/pathogens8040298
Received: 22 November 2019 / Revised: 6 December 2019 / Accepted: 9 December 2019 / Published: 14 December 2019
(This article belongs to the Special Issue Biological Systematics of Tree Pathogenic Fungi)
The Repeat-Induced Point (RIP) mutation pathway is a fungal-specific genome defense mechanism that counteracts the deleterious effects of transposable elements. This pathway permanently mutates its target sequences by introducing cytosine to thymine transitions. We investigated the genome-wide occurrence of RIP in the pitch canker pathogen, Fusarium circinatum, and its close relatives in the Fusarium fujikuroi species complex (FFSC). Our results showed that the examined fungi all exhibited hallmarks of RIP, but that they differed in terms of the extent to which their genomes were affected by this pathway. RIP mutations constituted a large proportion of all the FFSC genomes, including both core and dispensable chromosomes, although the latter were generally more extensively affected by RIP. Large RIP-affected genomic regions were also much more gene sparse than the rest of the genome. Our data further showed that RIP-directed sequence diversification increased the variability between homologous regions of related species, and that RIP-affected regions can interfere with homologous recombination during meiosis, thereby contributing to post-mating segregation distortion. Taken together, these findings suggest that RIP can drive the independent divergence of chromosomes, alter chromosome architecture, and contribute to the divergence among F. circinatum and other members of this economically important group of fungi. View Full-Text
Keywords: Fusarium circinatum; lineage divergence; RIP; Repeat-Induced Point mutations; segregation distortion; genome evolution Fusarium circinatum; lineage divergence; RIP; Repeat-Induced Point mutations; segregation distortion; genome evolution
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van Wyk, S.; Wingfield, B.D.; De Vos, L.; van der Merwe, N.A.; Santana, Q.C.; Steenkamp, E.T. Repeat-Induced Point Mutations Drive Divergence between Fusarium circinatum and Its Close Relatives. Pathogens 2019, 8, 298.

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