Abstract
Fusarium is a diverse assemblage that includes a large number of species of considerable medical and agricultural importance. Not surprisingly, whole genome sequences for many Fusarium species have been published or are in the process of being determined, the availability of which is invaluable for deciphering the genetic basis of key phenotypic traits. Here we investigated the distribution, genic composition, and evolutionary history of a locus potentially determining growth rate in the pitch canker pathogen F. circinatum. We found that the genomic region underlying this locus is highly conserved amongst F. circinatum and its close relatives, except for the presence of a 12 000 base pair insertion in all of the examined isolates of F. circinatum. This insertion encodes for five genes and our phylogenetic analyses revealed that each was most likely acquired through horizontal gene transfer from polyphyletic origins. Our data further showed that this region is located in a region low in G+C content and enriched for repetitive sequences and transposable elements, which is situated near the telomere of Chromosome 3 of F. circinatum. As have been shown for other fungi, these findings thus suggest that the emergence of the unique 12 000 bp region in F. circinatum is linked to the dynamic evolutionary processes associated with subtelomeres that, in turn, have been implicated in the ecological adaptation of fungal pathogens.
Highlights
Fusarium species are remarkably diverse (Leslie & Summerell 2006, O’Donnell et al 2013)
Relative to the overall phylogenetic relationships among the F. fujikuroi species complex (FFSC) species and its Fusarium relatives, we investigated the relationships between the F. circinatumVSHFL¿F JHQHV HQFRGHG LQ WKH $7$&EKFRQWDLQLQJ region to those encoded elsewhere in the examined Fusarium genomes (Supplementary Table S3)
The results of this study showed that the QTL-marker AT/AC 625bh, which previously had been associated with growth rate (De Vos et al 2011), is located on Chromosome 3 of F. circinatum
Summary
Fusarium species are remarkably diverse (Leslie & Summerell 2006, O’Donnell et al 2013). In addition to the telomeres and centromeres (Chiara et al 2015, Sperschneider et al 2015), areas of high sequence variability occur in other chromosomal regions and may even extend across entire chromosomes such as the supernumerary or dispensable chromosomes (Ma et al 2010, Van der Nest et al 2014) These variable regions in diverse fungi are rich in repeats and transposable elements (TEs), have G+C contents that differ markedly from the rest of the genome (Goodwin et al 2011), and often encode nonessential genes (Fedorova et al 2008, Coleman et al 2009, Sperschneider et al 2015). Overall, such regions of variability are thought to accelerate genome evolution and plasticity and to promote adaptation (Fedorova et al 2008, Coleman et al 2009, Chiara et al 2015)
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