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Variation in gene content of a dispensable chromosome in members of the Fusarium fujikuroi species complex

Lieschen de Vos: Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

<div>Members of the <em>Fusarium fujikuroi</em> species complex (FFSC) include important plant pathogens and mycotoxin-producing fungi that have a haploid chromosome number of 12. The smallest chromosome is dispensable, and evidence indicates that it varies among species and even strains of individual species. Whole-genome assemblies of <em>Fusarium </em>species representing the ten well-known mating populations were compared to identify scaffolds corresponding to chromosome 12. Shared and unique genes amongst the different species were determined using a reciprocal BLASTp approach. Chromosome 12 from different species exhibited significant length polymorphism compared to other chromosomes, and displayed remarkably low levels of sequence homology and synteny. Similarity in gene content and organization appeared to be limited to closely related species in each of the three main clades of FFSC. Phylogenetic analyses of the genes on chromosome 12 homologs indicated that most had diverse and non-orthologous origins. Species-specific unique genes were dispersed throughout the chromosome, with no clustering. The low sequence and genic homology, as well as the diverse evolutionary trajectories of genes present on chromosome 12 highlights the plasticity of this chromosome. Our future work will investigate the roles that these molecules play in the biology of this important group of fungi.</div>