Pathogenicity chromosomes in Fusarium oxysporum

Jiming Li Peter van Dam Mara de Sain Martijn Rep
Molecular Plant Pathology, University of Amsterdam, Amsterdam, Netherlands

Tomato-infecting strains Fusarium oxysporum f.sp. lycopersici (Fol) contain pathogenicity chromosomes. These chromosomes determine host range and can be transferred to a non-pathogenic strain, turning the recipient strain into a pathogen [1]. Surprisingly, loss of a big part of the pathogenicity chromosome in a strain of Fol does not affect virulence [2]. To investigate which parts of the chromosome in Fol are required for pathogenicity to tomato plants and which parts can be transferred, we labeled several positions of the pathogenicity chromosome in Fol with different marker genes (encoding green fluorescence and red fluorescence). We then used fluorescence-assisted cell sorting (FACS) to select spores that have lost green fluorescence or red fluorescence and thus obtained several lines with a variety of deletions in this chromosome. We are currently testing virulence of these lines and aim to perform horizontal chromosome transfer experiments to assess whether these partial chromosomes can be transferred. Finally, we aim to characterize the pathogenicity chromosome of a strain that is specific to melon -Fusarium oxysporum f.sp. melonis (Fom)- and compare this to the previously identified pathogenicity chromosome of Fusarium oxysporum f.sp. radicis-cucumerinum (Forc), a strain that has a broad host range (cucurbits). We want to identify the regions or genes in Forc and Fom that are responsible for the difference in host range.

[1] Ma, L. J., et al. (2010). "Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium." Nature 464(7287): 367-373.

[2] Vlaardingerbroek, I., et al. (2016). "Dispensable chromosomes in Fusarium oxysporum f. sp. lycopersici." Mol Plant Pathol 17(9): 1455-1466.