Killer meiotic driver prevents chromosome loss and enhances fitness in a fungal pathogen

Authors

Puebla-Planas, G., Doddi, A., Ayhan, D. H., Gutierrez-Escribano, P., Ma, L.-J., Lopez-Berges, M. S., Di Pietro, A.

Abstract

Fungal pathogens often carry dispensable chromosomes (DCs) that confer a selective advantage in adverse environments or during host infection but can be spontaneously lost under non-selective conditions. How DCs are maintained in evolving populations remains poorly understood. Here we show that a meiotic driver known as Spore Killer (spok), located on a giant Starship transposon, limits spontaneous loss of a conserved DC in the cross-kingdom pathogen Fusarium oxysporum. Transfer of a functional spok gene, but not of a killing-deficient mutant allele, to a mitotically unstable DC significantly reduced its loss rate, while spok deletion from a stably maintained DC increased loss frequency. Competition experiments between isogenic strains carrying a functional or a killing-deficient spok allele revealed a dramatic fitness gain conferred by Spok killing activity, which required transmission by hyphal fusion. Thus, spoks and their Starship carriers benefit fungal hosts by preventing DC loss and preserving long-term metabolic and pathogenic plasticity.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 06 Oct 2026.

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