Killer meiotic driver prevents chromosome loss and enhances fitness in a fungal pathogen
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…
Fungal pathogens commonly carry non-essential chromosomes, known as dispensable chromosomes (DCs), which provide a selective advantage in challenging environments or during infection. However, the mechanism behind the preservation of these DCs during evolution is not well understood. Researchers have discovered that a meiotic driver called Spore Killer (spok), located on a large transposon called Starship, plays a crucial role in maintaining a specific DC in the fungal pathogen Fusarium oxysporum.
When a functional spok gene is introduced to a mitotically unstable DC, the rate of spontaneous loss of the DC is significantly reduced. Moreover, deletion of the spok gene from a DC that is normally maintained by the fungus leads to an increased frequency of DC loss. Competition experiments between isogenic strains carrying either a functional or a killing-deficient spok allele demonstrated that the presence of a functional spok results in a substantial fitness advantage for the fungal host.
This enhanced fitness is dependent on the transmission of spok through hyphal fusion, indicating that the killing activity of Spok is essential for its beneficial effects.
Overall, the study highlights the role of Spok and its Starship carrier in helping fungal pathogens maintain their DCs, thereby preserving metabolic and pathogenic plasticity over the long term.
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