Abstract
Meiotic drivers are genetic elements that break Mendel's law of segregation to be transmitted into more than half of the offspring produced by a heterozygote. The success of a driver relies on outcrossing (mating between individuals from distinct lineages) because drivers gain their advantage in heterozygotes. It is, therefore, curious that Schizosaccharomyces pombe, a species reported to rarely outcross, harbors many meiotic drivers. To address this paradox, we measured mating phenotypes in S. pombe natural isolates. We found that the propensity for cells from distinct clonal lineages to mate varies between natural isolates and can be affected both by cell density and by the available sexual partners. Additionally, we found that the observed levels of preferential mating between cells from the same clonal lineage can slow, but not prevent, the spread of a wtf meiotic driver in the absence of additional fitness costs linked to the driver. These analyses reveal parameters critical to understanding the evolution of S. pombe and help explain the success of meiotic drivers in this species.
Highlights
Mating behaviours have long been a focus of art, literature, and formal scientific inquiry
Outcrossing can be beneficial because it can help purge deleterious alleles from a line of descent, but it can be costly as it can promote the spread of selfish genes (Burt and Trivers 1998; Crow 1988; Hurst and Werren 2001; McDonald et al 2016; Zeyl et al 1996). 44 Meiotic drivers represent one type of selfish genetic element that relies on outcrossing 45 to persist and spread in a population (Lindholm et al 2016; Novitski 1957)
Population genetic analyses of one homothallic fungus, Sclerotinia sclerotiorum, supports that homothallism is compatible with frequent outcrossing (Attanayake et al 2014). 92 Very little is known about the ecology of S. pombe in the wild, including how often S. 93 pombe cells outcross (Jeffares et al 2018)
Summary
Mating behaviours have long been a focus of art, literature, and formal scientific inquiry. Mating in S. pombe is widely thought to preferentially occur between daughter cells clonally derived from a common progenitor via a recent mitotic division, which we refer to as ‘same-clone mating’ (Figure 1-figure supplement 1B; Egel 1977; Gutz and Doe 1975; Miyata and Miyata 1981; Billiard et al 2012; Perrin 2011) The support for this idea is 65 described below. Recombination rates are inextricably linked to the complex drive landscape because the presence of drivers affects the recombination rate within viable offspring, independent of chromosomal rearrangements (Bravo Nunez et al 2020b)
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