Sexual transmission of the [Het-S] prion leads to meiotic drive in Podospora anserina.
In the filamentous fungus Podospora anserina, two phenomena are associated with polymorphism at the het-s locus, vegetative incompatibility and ascospore abortion. Two het-s alleles occur naturally, het-s and het-S. The het-s encoded protein is a prion propagating as a self-perpetuating amyloid aggregate. When prion-infected [Het-s] hyphae fuse with [Het-S] hyphae, the resulting heterokaryotic cells necrotize. [Het-s] and [Het-S] strains are sexually compatible. When, however, a female [Het-s] crosses with [Het-S], a significant percentage of het-S spores abort, in a way similar to spore killing in Neurospora and Podospora. We report here that sexual transmission of the [Het-s] prion after nonisogamous mating in the reproductive cycle of Podospora is responsible for the killing of het-S spores. Progeny of crosses between isogenic strains with distinct wild-type or introduced, ectopic het-s/S alleles were cytologically and genetically analyzed. The effect of het-s/S overexpression, ectopic het-s/S expression, absence of het-s expression, loss of [Het-s] prion infection, and the distribution patterns of HET-s/S-GFP proteins were categorized during meiosis and ascospore formation. This study unveiled a het-S spore-killing system that is governed by dosage of and interaction between the [Het-s] prion and the HET-S protein. Due to this property of the [Het-s] prion, the het-s allele acts as a meiotic drive element favoring maintenance of the prion-forming allele in natural populations.
Laboratory of Genetics, Wageningen University, Arboretumlaan 4, The Netherlands. Henk.Dalstra@wur.nl
Henk J P
HJ
Dalstra
Klaas
K
Swart
Alfons J M
AJ
Debets
Sven J
SJ
Saupe
Rolf F
RF
Hoekstra
D001203:Ascomycota / Q000166:cytology*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D008540:Meiosis / Q000502:physiology*; D008856:Microscopy, Fluorescence
D005656:Fungal Proteins; C083891:HET-S protein, Podospora anserina