Combinations of Spok genes create multiple meiotic drivers in Podospora

Area of Science:

• Genetics
• Evolutionary Biology
• Mycology

Background:

• Meiotic drive, the unequal inheritance of alleles, manifests as spore killing in fungi.
• Seven spore killer types (Psk) have been identified in natural populations of Podospora anserina.
• The genetic basis of these spore killer types remained largely unknown.

Purpose of the Study:

• To elucidate the genetic underpinnings of spore killer types in Podospora anserina.
• To identify the genes responsible for meiotic drive and spore killing.
• To understand the evolutionary mechanisms of meiotic drive genes.

Main Methods:

• Classical genetic analyses were used to identify spore killer types.
• Gene identification and characterization of Spok homologs within a defined Spok block.
• Genomic and phylogenetic analyses across ascomycetes.

Main Results:

• The Spok gene family underlies the Psk types in Podospora anserina.
• The combination and chromosomal location of Spok genes determine specific spore killer types and create a killing hierarchy.
• Two novel Spok homologs were identified within a large, variable Spok block.
• The SPOK protein possesses both killing and resistance functions, mediated by distinct nuclease and kinase domains.
• Spok genes likely disperse via cross-species transfer and evolve through duplication and diversification.

Conclusions:

• The Spok gene family is the key determinant of meiotic drive and spore killing phenotypes in Podospora anserina.
• Spok gene evolution involves horizontal gene transfer and intragenomic duplication/diversification.
• Understanding Spok gene function and evolution provides insights into meiotic drive mechanisms in fungi.