Transition to Self-compatibility Associated With Dominant S-allele in a Diploid Siberian Progenitor of Allotetraploid Arabidopsis kamchatica Revealed by Arabidopsis lyrata Genomes

A transition to selfing can be beneficial when mating partners are scarce, for example, due to ploidy changes or at species range edges. Here, we explain how self-compatibility evolved in diploid Siberian Arabidopsis lyrata, and how it contributed to the establishment of allotetraploid Arabidopsis kamchatica. First, we provide chromosome-level genome assemblies for two self-fertilizing diploid A. lyrata accessions, one from North America and one from Siberia, including a fully assembled S-locus for the latter. We then propose a sequence of events leading to the loss of self-incompatibility in Siberian A. lyrata, date this independent transition to & SIM;90 Kya, and infer evolutionary relationships between Siberian and North American A. lyrata, showing an independent transition to selfing in Siberia. Finally, we provide evidence that this selfing Siberian A. lyrata lineage contributed to the formation of the allotetraploid A. kamchatica and propose that the selfing of the latter is mediated by the loss-of-function mutation in a dominant S-allele inherited from A. lyrata.

Automated summary

A transition to selfing can be advantageous in situations with limited mating partners. This study investigates the evolution of self-compatibility in diploid Siberian Arabidopsis lyrata and its contribution to the formation of allotetraploid Arabidopsis kamchatica. The researchers provide genome assemblies for two self-fertilizing diploid A. lyrata accessions and propose a sequence of events leading to the loss of self-incompatibility in Siberian A. lyrata, dating this transition to around 90,000 years ago. They also demonstrate the independent transition to selfing in Siberia and suggest that the selfing of A. kamchatica is mediated by a loss-of-function mutation in a dominant S-allele inherited from A. lyrata.