Transmission ratio distortion in Arabidopsis lyrata: effects of population divergence and the S-locus

Abstract

We investigated transmission ratio distortion within an Icelandic population of Arabidopsis lyrata using 16 molecular markers unlinked to the S-locus. Transmission ratio distortion was found more often than expected by chance at the gametic level, but not at the genotypic or zygotic level. The gametic effect may be due to meiotic drive or selection acting postmeiotically. At the gametic level, 10.9% of the tests were significant, which is substantially lower than earlier observed in an interpopulation cross (allowing for differences in power)-suggesting that the high level of transmission ratio distortion in the interpopulation cross is due to population divergence. It is also substantially lower than previously observed in intrapopulation crosses at the self-incompatibility locus, suggesting inherent fitness differences of the selfincompatibility alleles. We discuss the possible role of deleterious alleles accumulating at loci under balancing selection. Zygotic effects play a larger role in the interpopulation cross than in the intrapopulation crosses suggesting that Dobzhansky-Muller incompatibilities may be accumulating between the widely diverged populations.

The recombination landscape in Arabidopsis thaliana F2 populations

“…In Silene latifolia, a dioecious plant, the 3:1 sex ratio bias between females and males may be the result of pollen competition between X-bearing and Y-bearing pollen (Taylor and Ingvarsson, 2003). In Arabidopsis lyrata, several cases of segregation distortion have been reported, and most were due to gametic effects (Leppala et al, 2008). In addition, diversity at the self-incompatibility S locus in A. lyrata drives strong distortion between incompatible alleles.…”

Genetic linkage map for Amylostereum areolatum reveals an association between vegetative growth and sexual and self-recognition

“…Larraya et al (2001) also hypothesized that balancing selection acting on the recognition loci of P. ostreatus provides a possible explanation for the segregation distortion observed at the mat loci of this fungus. This is because balancing selection, which is thought to maintain the highly polymorphic multi-allelic nature of the recognition loci and the even distribution and long persistence of alleles in populations (Meyer and Thomsen, 2001), also results in the maintenance of potentially deleterious mutations in a population that would otherwise have been lost due to negative selection (Leppälä et al, 2008). Thus, balancing selection will prevent the loss of alleles associated with slow growth resulting in segregation distortion of these alleles.…”

“…The presence of alleles for slow growth at the het loci, which are known to encode genes involved in housekeeping and other functions (Saupe, 2000), would therefore influence the fitness of individuals negatively. In the case of the mat loci, balancing selection could also affect genes that play no apparent role in mating but that have become entrapped at the mat loci (e.g., Uyenoyama, 2005;Leppälä et al, 2008). This is especially true as some of them encode proteins vital for growth such as ketopantoate reductase involved in energy metabolism and that is encoded at the agaricomycetes mat-A locus (James et al, 2004;Niculita-Hirzel et al, 2008).…”

“…This entailed construction of a genetic linkage map for A. areolatum and positioning of its recognition loci, as have been done for other eukaryotes (e.g., Kubisiak and Milgroom, 2006;Lind et al, 2007;Leppälä et al, 2008). For this purpose we used amplified fragment length polymorphisms (AFLPs) (Vos et al, 1995) for map construction and AFLPbased bulked segregant analysis (BSA) to identify markers closely linked to the recognition loci.…”

The Sheltered Genetic Load Linked to the S Locus in Plants: New Insights From Theoretical and Empirical Approaches in Sporophytic Self-Incompatibility

“…Dowd et al (2000) indeed found only 13 genes near the S locus in Petunia inflata. However, two studies have demonstrated the existence of transmission ratio distortion of some S alleles in A. lyrata (Bechsgaard et al 2004;Leppala et al 2008). The authors proposed that this could be indirect evidence of the existence of a sheltered load.…”