Arabidopsisand relatives as models for the study of genetic and genomic incompatibilities

Abstract

The past few years have seen considerable advances in speciation research, but whether drift or adaptation is more likely to lead to genetic incompatibilities remains unknown. Some of the answers will probably come from not only studying incompatibilities between well-established species, but also from investigating incipient speciation events, to learn more about speciation as an evolutionary process. The genus Arabidopsis, which includes the widely used Arabidopsis thaliana, provides a useful set of model species for studying many aspects of population divergence. The genus contains both self-incompatible and incompatible species, providing a platform for studying the impact of mating system changes on genetic differentiation. Another important path to plant speciation is via formation of polyploids, and this can be investigated in the young allotetraploid species A. arenosa. Finally, there are many cases of intraspecific incompatibilities in A. thaliana, and recent progress has been made in discovering the genes underlying both F 1 and F 2 breakdown. In the near future, all these studies will be greatly empowered by complete genome sequences not only for all members of this relatively small genus, but also for many different individuals within each species.

The ARC1 E3 Ligase Gene Is Frequently Deleted in Self-Compatible Brassicaceae Species and Has a Conserved Role in Arabidopsis lyrata Self-Pollen Rejection

“…The breakdown of self-incompatibility in C. rubella occurred ;30,000 to 50,000 years ago (Foxe et al, 2009;Guo et al, 2009), while the breakdown of self-incompatibility of A. thaliana has been estimated to be much more distant, between ;400,000 and 1 million years ago Tang et al, 2007;Bomblies and Weigel, 2010). The speciation of C. rubella and the transition to a self-pollinating species was also a direct result of a population bottleneck, and the inactivation of the SCR/SP11-SRK genes was likely the initial event that allowed self-pollination to occur (Foxe et al, 2009;Guo et al, 2009).…”

Speciation genetics: current status and evolving approaches

“…A number of in vitro experiments have demonstrated that fitness trade-offs between heterogeneous environments are easy to achieve and can be stably maintained (Rainey & Travisano 1998;Buckling et al 2009). The genes involved in adaptations can potentially be mapped and in recent years it has become possible to monitor the evolution of whole viral and prokaryotic genomes and this will likely be increasingly feasible in eukaryotes (Bomblies & Weigel 2010). From these studies it emerges that ecological adaptations often seem to entail lowered hybrid fitness between divergent lineages by negative epistatic interactions sensu BDM incompatibilities (Dettman et al 2007;Duffy et al 2007;Barrick et al 2009).…”

“…With the availability of larger marker sets one could anticipate that mapping efforts will be focused on other methods, such as association scans (linkage disequilibrium mapping) using population samples, an approach most well developed in model species with the available genome sequences (Nordborg & Weigel 2008;Goddard & Hayes 2009;Bomblies & Weigel 2010). In divergent natural populations or hybrid zones, it may be of particular interest to make use of the extended linkage disequilibrium resulting from the admixture of differentiated populations (Rieseberg & Buerkle 2002;Smith & O'Brien 2005).…”

What role does natural selection play in speciation?

“…The isolation that ensues may be related to the process that was selected or may be due to an entirely different pathway (e.g. autoimmunity in plants (Bomblies & Weigel, 2010), nucleoporins in Drosophila, melanomas in fish (Orr & Presgraves 2000)). Divergence might be due to random drift across a neutral adaptive landscape (Gavrilets & Gravner 1997;Gavrilets 2004), or in opposition to weak selection (e.g.…”