A goal of speciation genetics is to understand how the genetic components underlying interspecific reproductive barriers originate within species. Unilateral incompatibility (UI) is a postmating prezygotic barrier in which pollen rejection in the female reproductive tract (style) occurs in only one direction of an interspecific cross. Natural variation in the strength of UI has been observed among populations within species in the wild tomato clade. In some cases, molecular loci underlying self-incompatibility (SI) are associated with this variation in UI, but the mechanistic connection between these intra- and inter-specific pollen rejection behaviors is poorly understood in most instances. We generated an F2 population between SI and SC genotypes of a single species, Solanum pennellii, to examine the genetic basis of intraspecific variation in UI against other species, and to determine whether loci underlying SI are genetically associated with this variation. We found that F2 individuals vary in the rate at which UI rejection occurs. One large effect QTL detected for this trait co-localized with the SI-determining S-locus. Moreover, individuals that expressed S-RNase-the S-locus protein involved in SI pollen rejection-in their styles had much more rapid UI responses compared with those without S-RNase protein. Our analysis shows that intraspecific variation at mate choice loci-in this case at loci that prevent self-fertilization-can contribute to variation in the expression of interspecific isolation, including postmating prezygotic barriers. Understanding the nature of such intraspecific variation can provide insight into the accumulation of these barriers between diverging lineages.
Keywords: S-locus; QTL; postmating prezygotic; reproductive isolation; self-compatibility; speciation; tomato; unilateral incompatibility.
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Two Loci Contribute Epistastically to Heterospecific Pollen Rejection, a Postmating Isolating Barrier Between Species.G3 (Bethesda). 2017 Jul 5;7(7):2151-2159. doi: 10.1534/g3.117.041673. G3 (Bethesda). 2017. PMID: 28512086 Free PMC article.
Molecular mechanisms of postmating prezygotic reproductive isolation uncovered by transcriptome analysis.Mol Ecol. 2016 Jun;25(11):2592-608. doi: 10.1111/mec.13679. Epub 2016 May 30. Mol Ecol. 2016. PMID: 27136303
Multiple features that distinguish unilateral incongruity and self-incompatibility in the tomato clade.Plant J. 2010 Nov;64(3):367-78. doi: 10.1111/j.1365-313X.2010.04340.x. Epub 2010 Oct 1. Plant J. 2010. PMID: 20804455
Interspecific reproductive barriers in the tomato clade: opportunities to decipher mechanisms of reproductive isolation.Sex Plant Reprod. 2011 Sep;24(3):171-87. doi: 10.1007/s00497-010-0155-7. Epub 2010 Nov 14. Sex Plant Reprod. 2011. PMID: 21076968 Review.
Compatibility and incompatibility in S-RNase-based systems.Ann Bot. 2011 Sep;108(4):647-58. doi: 10.1093/aob/mcr179. Epub 2011 Jul 28. Ann Bot. 2011. PMID: 21803740 Free PMC article. Review.