title: Adaptation to drought in two wild tomato species: the evolution of the Asr gene family.
abstract: Wild tomato species are a valuable system in which to study local adaptation to drought: they grow in diverse environments ranging from mesic to extremely arid conditions. Here, we investigate the evolution of members of the Asr (ABA/water stress/ripening induced) gene family, which have been reported to be involved in the water stress response. We analysed molecular variation in the Asr gene family in populations of two closely related species, Solanum chilense and Solanum peruvianum. We concluded that Asr1 has evolved under strong purifying selection. In contrast to previous reports, we did not detect evidence for positive selection at Asr2. However, Asr4 shows patterns consistent with local adaptation in an S. chilense population that lives in an extremely dry environment. We also discovered a new member of the gene family, Asr5. Our results show that the Asr genes constitute a dynamic gene family and provide an excellent example of tandemly arrayed genes that are of importance in adaptation. Taking the potential distribution of the species into account, it appears that S. peruvianum can cope with a great variety of environmental conditions without undergoing local adaptation, whereas S. chilense undergoes local adaptation more frequently.
authors.affiliation: Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Fischer
authors.affiliation: CIRAD, Biological System Department - Research Unit 39 'Genetic Diversity and Breeding of Forest Tree Species', Campus international de Baillarguet TA A-39/C, 34398 Montpellier Cedex 5, France.
authors.forename: Létizia
authors.initials: L
authors.lastname: Camus-Kulandaivelu
authors.affiliation: CIRAD, Biological System Department - Research Unit 39 'Genetic Diversity and Breeding of Forest Tree Species', Campus international de Baillarguet TA A-39/C, 34398 Montpellier Cedex 5, France.
authors.forename: François
authors.initials: F
authors.lastname: Allal
authors.affiliation: Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Stephan
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D055864:Droughts; D017753:Ecosystem; D019143:Evolution, Molecular; D017343:Genes, Plant; D054643:INDEL Mutation; D005810:Multigene Family; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D032322:Solanum / Q000235:genetics* / Q000502:physiology