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Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix.

ABSTRACT: BACKGROUND:Life history traits like developmental time, age and size at maturity are directly related to fitness in all organisms and play a major role in adaptive evolution and speciation processes. Comparative genomic or transcriptomic approaches to identify positively selected genes involved in species divergence can help to generate hypotheses on the driving forces behind speciation. Here we use a bottom-up approach to investigate this hypothesis by comparative analysis of orthologous transcripts of four closely related European Radix species. RESULTS:Snails of the genus Radix occupy species specific distribution ranges with distinct climatic niches, indicating a potential for natural selection driven speciation based on ecological niche differentiation. We then inferred phylogenetic relationships among the four Radix species based on whole mt-genomes plus 23 nuclear loci. Three different tests to infer selection and changes in amino acid properties yielded a total of 134 genes with signatures of positive selection. The majority of these genes belonged to the functional gene ontology categories "reproduction" and "genitalia" with an overrepresentation of the functions "development" and "growth rate". CONCLUSIONS:We show here that Radix species divergence may be primarily enforced by selection on life history traits such as (larval-) development and growth rate. We thus hypothesise that life history differences may confer advantages under the according climate regimes, e.g., species occupying warmer and dryer habitats might have a fitness advantage with fast developing susceptible life stages, which are more tolerant to habitat desiccation.

SUBMITTER: Feldmeyer B

PROVIDER: S-EPMC4539673 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix.

Feldmeyer Barbara B Greshake Bastian B Funke Elisabeth E Ebersberger Ingo I Pfenninger Markus M

BMC evolutionary biology 20150819

<h4>Background</h4>Life history traits like developmental time, age and size at maturity are directly related to fitness in all organisms and play a major role in adaptive evolution and speciation processes. Comparative genomic or transcriptomic approaches to identify positively selected genes involved in species divergence can help to generate hypotheses on the driving forces behind speciation. Here we use a bottom-up approach to investigate this hypothesis by comparative analysis of orthologou ...[more]

PMID: 26281847

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Project description:BackgroundNod26-like intrinsic proteins (NIPs) that belong to the aquaporin superfamily are unique to plants. According to homology modeling and phylogenetic analysis, the NIP subfamily can be further divided into three subgroups with distinct biological functions (NIP I, NIP II, and NIP III). In some grasses, the NIP III subgroup proteins (NIP2s) were demonstrated to be permeable to solutes with larger diameter, such as silicic acid and arsenous acids. However, to date there is no data-mining or direct experimental evidences for the permeability of such larger solutes for dicot NIP2s, although they exhibit similar three-dimensional structures as those in grasses. It is therefore intriguing to investigate the molecular mechanisms that drive the evolution of plant NIP2s.ResultsThe NIP III subgroup is more ancient with a divergence time that predates the monocot-dicot split. The proliferation of NIP2 genes in modern grass species is primarily attributed to whole genome and segmental chromosomal duplication events. The structure of NIP2 genes is relatively conserved, possessing five exons and four introns. All NIP2s possess an ar/R filter consisting of G, S, G, and R, except for the cucumber CsNIP2;2, where a small G in the H2 is substituted with the bulkier C residue. Our maximum likelihood analysis revealed that NIP2s, especially the loop A (LA) region, have undergone strong selective pressure for adaptive evolution. The analysis at the amino acid level provided strong statistical evidences for the functional divergence between monocot and dicot NIP III subgroup proteins. In addition, several SDPs (Specificity Determining Positions) responsible for functional specificity were predicted.ConclusionsThe present study provides the first evidences of functional divergence between dicot and monocot NIP2s, and suggests that positive selection, as well as a radical shift of evolutionary rate at some critical amino acid sites is the primary driver. These findings will expand our understanding to evolutionary mechanisms driving the functional diversification of monocot and dicot NIP III subgroup proteins.

Dataset Information

Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix.

Publications

Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix.

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