Insights into the role of differential gene expression on the ecological adaptation of the snail Littorina saxatilis

Abstract

BackgroundIn the past 40 years, there has been increasing acceptance that variation in levels of gene expression represents a major source of evolutionary novelty. Gene expression divergence is therefore likely to be involved in the emergence of incipient species, namely, in a context of adaptive radiation. In this study, a genome-wide expression profiling approach (cDNA-AFLP), validated by quantitative real-time polymerase chain reaction (qPCR) were used to get insights into the role of differential gene expression on the ecological adaptation of the marine snail Littorina saxatilis. This gastropod displays two sympatric ecotypes (RB and SU) which are becoming one of the best studied systems for ecological speciation.ResultsAmong the 99 transcripts shared between ecotypes, 12.12% showed significant differential expression. At least 4% of these transcripts still displayed significant differences after correction for multiple tests, highlighting that gene expression can differ considerably between subpopulations adapted to alternative habitats in the face of gene flow. One of the transcripts identified was Cytochrome c Oxidase subunit I (COI). In addition, 6 possible reference genes were validated to normalize and confirm this result using qPCR. α-Tubulin and histone H3.3 showed the more stable expression levels, being therefore chosen as the best option for normalization. The qPCR analysis confirmed a higher COI expression in SU individuals.ConclusionsAt least 4% of the transcriptome studied is being differentially expressed between ecotypes living in alternative habitats, even when gene flow is still substantial between ecotypes. We could identify a candidate transcript of such ecotype differentiation: Cytochrome c Oxidase Subunit I (COI), a mitochondrial gene involved in energy metabolism. Quantitative PCR was used to confirm the differences found in COI and its over-expression in the SU ecotype. Interestingly, COI is involved in the oxidative phosphorylation, suggesting an enhanced mitochondrial gene expression (or increased number of mitochondria) to improve energy supply in the ecotype subjected to the strongest wave action.

Contrasting patterns of population connectivity between regions in a commercially important mollusc Haliotis rubra: integrating population genetics, genomics and marine LiDAR data

“…Estimates of neutral genetic diversity in this study indicate a lack of genetic structure at the various hierarchical spatial scales, although adaptive genetic diversity could still be playing a role in the recruitment process. Recent genomic studies of marine fish and molluscs have demonstrated that under strong selection pressures, adaptive variation can be maintained in marine environments despite high levels of gene flow (Galindo et al 2009;Martinez-Fernandez et al 2010;Hess et al 2013;Solas et al 2013;Milano et al 2014). Consequently, patterns of abalone larval settlement and establishment could be determined by underlying adaptive genetic variation, where recruitment at the reef scale is dependent on the settlement of compatible adaptive genotypes.…”

Local and regional scale habitat heterogeneity contribute to genetic adaptation in a commercially important marine mollusc (Haliotis rubra) from southeastern Australia

“…Additionally, adaptive genetic divergences among populations, particularly on finer spatial scales, can assist in deciphering the influence of natural selection on recruitment processes (Marshall, Monro, Bode, Keough, & Swearer, ). Studies on marine fish and invertebrates have demonstrated that adaptive variation can be maintained despite high levels of gene flow (Galindo et al, ; Hess et al, ; Martinez‐Fernandez, Bernatchez, Rolan‐Alvarez, & Quesada, ; Milano et al, ; Sandoval‐Castillo, Robinson, Hart, Strain, & Beheregaray, ; Solas, Sepulveda, & Brante, ), suggesting that selection can influence recruitment processes as some potential recruits are expected to be maladapted to certain habitat types (Marshall et al, ). Information on gene flow and population connectivity informs whether populations can replenish naturally following disturbance and depletion, and when management intervention is required (Whiterod, Zukowski, Asmus, Gilligan, & Miller, ).…”

Among‐lake reciprocal transplants induce convergent expression of immune genes in threespine stickleback

“…Immune gene expression is a commonly used measure of immune traits. Immune gene expression is known to differ among host populations (Jeukens et al 2009;Lenz et al 2013;Martinez-Fernandez et al 2010;McCairns & Bernatchez 2010;Morris et al 2014). Immune gene expression influences host resistance to parasite infection in a variety of ways.…”