Abstract
miRNAs play important role in the various physiological and evolutionary processes, however, there is no data allowing comparison of evolutionary differences between various ecotypes adapted to different environmental conditions and specimen demonstrating immediate physiological response to the environmental changes. We compared miRNA expression profiles between marine and freshwater stickleback populations of the three-spined stickleback to identify the evolutionary differences. To study the immediate physiological response to foreign environment, we explored the changes induced by transfer of marine sticklebacks into freshwater environment and vice versa. Comparative analysis of changes in miRNA expression suggested that they are driven by three independent factors: (1) non-specific changes in miRNA expression under different environmental conditions; (2) specific response to freshwater conditions in the marine stickleback ecotype; (3) specific response to extreme osmotic conditions for both marine and freshwater ecotypes during the contact with non-native environment. Gene Ontology enrichment analysis of differential expressed miRNA targets supports our current hypothesis.
Highlights
IntroductionMicroRNAs (miRNAs) are small (approximately 22 nucleotides in length) non-coding RNAs involved in post-translational regulation of gene expression
MicroRNAs are small non-coding RNAs involved in post-translational regulation of gene expression
Here we proposed the hypothesis of three separate trends that modulate the miRNA expression: 1) non-specific changes under different environmental conditions; 2) specific response to freshwater conditions in the marine sticklebacks; 3) specific response to extreme osmotic conditions for both ecotypes
Summary
MicroRNAs (miRNAs) are small (approximately 22 nucleotides in length) non-coding RNAs involved in post-translational regulation of gene expression. It was demonstrated that miR-30c is an important regulator of osmotic balance in Nile tilapia (Oreochromis niloticus); loss of function of this miRNA expressed in kidney resulted in disruption of the response to osmotic stress[15] Another member of miR-8 family in Nile tilapia - miR-429 - directly regulates the transcription factor of osmotic regulation 1 (OSTF1), loss of miR-429 functions substantially increases OSTF1 level and leads to changes in the ionic concentration and osmotic stress[16]. Isolation in new freshwater habitats results in the development of freshwater resident population that eventually changes the morphotype and acquires other features that allow surviving in freshwater habitats These features make the three-spined stickleback a useful model for the adaptive evolution studies. There are several studies on genome-wide changes in the process of adaptive speciation in the three-spined stickleback[18,19,20] that identified genomic “islands of divergences” - loci with high concentration of “freshwater” polymorphisms
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