Abstract
BackgroundThe nematode Caenorhabditis elegans is able to take up external double-stranded RNAs (dsRNAs) and mount an RNA interference response, leading to the inactivation of specific gene expression. The uptake of ingested dsRNAs into intestinal cells has been shown to require the SID-2 transmembrane protein in C. elegans. By contrast, C. briggsae was shown to be naturally insensitive to ingested dsRNAs, yet could be rendered sensitive by transgenesis with the C. elegans sid-2 gene. Here we aimed to elucidate the evolution of the susceptibility to external RNAi in the Caenorhabditis genus.Principal FindingsWe study the sensitivity of many new species of Caenorhabditis to ingested dsRNAs matching a conserved actin gene sequence from the nematode Oscheius tipulae. We find ample variation in the Caenorhabditis genus in the ability to mount an RNAi response. We map this sensitivity onto a phylogenetic tree, and show that sensitivity or insensitivity have evolved convergently several times. We uncover several evolutionary losses in sensitivity, which may have occurred through distinct mechanisms. We could render C. remanei and C. briggsae sensitive to ingested dsRNAs by transgenesis of the Cel-sid-2 gene. We thus provide tools for RNA interference studies in these species. We also show that transgenesis by injection is possible in many Caenorhabditis species.ConclusionsThe ability of animals to take up dsRNAs or to respond to them by gene inactivation is under rapid evolution in the Caenorhabditis genus. This study provides a framework and tools to use RNA interference and transgenesis in various Caenorhabditis species for further comparative and evolutionary studies.
Highlights
RNA interference is the inactivation of gene expression induced by double-stranded RNAs [1]
The ability of animals to take up double-stranded RNAs (dsRNAs) or to respond to them by gene inactivation is under rapid evolution in the Caenorhabditis genus
This study provides a framework and tools to use RNA interference and transgenesis in various Caenorhabditis species for further comparative and evolutionary studies
Summary
RNA interference is the inactivation of gene expression induced by double-stranded RNAs (dsRNAs) [1]. The molecular mechanism by which dsRNAs introduced into a cell induce degradation of the corresponding mRNA has been well documented in the nematode Caenorhabditis elegans. In this species, dsRNAs do not need to be injected, but are able to enter cells when the animal is either soaked in a dsRNA preparation [2], or is fed E. coli bacteria that express dsRNAs from a plasmid [3]. The nematode Caenorhabditis elegans is able to take up external double-stranded RNAs (dsRNAs) and mount an RNA interference response, leading to the inactivation of specific gene expression. The uptake of ingested dsRNAs into intestinal cells has been shown to require the SID-2 transmembrane protein in C. elegans. We aimed to elucidate the evolution of the susceptibility to external RNAi in the Caenorhabditis genus
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