Abstract
Reef-building corals and other cnidarians living in symbiotic relationships with intracellular, photosynthetic dinoflagellates in the genus Symbiodinium undergo transcriptomic changes during infection with the algae and maintenance of the endosymbiont population. However, the precise regulatory mechanisms modulating the host transcriptome are unknown. Here, we report apparent post-transcriptional gene regulation by miRNAs in the sea anemone Aiptasia, a model system for cnidarian-dinoflagellate endosymbiosis. Aiptasia encodes mainly species-specific miRNAs, and there appears to have been recent differentiation within the Aiptasia genome of miRNAs that are commonly conserved among anthozoan cnidarians. Analysis of miRNA expression showed that both conserved and species-specific miRNAs are differentially expressed in response to endosymbiont infection. Using cross-linking immunoprecipitation of Argonaute, the central protein of the miRNA-induced silencing complex, we identified miRNA binding sites on a transcriptome-wide scale and found that the targets of the miRNAs regulated in response to symbiosis include genes previously implicated in biological processes related to Symbiodinium infection. Our study shows that cnidarian miRNAs recognize their mRNA targets via high-complementarity target binding and suggests that miRNA-mediated modulations of genes and pathways are important during the onset and maintenance of cnidarian-dinoflagellate endosymbiosis.
Highlights
The trophic and structural basis of one of the most important marine ecosystems, coral reefs, relies on a functional endosymbiosis between cnidarian coral hosts and photosynthetic dinoflagellate symbionts in the genus Symbiodinium, which reside within vesicles in the host’s gastrodermal cells (Davy, Allemand & Weis, 2012)
Using cross-linking immunoprecipitation of Argonaute, the central protein of the miRNA-induced silencing complex, we identified miRNA binding sites on a transcriptome-wide scale and found that the targets of the miRNAs regulated in response to symbiosis include genes previously implicated in biological processes related to Symbiodinium infection
We investigated the Aiptasia miRNA repertoire using replicate small-RNA libraries prepared from Aiptasia polyps at different stages of infection with the endosymbiotic S. minutum strain SSB01
Summary
The trophic and structural basis of one of the most important marine ecosystems, coral reefs, relies on a functional endosymbiosis between cnidarian coral hosts and photosynthetic dinoflagellate symbionts in the genus Symbiodinium, which reside within vesicles (symbiosomes) in the host’s gastrodermal cells (Davy, Allemand & Weis, 2012). In this mutualistic relationship, the host offers a sheltered environment to the alga and provides the inorganic nutrients needed for photosynthesis and growth, whereas the symbiont transfers the majority of its photosynthetic products to the host (Muscatine & Porter, 1977). Little is yet known about the higher-level regulatory mechanisms that might participate in the modulation and orchestration of such changes in gene expression
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