Evidence for mi RNA ‐mediated modulation of the host transcriptome in cnidarian–dinoflagellate symbiosis

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 mi RNA s in the sea anemone Aiptasia , a model system for cnidarian–dinoflagellate endosymbiosis. Aiptasia encodes mainly species‐specific mi RNA s, and there appears to have been recent differentiation within the Aiptasia genome of mi RNA s that are commonly conserved among anthozoan cnidarians. Analysis of mi RNA expression showed that both conserved and species‐specific mi RNA s are differentially expressed in response to endosymbiont infection. Using cross‐linking immunoprecipitation of Argonaute, the central protein of the mi RNA ‐induced silencing complex, we identified mi RNA binding sites on a transcriptome‐wide scale and found that the targets of the mi RNA s regulated in response to symbiosis include genes previously implicated in biological processes related to Symbiodinium infection. Our study shows that cnidarian mi RNA s recognize their mRNA targets via high‐complementarity target binding and suggests that mi RNA ‐mediated modulations of genes and pathways are important during the onset and maintenance of cnidarian–dinoflagellate endosymbiosis.

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