Cnidarian microRNAs frequently regulate targets by cleavage

Area of Science:

• Evolutionary biology
• Molecular biology
• Genomics

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression in bilaterians, primarily through translational inhibition and mRNA destabilization.
• Plant miRNAs commonly induce target mRNA cleavage due to high complementarity.
• The function and evolution of miRNAs in nonbilaterian animals, like Cnidaria, remain largely unexplored.

Purpose of the Study:

• To investigate the repertoire and biological activity of miRNAs in the sea anemone Nematostella vectensis, a cnidarian model organism.
• To compare miRNA-mediated gene regulation in Cnidaria with that in Bilateria and plants.

Main Methods:

• Bioinformatic analysis to identify novel miRNAs in Nematostella vectensis.
• Experimental validation of miRNA targets and their modes of action.
• Comparative analysis of miRNA repertoires and target site conservation across related species.

Main Results:

• Discovery of numerous novel miRNAs in Nematostella, expanding the known miRNA gene count to 87.
• Demonstration that Nematostella miRNAs frequently induce target mRNA cleavage, similar to plant miRNAs and siRNAs.
• Observation of common coexpression of miRNAs with their targets in Nematostella, contrasting with bilaterian systems.
• Evidence of conserved miRNA-directed cleavage in other cnidarians, including Hydra.

Conclusions:

• MicroRNA gene turnover in Cnidaria appears significantly higher than in other metazoan groups.
• The predominant mode of miRNA action in Cnidaria involves target mRNA cleavage, suggesting an ancestral regulatory mechanism.
• Post-transcriptional regulation by miRNAs likely operates differently in Cnidaria compared to Bilateria.