miRNA-target complementarity in cnidarians resembles its counterpart in plants

Area of Science:

• Developmental Biology
• Molecular Biology
• Evolutionary Biology

Background:

• MicroRNAs (miRNAs) are key post-transcriptional regulators controlling gene expression.
• Animal miRNAs typically use a seed sequence for translational repression, while plant miRNAs rely on near-full complementarity for mRNA cleavage.
• Cnidarian miRNAs were recently found to resemble plant miRNAs in their mechanism, but seed-based regulation potential remained unclear.

Purpose of the Study:

• To investigate the complementarity requirements for miRNA activity in the cnidarian Nematostella vectensis.
• To determine if bilaterian-like seed-based miRNA targeting is functional in cnidarians.
• To compare miRNA-target interactions across cnidarians and other metazoans.

Main Methods:

• Experimental manipulation of miRNA-target complementarity in Nematostella vectensis.
• Assessment of miRNA-mediated gene knockdown efficiency based on binding site characteristics.
• Comparative analysis of miRNA silencing mechanisms in Nematostella, Hydractinia, and zebrafish.

Main Results:

• Seed-only or seed and supplementary 3' complementarity, typical of bilaterian miRNAs, was insufficient for effective miRNA-mediated knockdown in Nematostella.
• Mismatches within the miRNA-target cleavage site reduced gene silencing efficiency.
• A typical bilaterian miRNA targeting strategy (three seed sites) was ineffective in zebrafish but functional in Nematostella and Hydractinia.

Conclusions:

• Cnidarian miRNAs exhibit functional similarities to plant miRNAs, emphasizing extensive complementarity for target recognition and cleavage.
• Seed-based regulatory mechanisms, common in bilaterians, are not functional in the studied cnidarians.
• These findings support a potential shared evolutionary origin for miRNA systems in plants and animals.