The Meaning of the Microprocessor: Accounting for Evolution of Structural-Functional Novelty in the Canonical microRNA Biogenesis Pathway

Subsidiary to detection and assignment of novel microRNAs in non-model taxa, it is standard to identify and compare genomic or transcript sequence of Drosha and Pasha. Detection of both (1) bona fide microRNAs and (2) presence of Drosha/Pasha orthologs is often assumed to represent a functional canonical eumetazoan microRNA biogenesis pathway. However, this is not often experimentally confirmed in non-model taxa, and therefore the assumption is not necessarily valid. Below I describe several lines of evidence for this assertion.