Lesser known relatives of miRNA

Since the discovery of RNAi (RNA interference) major attention has focused on studying miRNA (microRNA) and siRNA (small interfering RNA). However, within the last few years, several other small ncRNAs (non-coding RNAs) have been discovered and thus various newer acronyms representing these 'other' classes of small ncRNAs have populated the literature. Of these, piRNA (Piwi-interacting RNA) has been gaining importance because of its role as the guardian of the germline genome. Some of the other newly discovered small ncRNAs have been mostly reported in plants, and they are yet to be studied more comprehensively. Nevertheless, piRNA and the 'other' small ncRNAs deserve some discussion because they are members of the increasingly large family of small ncRNAs. (C) Published by Elsevier Inc.