Non-protein-coding RNAs, a diverse class of gene regulators, and their action in plants

In recent years, non-protein-coding RNAs (or npcRNAs) have emerged as a major part of the eukaryotic transcriptome. Apart from the well-known housekeeping npcRNAs like rRNAs, tRNAs, snoRNAs and snRNAs, many new regulatory npcRNAs or riboregulators have been discovered and characterized due to the advent of new genomic approaches. This growing number suggests that npcRNAs could play a more important role than previously believed and significantly contribute to the generation of evolutionary complexity in multicellular organisms. Regulatory npcRNAs range from small RNAs (si/miRNAs) to very large transcripts (or long npcRNAs) and play diverse functions in development and/or responses to external stimuli. These riboregulators may affect transcription o translation of other genes and exert their functions through association to ribonucleoprotein particles. In the last years, diverse mechanisms of action and biogenesis of si/miRNAs have been explored in plants but much less is known about the action of long npcRNAs. As plants show a remarkable developmental plasticity to adapt their growth to changing environmental condition, understanding how npcRNAs work may reveal novel mechanisms involved in growth control and differentiation and help to design new tools for biotechnological applications.