The biosynthetic pathways and biological scopes of plant small RNAs

RNA silencing plays a crucial role in coordinating the expression, stability, protection and inheritance of eukaryotic genomes. It comprises several mechanisms that invariably depend on core small RNA molecules (sRNAs) and that achieve dedicated sequence-specific functions. Biogenesis and function of sRNAs generally follow a framework that involves main protein families conserved among eukaryotes. The most recent studies have provided structural insights into the function of RNA silencing components, identified novel players of these pathways and highlighted possible emerging classes of sRNA regulators. In this review, we integrate these studies to provide updated views on the biosynthetic pathways and dedicated functions of the endogenous sRNA classes of plants, emphasizing their specialized scopes.