Non Coding RNAs in Plants

Abstract

Small RNAs have emerged as important regulators of gene expression in eukaryotic organisms. Plant small RNAs are cleaved from longer fully or partially double-stranded RNA by Dicer. In most small RNA pathways, populations of overlapping small RNAs are produced. However, in some pathways double-stranded RNA molecules having unique start sites for cleavage are generated, and processive cleavage of these double-stranded RNAs generates a population of non-overlapping, phased small RNAs. Rice contains at least 40-fold more phased small RNA-generating loci than Arabidopsis, and mutations in genes involved in the biogenesis of phased small RNAs have much more severe phenotypes in rice and maize than in Arabidopsis. These considerations suggest that pathways producing phased small RNAs play a more important role in monocots than in Arabidopsis. To put this new development in context here we review the biogenesis and functions of phased small RNAs in rice.