Regulatory Roles of Small RNAs in Forest Trees

Noncoding RNA molecules with gene expression regulatory roles have been intensively studied over the last decade across all groups of organisms. The small RNAs, usually ranging between 20 and 24 nucleotides in length, are among major regulators of diverse biological processes in plants, from growth and development to environmental responses. In forest trees, these molecules have also been identified and in some cases shown to play important functions in the control of the characteristic features of these organisms. Despite the difficulties in the investigation of small RNAs in forest trees due to the lack of wide genome resources and the usually challenging experimental characterization, several studies are already available in forest species from the angiosperms and gymnosperms. Such studies will be reviewed here, focusing on the microRNAs associated with embryo/seed development, phase change, flowering, secondary growth, and responses to abiotic stresses and biotic interactions.