Polyadenylation in RNA Degradation Processes in Plants
Although polyadenylation is best known for stabilizing eukaryotic mRNAs and promoting their translation, the primordial role of polyadenylation is to target RNAs for degradation by 3' 5' exoribonucleases. This ancient mechanism is conserved among bacteria and eukaryotes, and in plants, polyadenylation assisted RNA degradation operates in the nucleus, the chloroplast, and the mitochondrion. Polyadenylation assisted RNA degradation contributes to maturation, turnover, and quality control of a variety of transcripts, the nature of which varies in the different genetic compartments of the plant cell. Moreover, polyadenylation assisted RNA degradation rapidly removes a large variety of novel transcripts of unknown function that are produced by extensive transcription of extragenic regions, in particular from nuclear and mitochondrial genomes. In this chapter, we review the current knowledge of polyadenylation assisted RNA degradation in plants, highlighting the different impact of this RNA degradation pathway on the expression of nuclear, plastidial, or mitochondrial genomes.