Involved in the metabolism of all major classes of plastid RNAs. Required for efficient 3'-end processing of mRNAs and 3'-end maturation of rRNA transcripts, but is not sufficient to mediate their degradation. Mediates tRNA degradation. May function as a poly(A) mRNA 3'-5' degrading phosphorylase (By similarity). phosphate + RNA(n+1) = a ribonucleoside 5'-diphosphate + RNA(n) Belongs to the polyribonucleotide nucleotidyltransferase family. Sequencing errors.