Catalytic component of the RNA exosome complex which has 3'->5' exoribonuclease activity and participates in a multitude of cellular RNA processing and degradation events. Required for 5.8S rRNA intermediate processing and the degradation of 5' external transcribed spacer (5' ETS), a maturation by-product of rRNA synthesis. Is not involved in the degradation of turnip crinkle virus (TCV) RNA and significant virus resistance (PubMed:24244451). Required for normal development of female gametophytes and early embryogenesis (PubMed:20798041, PubMed:24244451). Probable component of the RNA exosome complex. A number of isoforms are produced. According to EST sequences. Aborted development of female gametophytes. Belongs to the RNR ribonuclease family.