Gene expression is regulated at many stages not merely at the level of transcription. Among the important post-transcriptional processes, RNA turnover has a crucial role. The stability of mRNA in the cytosol of eukarya is increased by the addition of a 3' poly(A) extension. By contrast, this process mediates rapid RNA decay in prokarya. How is mRNA turnover regulated in mitochondria? Their monophyletic, alpha-proteobacterial origin predicts that polyadenylation will induce rapid decay by nucleases and associated factors that are similar to their bacterial ancestors. In this article, however, we report that the regulation of mitochondrial mRNA turnover in diverse species is surprisingly different.