Hypervariability of ascidian mitochondrial gene order: Exposing the Myth of deuterostome organelle genome stability

Carmela Gissi, Graziano Pesole, Francesco Mastrototaro, Fabio Iannelli, Vanessa Guida, Francesca Griggio

Research output: Contribution to journalArticlepeer-review


The few sequenced mitochondrial (mt) genomes of the class Ascidiacea (Chordata, Tunicata), mostly belonging to congeneric species of the Phlebobranchia order, show extraordinary gene order rearrangements. In order to assess if this hypervariability in gene order is a general feature of Ascidiacea, we report here the gene arrangement of five ascidians belonging to the Aplousobranchia and Stolidobranchia orders. Our data show that Ascidiacea are characterized by: 1) extensive gene order rearrangements both within and between the three major lineages; 2) lack of significant similarities to the gene order of other deuterostomes; and 3) an extent of rearrangements comparable with that of Mollusca (especially the Gastropoda, Bivalvia, and Scaphopoda classes), a phylum with highly rearranged mtDNAs. The only conserved feature is the location of all genes on the same strand, which suggests that selective constraints are related to the mt transcription. Finally, a higher mobility of the tRNA genes is undetectable because of saturation effect, and only the partially conserved cox2-cob gene block seems to retain some phylogenetic signals.

Original languageEnglish
Pages (from-to)211-215
Number of pages5
JournalMolecular Biology and Evolution
Issue number2
Publication statusPublished - Feb 2010


  • Ascidians
  • Gene order
  • Mitochondrial genome
  • Rearrangements

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Ecology, Evolution, Behavior and Systematics


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