MiRNAs as promising phylogenetic markers for inferring deep metazoan phylogeny and in support of Olfactores hypothesis

The Long Branch attraction (LBA) artefact induced by fast evolving Urochordata had hindered the interpretation of relationships among 3 subphyla of Chordata. Although Olfactores hypothesis which placed Urochordata rather than Cephalochordata as the closest relatives to Craniata was gradually accepted, every step of phylogenetic reconstruction had to be treated prudential to minimize LBA phenomenon. MiRNAs (microRNAs) are well known for their 1) adherence to organism development, 2) high conservation, and 3) rarity of secondary loss, parallel evolution, and convergence among metazoan. Therefore we suppose miRNAs to be promising candidates to dispel LBA phenomenon. We performed a phylogenetic study upon 35 pre-miRNA datasets and reconstruct Chordata phylogeny which supported Olfactores hypothesis in a more toilless way by applying fewer datasets and unspecified substitution model. This is the first attempt to apply miRNA sequences in interpreting Chordata phylogeny, and we reckon miRNAs as promising phylogenetic markers for illuminating deuterostome evolution.