The complete mitochondrial genome sequence of the cutlassfish Trichiurus japonicus (Perciformes: Trichiuridae): Genome characterization and phylogenetic considerations
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Abstract
Mitochondrial genome sequence and structure analysis has become a powerful tool for
studying molecular evolution and phylogenetic relationships. To understand the systematic
status of Trichiurus japonicus in suborder Scombroidei, we determined the complete
mitochondrial genome (mitogenome) sequence using the long-polymerase chain reaction
(long-PCR) and shotgun sequencing method. The entire mitogenome is 16,796bp in length
and has three unusual features, including (1) the absence of tRNA(Pro) gene, (2) the
possibly nonfunctional light-strand replication origin (O(L)) showing a shorter loop
in secondary structure and no conserved motif (5'-GCCGG-3'), (3) two sets of the tandem
repeats at the 5' and 3' ends of the control region. The three features seem common
for Trichiurus mitogenomes, as we have confirmed them in other three T. japonicus
individuals and in T. nanhaiensis. Phylogenetic analysis does not support the monophyly
of Trichiuridae, which is against the morphological result. T. japonicus is most closely
related to those species of family Scombridae; they in turn have a sister relationship
with Perciformes members including suborders Acanthuroidei, Caproidei, Notothenioidei,
Zoarcoidei, Trachinoidei, and some species of Labroidei, based on the current dataset
of complete mitogenome. T. japonicus together with T. brevis, T. lepturus and Aphanopus
carbo form a clade distinct from Lepidopus caudatus in terms of the complete Cyt b
sequences. T. japonicus mitogenome, as the first discovered complete mitogenome of
Trichiuridae, should provide important information on both genomics and phylogenetics
of Trichiuridae.