An RNA-based approach to sequence the mitogenome of Hypoptopoma incognitum (Siluriformes: Loricariidae)

Comparative analysis of the mitogenomes of two Corydoras (Siluriformes, Loricarioidei) with nine known Corydoras, and a phylogenetic analysis of Loricarioidei

Corydoras is a speciose catfish genus from South America with widely investigated phylogenetic and evolutionary relationships. The complete mitogenomes of C. aeneus and C. paleatus were sequenced, assembled, and annotated using next-generation sequencing. The genome arrangements, gene contents, genome structures, base compositions, evolutionary features, codon usage, and tRNA structures of the two mitogenomes were compared and analyzed with nine published mitogenomes of Corydoras. Phylogenetic analysis was performed using concatenated nucleotide sequences with 13 protein-coding genes and two rRNAs with 44 mitogenomes of Siluriformes. These results provide information on the mitogenomes of eleven Corydoras species and evolutionary relationships within the suborder Loricarioidei, which may be applicable for further phylogenetic and taxonomic studies on Siluriformes and Loricarioidei.

Reducing the information gap on Loricarioidei (Siluriformes) mitochondrial genomics

Background

The genetic diversity of Neotropical fish fauna is underrepresented in public databases. This distortion is evident for the order Siluriformes, in which the suborders Siluroidei and Loricarioidei share equivalent proportion of species, although far less is known about the genetics of the latter clade, endemic to the Neotropical Region. Recently, this information gap was evident in a study about the structural diversity of fish mitochondrial genomes, and hampered a precise chronological resolution of Siluriformes. It has also prevented molecular ecology investigations about these catfishes, their interactions with the environment, responses to anthropogenic changes and potential uses.

Results

Using high-throughput sequencing, we provide the nearly complete mitochondrial genomes for 26 Loricariidae and one Callichthyidae species. Structural features were highly conserved. A notable exception was identified in the monophyletic clade comprising species of the Hemiancistrus, Hypostomini and Peckoltia-clades, a ~60 nucleotide-long deletion encompassing the seven nucleotides at the 3′ end of the Conserved Sequence Block (CSB) D of the control region. The expression of mitochondrial genes followed the usual punctuation pattern. Heteroplasmic sites were identified in most species. The retrieved phylogeny strongly corroborates the currently accepted tree, although bringing to debate the relationship between Schizolecis guntheri and Pareiorhaphis garbei, and highlighting the low genetic variability within the Peckoltia-clade, an eco-morphologically diverse and taxonomically problematic group.

Conclusions

Herein we have launched the use of high-throughput mitochondrial genomics in the studies of the Loricarioidei species. The new genomic resources reduce the information gap on the molecular diversity of Neotropical fish fauna, impacting the capacity to investigate a variety of aspects of the molecular ecology and evolution of these fishes. Additionally, the species showing the partial CSB-D are candidate models to study the replication and transcription of vertebrate mitochondrial genome.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3709-3) contains supplementary material, which is available to authorized users.

The liver transcriptome of suckermouth armoured catfish (Pterygoplichthys anisitsi, Loricariidae): Identification of expansions in defensome gene families

Pterygoplichthys is a genus of related suckermouth armoured catfishes native to South America, which have invaded tropical and subtropical regions worldwide. Physiological features, including an augmented resistance to organic xenobiotics, may have aided their settlement in foreign habitats. The liver transcriptome of Pterygoplichthys anisitsi was sequenced and used to characterize the diversity of mRNAs potentially involved in the responses to natural and anthropogenic chemicals. In total, 66,642 transcripts were assembled. Among the identified defensome genes, cytochromes P450 (CYP) were the most abundant, followed by sulfotransferases (SULT), nuclear receptors (NR) and ATP binding cassette transporters (ABC). A novel expansion in the CYP2Y subfamily was identified, as well as an independent expansion of the CYP2AAs. Two expansions were also observed among SULT1. Thirty-two transcripts were classified into twelve subfamilies of NR, while 21 encoded ABC transporters. The diversity of defensome transcripts sequenced herein could contribute to this species' resistance to organic xenobiotics.