No abstract

The walking catfish Clarias magur (Hamilton, 1822) (magur) is an important catfish species inhabiting the Indian subcontinent. It is considered as a highly nutritious food fish and has the capability to walk to some distance, and survive a considerable period without water. Assembly, scaffolding and several rounds of iterations resulted in 3484 scaffolds covering ∼94% of estimated genome with 9.88 Mb largest scaffold, and N50 1.31 Mb. The genome possessed 23748 predicted protein encoding genes with annotation of 19,279 orthologous genes. A total of 166 orthologous groups represented by 222 genes were found to be unique for this species. The Computational Analysis of gene Family Evolution (CAFÉ) analysis revealed expansion of 207 gene families and 100 gene families have rapidly evolved. Genes specific to important environmental and terrestrial adaptation, viz. urea cycle, vision, locomotion, olfactory and vomeronasal receptors, immune system, anti-microbial properties, mucus, thermoregulation, osmoregulation, air-breathing, and detoxification etc. were identified and critically analyzed. The analysis clearly indicated that C. magur genome possessed several unique and duplicate genes similar to that of terrestrial or amphibians’ counterparts in comparison to other teleostean species. The genome information will be useful in conservation genetics, not only for this species but also be very helpful in such studies in other catfishes.

Whole genome sequencing (WGS) using next generation sequencing technologies paves the way to sequence the mitochondrial genomes with greater ease and lesser time. Here, we used the WGS data of Clarias batrachus, generated from Roche 454 and Ion Torrent sequencing platforms, to assemble the complete mitogenome using both de novo and reference based approaches. Both the methods yielded almost similar results and the best assembled mitogenome was of 16,510 bp size (GenBank Acc. No. KM259918). The mitogenome annotation resulted in 13 coding genes, 22 tRNA genes, 2 rRNA genes and one control region, and the gene order was found to be identical with other catfishes. Variation analyses between assembled and the reference (GenBank Acc. No. NC_023923) mitogenome revealed 51 variations. The phylogenetic analysis of coding DNA sequences and tRNA supports the monophyly of catfishes. Two SSRs were identified in C. batrachus mitogenome, out of which one was unique to this species. Based on the relative rate of gene evolution, protein coding mitochondrial genes were found to evolve at a much faster pace than the d-loop, which in turn are followed by the rRNAs; the tRNAs showed wide variability in the rate of sequence evolution, and on average evolve the slowest. Among the coding genes, ND2 evolves most rapidly. The variations present in the coding regions of the mitogenome and their comparative analyses with other catfish species may be useful in species conservation and management programs.

The complete mitogenome of Himalayan black bear (Ursus thibetanus laniger) from Indian Himalayan region was assembled following the modified approach of mitochondrial baiting and mapping using the next-generation sequencing reads. The complete mitogenome was of 16,556 bp long, consisted of 37 genes that contained 13 protein-coding genes, 22 tRNAs, 2 rRNAs and 1 control region. The complete base composition was 31.33% A, 15.24% G, 25.45%C, and 27.98%T and gene arrangement was similar to the other sub-species of Asiatic black bear. The relative synonymous codon usage analysis revealed the maximum abundance of Isoleucine, Tyrosine, Leucine and Threonine. The assembled mitogenome of U. t. laniger exhibited 99% similarity with the mitogenomes of Himalayan black bear available from Nepal and Tibetan Plateau-Himalaya region. The findings of the present study has proven low depth sequencing data, adequate and highly efficient in rapid recovering the mitochondrial genome by overcoming the conventional strategies of obtaining long-range PCR and subsequently drawing phylogenetic inferences.

(2017) Rapid recovery of complete mitogenome of Indian major carp, Catla catla from low depth paired end Illumina sequencing, Mitochondrial DNA Part B, 2:1, 155-156,