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Genetic structure of skipjack tuna Katsuwonus pelamis from the Indian region was investigated using sequence data of mitochondrial DNA (mtDNA) D-loop region. A total of 315 individuals were sampled from six major fishing grounds around the east and west coasts of India including the Andaman (Port Blair) and Lakshadweep (Minicoy) Islands. Nucleotide and gene diversities were high in all the sample collections. Significant genetic heterogeneity was observed for the mtDNA sequence data among sites (φ(ST) = 0·0273, P < 0·001). Analysis of molecular variance (AMOVA) showed significant genetic variation among four groups (φ(CT) = 0·0261, P < 0·05) which was also supported by spatial AMOVA results. The null hypothesis of single panmictic population of K. pelamis along the Indian coast can thus be rejected. Phylogenetic analysis of the mtDNA sequence data showed the presence of four clades of K. pelamis in the Indian waters. There was no clear pattern, however, of haplotypes and geographic location among samples. The results of this study suggest the occurrence of four genetically differentiated groups of K. pelamis across the coastal waters of India.

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In order to assess the DNA sequence variation and phylogenetic relationship among five tuna species (Auxis thazard, Euthynnus affinis, Katsuwonus pelamis, Thunnus tonggol, and T. albacares) out of all four tuna genera, partial sequences of the mitochondrial DNA (mtDNA) D-loop region were analyzed. The estimate of intra-specific sequence variation in studied species was low, ranging from 0.027 to 0.080 [Kimura's two parameter distance (K2P)], whereas values of inter-specific variation ranged from 0.049 to 0.491. The longtail tuna (T. tonggol) and yellowfin tuna (T. albacares) were found to share a close relationship (K2P = 0.049) while skipjack tuna (K. pelamis) was most divergent studied species. Phylogenetic analysis using Maximum-Likelihood (ML) and Neighbor-Joining (NJ) methods supported the monophyletic origin of Thunnus species. Similarly, phylogeny of Auxis and Euthynnus species substantiate the monophyly. However, results showed a distinct origin of K. pelamis from genus Thunnus as well as Auxis and Euthynnus. Thus, the mtDNA D-loop region sequence data supports the polyphyletic origin of tuna species.

Kawakawa Euthynnus affinis is an epipelagic migratory tuna species, widely distributed in the tropical and subtropical waters of the Indo-Pacific region. Kawakawa constitutes the largest tuna fishery in the Indian waters. In the present study, genetic variation was assessed using sequence analyses of Mitochondrial DNA (mtDNA) D-loop region. A 500 bp segment of D-loop region was sequenced in 400 samples collected from eight localities (Veraval (VE), Ratnagiri (RA), Kochi (KO), Kavaratti (KA), Port-Blair (PB), Tuticorin (TU), Pondicherry (PO), and Vizag (VI)) along the Indian coast. Analysis of molecular variance of mtDNA data revealed no significant genetic differentiation among sites the (U ST = 0.0028, P = 0.20723) indicating a single population along the Indian coast. Phylogenetic analysis revealed no obvious phylogeographic pattern separating the eight samples of kawakawa. However, the genealogical relationships demonstrated that mtDNA D-loop sequences belong to two different clades (clade I and clade II). Clade I is the major clade which consists of more than 98 % specimens from each regional population while clade II has individuals from only three populations (VE, PO, and VI). Results of genetic analyses of the present study support a single stock management of kawakawa along the Indian coast.

Frigate tuna Auxis thazard thazard is a cosmopolitan species and one of the smallest members of the tribe Thunnini (the true tunas), and currently managed as a single stock. In the present study, genetic variation was surveyed using sequence data of mitochondrial DNA D-loop region to test for the presence of genetic stock structure of frigate tuna along the Indian coast. A total of 364 individuals were sampled from 8 major fishing zones along the Indian coast. Significant genetic heterogeneity was observed for the sequence data (F ST = 0.0439, P = < 0.001). Analysis of molecular variance (AMOVA) showed significant genetic variation among the three groups analysed (F CT = 0.1223, P = < 0.05), which was also supported by spatial AMOVA results. Therefore, the null hypothesis of single panmictic population of frigate tuna along the Indian coast can be rejected. Phylogenetic analysis of nucleotide sequences demonstrated that frigate tuna can be grouped into three different mitochondrial clades (Clades I, II and III). However, there were no significant genealogical branches or clusters of samples corresponding to sampling locality. The results of the present study suggest the possibility of three genetically differentiated units of frigate tuna across the coastal waters of India.

The population structure and genetic diversity of Rohu (Labeo rohita Hamilton, 1822) was studied by analysis of the partial sequences of mitochondrial DNA cytochrome b region. We examined 133 samples collected from six locations in three geographically isolated rivers of India. Analysis of 11 haplotypes showed low haplotype diversity (0.00150), nucleotide diversity (π) (0.02884) and low heterogeneity value (0.00374). Analysis of molecular variance (AMOVA) revealed the genetic diversity of L. rohita within population is very high than between the populations. The Fst scores (-0.07479 to 0.07022) were the indication of low genetic structure of L. rohita populations of three rivers of India. Conspicuously, Farakka-Bharuch population pair Fst score of 0.0000, although the sampling sites are from different rivers. The phylogenetic reconstruction of unique haplotypes revealed sharing of a single central haplotype (Hap_1) by all the six populations with a point mutations ranging from 1-25 nucleotides.

Laccases belong to multicopper oxidases, a widespread class of enzymes implicated in many oxidative functions in various industrial oxidative processes like production of fine chemicals to bioremediation of contaminated soil and water. In order to understand the mechanisms of substrate binding and interaction between substrates and Pycnoporus cinnabarinus laccase, a homology model was generated. The resulted model was further validated and used for docking studies with toxic industrial dyes- acid blue 74, reactive black 5 and reactive blue 19. Interactions of chemical mediators with the laccase was also examined. The docking analysis showed that the active site always cannot accommodate the dye molecules, due to constricted nature of the active site pocket and steric hindrance of the residues whereas mediators are relatively small and can easily be accommodated into the active site pocket, which, thereafter leads to the productive binding. The binding properties of these compounds along with identification of critical active site residues can be used for further site-directed mutagenesis experiments in order to identify their role in activity and substrate specificity, ultimately leading to improved mutants for degradation of these toxic compounds.