The genetic relationships among eight species and three varieties within the genus Larix were studied by analysing restriction fragment length polymorphism in chloroplast DNA (cpDNA). Six restriction enzymes and 11 predominantly nonoverlapping probes from Pinuscontorta Dougl. ex Loud, were employed. No variation in cpDNA was detected within taxa, and mean levels of nucleotide divergence (d) among species were low. Six taxa were not resolved by the analysis, and the maximum d value recorded was 0.0096. Genetic distance data and neighbor joining were used to construct a tree of genetic relatedness among taxa, which resolved three groups. Larixgriffithiana Carr. was genetically distinct from all other taxa. A second group comprised Larixsibirica Ledeb. from Eurasia and two North American species, Larixlaricina (Du Roi) K Koch, and Larixoccidentalis (Nutt.). The third group consisted of the Chinese and Japanese taxa Larixgmelinii (Rupr.) Rupr. ex Kuzen., Larixpotaninii Batal., and Larixkaempferi (Lamb.) Carr. together with European larch, Larixdecidua Mill. These groupings do not correspond to traditional patterns of classification within the genus, which are based primarily on features of the female cone. The results from the cpDNA analysis are interpreted in the context of other information about the evolutionary history of the genus.
Mitochondria are important organelles with independent genetic material of eukaryotic organisms. In this study, we sequenced and analyzed the complete mitogenome of a small cyprinid fish, Microphysogobio elongatus (Yao & Yang, 1977). The mitogenome of M. elongatus is a typical circular molecule of 16,612 bp in length containing 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and a 930 bp control region. The base composition of the M. elongatus mitogenome is 30.8% A, 26.1% T, 16.7% G, and 26.4% C. All PCGs used the standard ATG start codon with the exception of COI. Six PCGs terminate with complete stop codons, whereas seven PCGs (ND2, COII, ATPase 6, COIII, ND3, ND4, and Cyt b) terminate with incomplete (T or TA) stop codons. All tRNA genes exhibited typical cloverleaf secondary structures with the exception of tRNASer(AGY), for which the dihydrouridine arm forms a simple loop. The phylogenetic analysis divided the subfamily Gobioninae in three clades with relatively robust support, and that Microphysogobio is not a monophyletic group. The complete mitogenome of M. elongatus provides a valuable resource for future studies about molecular phylogeny and/or population genetics of Microphysogobio.
The mitochondrial genome (mitogenome) has been widely used as a molecular marker to investigate phylogenetic analysis and evolutionary history in fish. However, the study of mitogenomes is still scarce in the family Bagridae. In this study, the mitogenomes of Tachysurus brachyrhabdion and T. gracilis were sequenced, annotated, and analyzed. The mitogenomes were found to be 16,532 bp and 16,533 bp, respectively, and each contained 37 typical mitochondrial genes, which are 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and a control region. All PCGs begin with the codon ATG, except for the cytochrome c oxidase subunit 1 (COI) gene, while seven PCGs end with an incomplete termination codon. All tRNA genes can fold into their typical cloverleaf secondary structures, except for tRNASer(AGY), which lacks the dihydrouracil arm. The Ka/Ks ratios for all PCGs are far lower than one. Phylogenetic analyses based on Bayesian inference (BI) and maximum likelihood (ML) showed that the two clades in Bagridae excluded Rita rita. The monophyly of Tachysurus supports previous research and the traditional classification that Leiocassis, Pseudobagrus, Pelteobagrus, and Tachysurus belong to one genus (Tachysurus). These findings provide a phylogenetic basis for future phylogenetic and taxonomic studies of Bagridae.
Nowadays, the global fish consumption continues to rise along with the continuous growth of the population, which has led to the dilemma of overfishing of fishery resources. Especially high-value fish that are overfished are often replaced by other fish. Therefore, the accurate identification of fish products in the market is a problem worthy of attention. In this study, full-DNA barcoding (FDB) and mini-DNA barcoding (MDB) used to detect the fraud of fish products in Guiyang, Guizhou province in China. The molecular identification results showed that 39 of the 191 samples were not consistent with the labels. The mislabelling of fish products for fresh, frozen, cooked and canned were 11.70%, 20.00%, 34.09% and 50.00%, respectively. The average kimura 2 parameter distances of MDB within species and genera were 0.27% and 5.41%, respectively; while average distances of FDB were 0.17% within species and 6.17% within genera. In this study, commercial fraud is noticeable, most of the high-priced fish were replaced of low-priced fish with a similar feature. Our study indicated that DNA barcoding is a valid tool for the identification of fish products and that it allows an idea of conservation and monitoring efforts, while confirming the MDB as a reliable tool for fish products.
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