Hu Shu

The complete mitochondrial genome of the Zig-zag eel Mastacembelus armatus (Teleostei, Mastacembelidae).

Abstract In this paper, the complete mitochondrial DNA (mtDNA) sequence of Mastacembelus armatus was determined. The mitochondrial genome is 16,486 bp in length, including 13 protein-coding genes, 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs) and a noncoding control region as those found in other vertebrates, with the gene identical to that of typical vertebrates. The overall base composition of the heavy strand are 25.28% of A, 29.13% of T, 14.65% of C and 30.93% of G, with a slight AT bias of 54.41%. With the exception of ND6 and eight tRNA genes, all other mitochondrial genes are encoded on the heavy strand.

Masculinization and reproductive effects in western mosquitofish (Gambusia affinis) after long-term exposure to androstenedione

Androstenedione (AED) is a naturally occurring steroid hormone. It is metabolized to potent androgens, which may induce androgenic effects in fish. However, little is known whether and how the androgens interfere with the fish gonadal development and reproduction. This study aimed at demonstrating the effects of long-term AED exposure on reproduction and development in mosquitofish (Gambusia affinis). The growth, development and several morphological endpoints, including the segment number and length of anal fin, histological changes of gonads and liver, were evaluated in mosquitofish during development from fertilized embryo to adulthood (180 days) after exposure of AED at environmentally relevant concentrations. We found that the growth (length, body weight and condition factor) of fish was negatively correlated with AED concentration in females, but not in males. The significant elongation of the ray and increment of segment numbers in the anal fin, were detected in all mosquitofish after exposure. Moreover, AED exposure (0.4gµ/L) caused damages in gonads and reduced the number of pregnant females. These findings indicate that AED has adverse effects on the growth and development of the western mosquitofish after long-term exposure (180d). Long-term exposure (180d) to AED, including environmentally relevant concentration (0.4µg/L and 4µg/L), induced masculinization in female mosquitofish under the experimental conditions.

The complete mitochondrial genome of the Megalobrama skolkovii (Cyprinidae: Cultrinae).

Abstract The complete mitochondrial DNA (mtDNA) sequence of Megalobrama skolkovii was first presented in this study. The mitochondrial genome is 16,620 bp in length, including 13 protein-coding genes, 2 ribosomal RNA gens (12S rRNA and 16S rRNA), 22 transfer RNA genes (tRNA) and a control region (D-loop), with the gene identical to that of typical vertebrates. The overall base composition of the light strand are 31.23% A, 24.73% T, 16.16% G and 27.88% C. Two copies of tandem repeat sequence was found in the control region.

The complete mitochondrial genome of the Gray's grenadier anchovy Coilia grayii (Teleostei, Engraulidae)

Abstract In this paper, the complete mitochondrial DNA (mtDNA) sequence of Coilia grayii was determined. The mitochondrial genome was 16,851 bp in length, including 13 protein-coding genes, 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs) and a non-coding control region as those found in other vertebrates, with the gene identical to that of typical vertebrates. The overall base composition of the heavy strand were 26.09% of A, 31.14% of T, 15.58% of C and 27.19% of G, with a slight AT bias of 57.23%. With the exception of ND6 and eight tRNA genes, all other mitochondrial genes were encoded on the heavy strand.

Association between expression levels and growth trait-related SNPs located in promoters of the MC4R and MSTN genes in Spinibarbus hollandi

Melanocortin 4 receptor: (MC4R) and Myostatin (MSTN) are two important growth trait-related genes in animals. In this study, we showed that two SNPs, MC4R-719A>G and MSTN-519C>T, found in the promoters of the MC4R and MSTN genes, respectively, are both associated with growth traits in Spinibarbus hollandi. Furthermore, we observed that there were significant associations between the expression levels of the MC4R and MSTN genes and these two growth trait-related SNPs. The expression level of MC4R gene in brain was lower in GG genotype fish with extremely high growth performance than that in AA genotype fish with extremely low growth performance. Expression level of the MSTN gene in muscle was lower in TT genotype fish with extremely high growth performance than that in CC and CT genotype fish with lower growth performance. The results indicated that these SNPs located in the promoters of MC4R and MSTN are associated with growth-related traits through modification of gene expression levels. The MSTN and MC4R SNPs may have useful application in effective marker-assisted selection aimed to increase output in S. hollandi.

Modulation of transcription of genes related to the hypothalamic–pituitary–gonadal and the hypothalamic–pituitary–adrenal axes in zebrafish (Danio rerio) embryos/larvae by androstenedione

This study aimed to determine the effects of Androstenodione (AED) on the transcriptional expression of genes involved in the hypothalamic-pituitary-gonadal (HPG) and the hypothalamic-pituitary-adrenal (HPA) axes in the zebrafish embryos/larvae. Zebrafish embryos were exposed to 0, 4.0, 45.0, 487.0, and 980.0 ng/L of AED from the day of fertilization to 144 h post fertilization (hpf), during which the transcriptional profiles of key genes related to the HPG and HPA axes were examined daily using quantitative real-time PCR. The AED exposure significantly up-regulated several receptor signaling pathways and the key genes involved in various steps of the steroidogenic pathways were also affected. In addition, the AED exposure could significantly modulate the transcriptional profiles of the other target genes related to hypothalamic and pituitary hormones. The findings of this study suggest that AED, at environmentally relevant concentrations, affects the adrenal endocrine systems and the reproduction of zebrafish by interrupting the HPG and HPA axes.

The complete mitochondrial genome of the duskytail grouper Epinephelus bleekeri (Serranidae: Epinephelinae).

Abstract The complete mitochondrial genome of Epinephelus bleekeri was first presented in this study. It is 17,227 bp in length, consisted of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a non-coding control region. The overall base composition of the H-strand is 26.32% A, 28.65% T, 28.72% G and 16.31% C. With the exception of ND6 and eight tRNA genes, all other mitochondrial genes are encoded on the heavy strand. In particular, gene duplication is found on the tRNA-Asp gene, and five tandem repeat of this gene in E. bleekeri is different from most other vertebrates. The control region is rich in A + T (67.12%) and poor in G (14.00%), and tandem repeat sequences are observed in this non-coding region, indicating a useful marker for population genetic studies.

Identification and functional characterization of two Secretogranin II genes in orange-spotted grouper (Epinephelus coioides)

Secretoneurin (SN) is an important stimulator of pituitary luteinizing hormone (LH) synthesis and secretion in goldfish. It is unknown whether this neuropeptide performs the same role in other fish species. In this study, the full-length cDNAs encoding Secretogranin IIa (SgIIa) and b (SgIIb) were cloned from the brain of orange-spotted grouper. Sequence analysis showed that a 34-amino acid SN peptide (SNa) is present in SgIIa proprotein, and a 33-amino acid SN peptide (SNb) is present in SgIIb proprotein. The two SN peptides share a low degree of similarity but contain the signature YTPQ-X-LA-X7-EL sequence. Real-time PCR showed that two SgII genes are mainly expressed in the brain and pituitary. During ovarian development, the expression levels of two SgII genes in the hypothalamus and pituitary were significantly reduced at the stage when the ovary contained full-grown oocytes. The biological functions of the two SN peptides were further investigated in vitro and in vivo. Both SN peptides could significantly elevate the mRNA levels of Gonadotropin-Releasing Hormone 1 (GnRH1) and 3 (GnRH3) in the hypothalamic fragments and upregulated the expression of Follicle-Stimulating Hormone beta (FSHb) and Luteinizing Hormone beta (LHb) in the pituitary cells. The stimulatory effects on the expression of GnRHs and Gonadotropins were also observed after intraperitoneal injection of SN peptides. Our study indicated that the SgII/SN system has stimulatory effects on the reproductive axis of orange-spotted grouper.

Characterization of the melanocortin-4 receptor gene from Spinibarbus hollandi and the association between its polymorphisms and S. hollandi growth traits

The melanocortin-4 receptor gene (MC4R) is a member of the central melanocortin pathway, which influences development, growth, metabolism, and appetite. In this study, MC4R was cloned and characterized in Spinibarbus hollandi. MC4R DNA is composed of 3068 nucleotides with a 978 nucleotide open reading frame encoding a protein of 326 amino acids. Quantitative real-time polymerase chain reaction (PCR) analysis revealed that MC4R messenger RNA was ubiquitously expressed in tissues, with the most transcriptional abundance in brain and gonad, and that the expression level of MC4R was significantly higher in the lightest group than in the heaviest group of S. hollandi. A primary assessment of sequence variability revealed six single nucleotide polymorphisms (SNPs), among which, four were in the promoter (−698A>G, −679C>T, −326C>T, and −202A>G) and two were in the exon (36A>G and 234C>T). Three SNPs, −698A>G, −679C>T, and 234C>T, were significantly associated with growth traits, two of which, −698A>G and −679C>T, were in complete linkage. The other three SNPs showed no significant associations with any of the growth traits. Our data indicated a significant association between genetic variations in the S. hollandi MC4R and growth traits. Accordingly, the SNPs identified in the MC4R could be used as potential genetic markers in future breeding programs for S. hollandi and other fish.

The complete mitochondrial genome of Acrossocheilus beijiangensis (Cyprinidae, Barbinae).

Abstract Acrossocheilus beijiangensis is a species of freshwater fish in the family Cyprinidae. In this study, the complete mitochondrial genome of A. beijiangensis has been determined using polymerase chain reaction technique. The genome is 16 600 bp in length, it includes 22 tRNA genes, 13 protein-coding genes, two rRNA genes, a D-loop control region, and another non-coding region called replication origin of Light strand (OL). The order of mitochondrial genes was found to be analogous to other vertebrates. The overall base composition of A. beijiangensis, mitochondrial DNA, was calculated and determined to consist of 30.6% A, 24.9% T, 28.1% C, and 16.3% G. Additionally it was found that most of the mitochondrial genes are encoded on the heavy strand except the NADH dehydrogenase subunit 6 (ND6) and eight tRNA genes. The availability of A. beijangesis mitogenome will provide basic data for the systematic categorization of Acrossocheilus sp., as well as the phylogenetic analysis of Cyprinid fishes.