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Li Z.,Xiamen University | Hong W.S.,Xiamen University | Qiu H.T.,Xiamen University | Zhang Y.T.,Xiamen University | And 3 more authors.
Fish and Shellfish Immunology | Year: 2016

The mudskipper Boleophthalmus pectinirostris is a burrow-dwelling fish inhabiting intertidal mudflats. During the spawning season, in a spawning chamber located at the center of their burrow, a pair of male and female fish mate and fertilized eggs adheres onto the inner walls and ceiling with filamentous attachments. During 5 days of incubation, the fertilized eggs are kept clean and hatch with a very high hatching rate under the natural conditions filled with microorganisms. This suggests that the male and/or female reproductive tract may synthesize antimicrobial substances to offer protection against microorganisms that may be deleterious to fertility. To study the antimicrobial strategy of this fish in the spawning season, we first cloned the two hepcidin isoforms from B. pectinirostris, and designated them as Hepcidin-1 and Hepcidin-2 based on phylogenetic analyses. Both of these hepcidin isoforms were highly expressed in the liver, but only Hepcidin-1 showed significant change in response to iron overload. Interestingly, these two hepcidin isoforms were expressed in male reproductive tracts, i.e. the testes and seminal vesicles. The monthly expression pattern indicated that Hepcidin-1 transcript levels showed a peak point only in March (before spawning) in the seminal vesicle, while Hepcidin-2 transcript levels were correlated with male reproductive status and reached their highest level in May (the peak spawning period). Under experimental conditions, the expression of these two hepcidin isoforms showed no response to iron overload in the male gonad. However, after lipopolysaccharide injection, the Hepcidin-1 transcript level was significantly up-regulated in the testes and seminal vesicle 6 h post injection, while Hepcidin-2 transcript levels exhibited a clear time-course dependent upregulation pattern and reached the highest levels 24 h post injection. More interestingly, after injection with LHRH-A3, the expression of Hepcidin-2 was significantly up-regulated in both testes and seminal vesicle. Results from in situ hybridization showed that Hepcidin-2 was expressed in the Leydig cells of the testes and in the epithelium of the seminal vesicle. Taken together, the results from our study indicated that these two hepcidin isoforms in the mudskipper may have different functions: Hepcidin-1 may play a dual role in both iron metabolism regulation in the liver and a short antimicrobial response in male reproductive tracts, while Hepcidin-2 is more specialized in reproductive immunity in male reproductive tracts. © 2016 Elsevier Ltd Source

Hong L.Y.,Xiamen University | Hong W.S.,Xiamen University | Zhu W.B.,Xiamen University | Shi Q.,Marine and Fisheries Institute | And 2 more authors.
General and Comparative Endocrinology | Year: 2014

The mudskipper Boleophthalmus pectinirostris, a burrow-dwelling fish inhabiting intertidal mudflats, spawns only once during the spawning season around either the first or last lunar quarters. To understand the molecular mechanisms regulating this semilunar spawning rhythm, we cloned all melatonin receptor subtypes (mtnr1a1.4, mtnr1a1.7, mtnr1b, and mtnr1c). Expression of three melatonin receptor subtypes (except mtnr1c) was found in the ovaries. In contrast, the expression of all receptor subtypes was found in the diencephalon and the pituitary. In the fully-grown follicles, only mtnr1a1.7 mRNA was detected in both the isolated follicle layers and denuded oocytes. Interestingly, the transcript levels of both mtnr1a1.4 in the diencephalon and mtnr1a1.7 in the ovary displayed two cycles within one lunar month, and peaked around the first and last lunar quarters. We used 17α,20β-dihydroxy-4-pregnen-3-one (DHP), a maturation-inducing hormone, as a biomarker to examine the involvement of melatonin receptors in the control of the spawning cycle. Melatonin significantly increased the plasma DHP level 1. h post intraperitoneal injection. Melatonin also directly stimulated ovarian fragments in vitro to produce a significantly higher amount of DHP. Taken together, these results provided the first evidence that melatonin receptors were involved in the synchronization of the semilunar spawning rhythm in the female mudskipper by acting through the HPG axis and/or directly on ovarian tissues to stimulate the production of DHP. © 2013 Elsevier Inc. Source

You X.,Sun Yat Sen University | You X.,Marine and Fisheries Institute | You X.,State Key Laboratory of Agricultural Genomics | Shu L.,State Key Laboratory of Agricultural Genomics | And 19 more authors.
BMC Genetics | Year: 2013

Background: Orange-spotted grouper, Epinephelus coioides, is one of the most valuable fish species in China. Commercial production of orange-spotted grouper could be increased by developing higher growth rates and improving commercially important traits. Information on genetic markers associated with quantitative trait loci (QTL) can be used in breeding programs to identify and select individuals carrying desired traits. A high-density genetic linkage map is the basis for QTL study, and multiplexed shotgun genotyping (MSG) facilitates the development of single nucleotide polymorphisms (SNPs) and genotyping. In this study, the first high-density genetic linkage maps for groupers were generated on the basis of the MSG method.Results: The sex-averaged map contained a total of 4,608 SNPs, which spanned 1581.7 cM, with a mean distance between SNPs of 0.34 cM. The 4,608 SNPs were located in 2,849 unique locations on the linkage map, with an average inter-location space at 0.56 cM. There were 2,516 SNPs on the female map, and the number of unique locus was 1,902. However, the male map contained more numbers of SNP (2,939) and unique locations (2,005). The total length of the female and male maps was 1,370.9 and 1,335.5 cM, respectively.Conclusions: The high-resolution genetic linkage maps will be very useful for QTL analyses and marker-assisted selection (MAS) for economically important traits in molecular breeding of the orange-spotted grouper. © 2013 You et al.; licensee BioMed Central Ltd. Source

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