Signaling pathways activated by sea bass gonadotropin-inhibitory hormone peptides in COS-7 cells transfected with their cognate receptor.

Results of previous studies provided evidence for the existence of a functional gonadotropin-inhibitory hormone (GnIH) system in the European sea bass, Dicentrarchus labrax, which exerted an inhibitory action on the brain-pituitary-gonadal axis of this species. Herein, we further elucidated the intracellular signaling pathways mediating in sea bass GnIH actions and the potential interactions with sea bass kisspeptin (Kiss) signaling. Although GnIH1 and GnIH2 had no effect on basal CRE-luc activity, they significantly decreased forskolin-elicited CRE-luc activity in COS-7 cells transfected with their cognate receptor GnIHR. Moreover, an evident increase in SRE-luc activity was noticed when COS-7 cells expressing GnIHR were challenged with both GnIH peptides, and this stimulatory action was significantly reduced by two inhibitors of the PKC pathway. Notably, GnIH2 antagonized Kiss2-evoked CRE-luc activity in COS-7 cells expressing GnIHR and Kiss2 receptor (Kiss2R). However, GnIH peptides did not alter NFAT-RE-luc activity and ERK phosphorylation levels. These data indicate that sea bass GnIHR signals can be transduced through the PKA and PKC pathways, and GnIH can interfere with kisspeptin actions by reducing its signaling. Our results provide additional evidence for the understanding of signaling pathways activated by GnIH peptides in teleosts, and represent a starting point for the study of interactions with multiple neuroendocrine factors on cell signaling.

Factors affecting fisher decisions: The case of the inshore fishery for European sea bass (Dicentrarchus labrax).

Fishery management relies on forecasts of fish abundance over time and space, on scales of months and kilometres. While much research has focussed on the drivers of fish populations, there has been less investigation of the decisions made day-to-day by fishers and their subsequent impact on fishing pressure. Studies that focus on the fisher decisions of smaller vessels may be particularly important due to the prevalence of smaller vessels in many fisheries and their potential vulnerability to bad weather and economic change. Here we outline a methodology with which to identify the factors affecting fisher decisions and success as well as quantifying their effects. We analyse first the decision of when to leave port, and then the success of the fishing trip. Fisher behaviour is here analysed in terms of the decisions taken by fishers in response to bio-physical and socio-economic changes and to illustrate our method, we describe its application to the under 10-meter fleet targeting sea bass in the UK. We document the effects of wave height and show with increasing wave height fewer vessels left port to go fishing. The decision to leave port was only substantially affected by time of high tide at one of the four ports investigated. We measured the success of fishing trips by the landings of sea bass (kg) per metre of vessel length. Fishing success was lower when wave height was greater and when fish price had increased relative to the previous trip. Fuel price was unimportant, but a large proportion of the variation in success was explained by variation between individual vessels, presumably due to variation in skipper ability or technical restrictions due to vessel characteristics. The results are discussed in the context of management of sea bass and other small-scale inshore fisheries.

Developing a Virus-Binding Bacterium Expressing Mx Protein on the Bacterial Surface to Prevent Grouper Nervous Necrosis Virus Infection.

Grouper nervous necrosis virus (GNNV) infection causes mass grouper mortality, leading to substantial economic loss in Taiwan. Traditional methods of controlling GNNV infections involve the challenge of controlling disinfectant doses; low doses are ineffective, whereas high doses may cause environmental damage. Identifying potential methods to safely control GNNV infection to prevent viral outbreaks is essential. We engineered a virus-binding bacterium expressing a myxovirus resistance (Mx) protein on its surface for GNNV removal from phosphate-buffered saline (PBS), thus increasing the survival of grouper fin (GF-1) cells. We fused the grouper Mx protein (which recognizes and binds to the coat protein of GNNV) to the C-terminus of outer membrane lipoprotein A (lpp-Mx) and to the N-terminus of a bacterial autotransporter adhesin (Mx-AIDA); these constructs were expressed on the surfaces of Escherichia coli BL21 (BL21/lpp-Mx and BL21/Mx-AIDA). We examined bacterial surface expression capacity and GNNV binding activity through enzyme-linked immunosorbent assay; we also evaluated the GNNV removal efficacy of the bacteria and viral cytotoxicity after bacterial adsorption treatment. Although both constructs were successfully expressed, only BL21/lpp-Mx exhibited GNNV binding activity; BL21/lpp-Mx cells removed GNNV and protected GF-1 cells from GNNV infection more efficiently. Moreover, salinity affected the GNNV removal efficacy of BL21/lpp-Mx. Thus, our GNNV-binding bacterium is an efficient microparticle for removing GNNV from 10‰ brackish water and for preventing GNNV infection in groupers.