Intestinal uptake of lipovitellin from brine shrimp (Artemia franciscana) by larval inland silversides (Menidia beryllina) and striped bass (Morone saxatilis)

Expression and roles of As-NUPR1 protein from Artemia sinica during embryo development and in response to salinity stress

As-NUPR1, a stress-related protein, plays an important role in post-diapause during embryonic development in the brine shrimp Artemia sinica. In the present study, successful expression of As-NUPR1 from the cDNA sequence isolated from A. sinica was demonstrated using a prokaryotic expression system. The recombinant protein consisted of 132 amino acids with a molecular weight of 15 kDa, and a predicted isoelectric point of 7.17. As-NUPR1 polyclonal antibodies were prepared by immunization of Balb/c mice with purified recombinant As-NUPR1 protein as an antigen, and immunological studies were carried out. Expression of As-NUPR1 during different developmental stages of the embryo and in response to salinity stress was analyzed in A. sinica using Western blots. The experimental results showed that the expression of As-NUPR1 is widely distributed at different developmental stages in A. sinica, and there was no tissue or organ specificity. Expression of As-NUPR1 decreased gradually during the diapause termination stage of embryo development, after which there was a general increase in expression after breaking the shell. In addition, As-NUPR1 expression was highly upregulated under conditions of high salinity. These results suggest that the As-NUPR1 protein is a stress-related protein that plays a role in protecting embryos from high salt damage in different embryonic developmental stages, especially during the post-diapause period.

Molecular analysis and its expression of a pou homeobox protein gene during development and in response to salinity stress from brine shrimp, Artemia sinica

Brine shrimps of the genus Artemia are aquatic species of economic importance because of their important significance to aquaculture and are used as a model species in physiology and developmental biology. Research on Artemia POU homeobox gene function will enhance our understanding of the physiological and developmental processes of POU homeobox gene in animals. Herein, a full-length cDNA encoding an Artemia POU homeobox protein gene 1 (APH-1) from Artemia sinica (designated as As-APH-1) was cloned and characterized by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end (RACE) method. The As-APH-1 gene encoded a protein of 388 amino acid polypeptide with a calculated molecular mass of 42.85kDa and an isoelectric point of 6.90 and the protein belongs to the POU III family. Multiple sequence alignments revealed that A. sinica As-APH-1 protein sequence shared a conserved POU homeobox domain with other species. The early and persistent expression of As-APH-1 in the naupliar stages by semi-quantitative RT-PCR and whole-mount embryonic immunohistochemistry suggest that As-APH-1 functions very early in the salt gland and may be required continuously in this organ. Later in development, expression of As-APH-1 begins to dramatically decrease and disappear in salt gland of the sub-adult Artemia. In addition, we also discovered that As-APH-1 increased obviously as the salinity increased, indicating that As-APH-1 might be used as a good indicator of salinity stress. In summary, we are the first to identify the As-APH-1 gene and to determine its gene expression patterns in early embryogenesis stages and in different salinity stress in brine shrimp, A. sinica. The result of expression of As-APH-1 affected by salinity changes will provide us further understanding of the underlying mechanisms of osmoregulation in Artemia early embryonic development.

Single-cell protein diet of a novel recombinant vitellogenin yeast enhances growth and survival of first-feeding tilapia (Oreochromis mossambicus) larvae

Yeast single-cell protein (SCP) is a high-nutrient feed substitute. This study evaluates the dual applications of a novel recombinant Pichia pastoris SMD1168H (SMD) yeast, expressing a tilapia vitellogenin protein (rVtg), as an SCP diet for Artemia and the first-feeding fish larvae. Instar II Artemia fed rVtg, rVtg precultured in 5% fish oil (rVtg-FO), Saccharomyces cerevisiae (SC), or native SMD had greater lipid contents (P < 0.05) than the freshly hatched. Lipid deposition in the Artemia fed rVtg or rVtg-FO was greater (P < 0.05) than in those fed SMD or SC. Diet-induced accumulation of low levels of docosahexaenoic acid [22:6(n-3)] was detected only in Artemia fed the rVtg-based diets. Tilapia (Oreochromis mossambicus) larvae were fed solely yeast diets singly or in combination (d 3-22), or a staggered regimen of yeast (d 3-12) followed by unenriched or yeast-enriched Artemia (d 13-22). The larvae fed rVtg for 22 d increased in length and weight (P < 0.05), whereas those fed SC or SMD suffered growth suppression and high mortality. Such adverse consequences were ameliorated when 50% of SC was substituted with rVtg. The larvae prefed rVtg followed by a dietary switch to Artemia preenriched for 48 h with rVtg or rVtg-FO were greatest in length, had the highest weight gain, and lived the longest. Besides delivering rVtg protein, essential fatty acids and amino acids, rVtg may have probiotic effects in enhancing larval survival. This study suggests the feasibility of using the rVtg yeast as an Artemia booster and an SCP first feed for larvae.

Purification of vitellin from grass shrimp Palaemonetes pugio, generation of monoclonal antibodies, and validation for the detection of lipovitellin in Crustacea

Much effort has been put into developing vitellogenin antibodies against a wide variety of aquatic vertebrate species to study potential estrogen or anti-estrogen endocrine disrupters. Little work has been done on endocrine disruption in aquatic invertebrates. Although some antibodies have been produced against blue crab and penaeid shrimp lipovitellin, they have only poor cross-reactivity with the important estuarine grass shrimp, Palaemonetes pugio. Vitellin was purified from eggs, monoclonal antibodies were produced using standard techniques, and hybridoma supernatants were screened by ELISA. Western blots were done using extracts from male and female grass shrimp to verify specificity of the monoclonal antibodies. Two low molecular mass bands in the range of 68-85 kD and two high molecular mass bands in the range of 190-221 kD were found. In addition to grass shrimp, several other crustacean species were screened and cross-reactivity found, including blue crab (Callinectes sapidus), mud crab (Rhithropanopeus harrisii), red swamp crayfish (Procambarus clarkii ) and Daphnia magna. To further investigate the use of the antibody, we performed a chronic 6-week pyrene exposure study. We found that vitellin was upregulated in females after 6 weeks and that this may be a protective measure against lipophilic xenobiotics.