Molecular characterization and expression analysis of elongation factors 1A and 2 from the Pacific white shrimp, Litopenaeus vannamei.

Elongation factors (EF) are abundant cell proteins that play important roles in the metabolism of all multicellular organisms. Here we describe a functional analysis of elongation factor 1-alpha (EF1A) and elongation factor 2 (EF2), from the Pacific white shrimp, Litopenaeus vannamei. Full-length cDNAs of genes corresponding to EF1A and EF2 were obtained that were 1547 and 2729 bp long, with open reading frames encoding 461 and 846 amino acids, respectively. The deduced amino acid sequences of L. vannamei EF1A and EF2 showed high similarity with those from mice, humans, chickens and other shrimps. RT-PCR analysis indicated that mRNA transcripts of EF1A and EF2 are strongly (but differentially) expressed in haemocytes and gill tissue, and at varying levels in other examined tissues, of the shrimps. Levels of both EF1A and EF2 transcripts increased when shrimps were challenged by pH and cadmium stress, but reached maximal levels after different exposure periods. These results indicate that EF1A and EF2 may play distinct, essential roles in the repair of cellular damage induced by pH and cadmium stress.

Calcium, phosphorus and adenylate levels and Na(+)-K(+)-ATPase activities of prawn, Macrobrachium nipponense, during the moult cycle.

Changes in calcium and phosphorus concentrations, adenylate (AMP, ADP and ATP) levels, and ratios and ATPase activities of Macrobrachium nipponense were investigated during the moult cycle. Ca level in the exoskeleton was lowest in early postmoult (stage A), increasing at stages B and through intermoult (stage C) and peaking in premoult (stage D1 and D2). The P concentrations in the exoskeleton and muscle in late premoult and early postmoult stages were higher than those at other moult stages, and were lowest in the intermoult. Muscle adenylate energy charge (AEC) changed with moult stages, and was in agreement with the change in inorganic P level in the muscle. AEC may be a direct indicator of energy metabolic activity during the moult cycle. ATP/ADP and ATP/AMP ratios in premoult and postmoult stages were higher than that in intermoult stage. Na(+)-K(+)-ATPase activities of gills, muscles and hepatopancreatic of prawns were higher in early postmoult and late premoult animals, whereas they were lower in late postmoult, intermoult and early premoult animals. Gill residual ATPase activity was significantly higher in postmoult animals, while the peak value of hepatopancreatic residual ATPase activity appeared in intermoult stage.

Effects of pH on survival, phosphorus concentration, adenylate energy charge and Na(+)-K(+) ATPase activities of Penaeus chinensis Osbeck juveniles.

Penaeus chinensis (Osbeck) juveniles were maintained for 14 days at pH 6.0, 7.0, 7.6, 8.0 and 8.5, respectively. The effects of pH on survival, phosphorus concentration, adenylate energy charge (AEC) and Na(+)-K(+) adenosine triphosphatase (ATPase) activities of prawns were investigated. The results showed that survival of P. chinensis was impaired at low and high pH levels. The total phosphate level and AEC in abdominal muscle increased with pH level in range of 6.0-7.6 reaching the maximum values at pH 7.6. Thereafter, the levels declined with increasing pH level in range of 7.6-8.5. The change of Na(+)-K(+) ATPase activity in gill of prawn was similar to that of total phosphorus content and AEC in muscle of prawn at different pH. The effect of pH on Na(+)-K(+) ATPase activity in the muscle was lower than on that in gill.