Crustacean hyperglycemic hormone precursor transcripts in the hemocytes of the crayfish Procambarus clarkii: Novel sequence characteristics relating to gene splicing pattern and transcript stability

No abstract

Facilitative glucose transporter 1 (GLUT1) is a transporter protein for glucose transport via the plasma membrane of the cells to provide energy through carbohydrate metabolism. GLUT1 cDNA from Litopenaeus vannamei was obtained and analysed in this study. Full-length GLUT1 cDNA is 2062 bp long and contained a 1506-bp ORF encoding a 502 amino acid protein, a 270-bp 5 0 UTR and a 284-bp 3 0 UTR. When shrimp were under acute low salinity stress, the expression in hepatopancreas, muscle, gill and eyestalk was all up-regulated at 12 h (P < 0.05) and 96 h (P < 0.05), while the expression in the four tissues was all down-regulated at 6 h (P < 0.05) and 48 h (P < 0.05) . The expression in the muscle of shrimp at water salinity of 3 was lower than that at water salinity of 30 independent of dietary carbohydrate levels, while expression in hepatopancreas, gill and eyestalk was up-regulated at 200 and 300 g kg À1 carbohydrate levels. The expression in all tissues fed glucose was up-regulated when compared to the expression in shrimp held at a water salinity of 30. This study suggests that GLUT1 is a conserved protein in L. vannamei, and changes in expression due to environmental salinity and dietary carbohydrate level and source.

Molecular response of carbohydrate metabolism in Litopenaeus vannamei was evaluated at transcriptional level through quantitative real-time PCR analysis. The mRNA expressions of six genes hexose-6-phosphotransferase, pyruvate kinase, phosphoenolpyruvate carboxykinase, crustacean hyperglycemic hormone, glucose transporter and insulin-like growth factors binding protein in the hepatopancreas, muscle, gill and eyestalk were analyzed in shrimp fed different levels of carbohydrate and challenged with acute salinity stress. Among these genes, the relative expression of GLUT1, CHH and IGF-BP in the muscle was lower or nearly the same as the control group regardless of the dietary carbohydrate level. The relative expressions of HK and PK were much higher in the hepatopancreas, muscle, gill and eyestalk at 12 h after salinity stress. The relative expression of PEPCK showed a down-up-down tendency and the expression was much higher in different tissues (except in eyestalk) than in the control from 12 to 24 h after stress. This study indicates that there was no significant dietary carbohydrate regulation in muscle. The glycogen and amino acid in muscle were the main source energy for osmoregulation in L. vannamei when the animals were challenged with acute salinity stress. The muscle and gills were the main osmoregulation organ in shrimp under hypo-saline stress.