RESUMO
Crustaceans overcome osmotic disturbances by regulating their intracellular concentration of ions and osmolytes. Glycine betaine (GB), an osmolyte accumulated in response to hyperosmotic stress, is synthesized by betaine aldehyde dehydrogenase (BADH EC 1.2.1.8) through the oxidation of betaine aldehyde. A partial BADH cDNA sequence from the white shrimp Litopenaeus vannamei was obtained and its organ-specific expression during osmotic stress (low and high salinity) was evaluated. The partial BADH cDNA sequence (LvBADH) is 1103bp long and encodes an open reading frame for 217 protein residues. The amino acid sequence of LvBADH is related to that of other BADHs, TMABA-DH and ALDH9 from invertebrate and vertebrate homologues, and includes the essential domains of their function and regulation. LvBADH activity and mRNA expression were detected in the gills, hepatopancreas and muscle with the highest levels in the hepatopancreas. LvBADH mRNA expression increased 2-3-fold in the hepatopancreas and gills after 7days of osmotic variation (25 and 40ppt). In contrast, LvBADH mRNA expression in muscle decreased 4-fold and 15-fold after 7days at low and high salinity, respectively. The results indicate that LvBADH is ubiquitously expressed, but its levels are organ-specific and regulated by osmotic stress, and that LvBADH is involved in the cellular response of crustaceans to variations in environmental salinity.
