Suppression subtractive hybridization (SSH) was applied to screen responsively up-regulation genes in hepatopancreas and gill of Litopenaeus vannamei induced by acute hypo-osmotic stress. In the hepatopancreas, 196 clones were randomly selected and sequenced. 131 non-redundant transcripts, corresponding to 41 genes, were found with elevated expressions. They were functionally clustered into eight biological processes which were protein synthesis and processing, carbohydrate metabolism and energy production, transport, cell growth, apoptosis, cytoskeletal component, cell defense and homeostasis, signal transduction, accounting for 26.2%, 14.3%, 16.7%, 4.7%, 4.7%, 2.3%, 11.9% and 7.1%, respectively. When confirmed by real time qRT-PCR, the gene expression levels of MnSOD, glutathione and glutamine synthetase showed significant increases (2.64-folds, 3.44-folds and 2.16-folds, respectively) in hepatopancreas (P<0.05). Totally 81 expressed sequence tags (ESTs) were obtained by random sequencing from the gill SSH cDNA library, and 52 unigenes, including 15 contigs and 37 singlets, after CP3 online matching were gained by clustering and assembling. The sequence alignment results revealed that 30 of them had significant homology to previously identified Genbank database sequences, while 22 unigenes did not match any sequence in the datebase and presumably represented unidentified cDNAs. Functionally, the unigenes were classified into six clusters, including ion channels and transport proteins (1); protein synthesis, translation and transcription factor (2); stress resistance and antioxidant factors (3); energy metabolism (4); signal receptor and transduction (5); cell fibrin and cytoskeletal proteins (6) with proportion of 23.3%, 20.0%, 20.0%, 16.7%, 10.0% and 10.0% respectively. Real time qRT-PCR confirmation revealed significant elevation of Arginine kinase, Carbonic anhydrase and NaK-ATPase-α-subunit expressions (3.73-folds, 2.55-folds and 5.83-folds, respectively) in the gill after acute low-osmotic stress (P < 0.05). These results provided insight into critical physiology processes and pathways constituting the hypo-osmotic stress adaption program in hepatopancreas and gill of L. vannamei.
