Profiling of differentially expressed genes in hepatopancreas of white shrimp (Litopenaeus vannamei) exposed to long-term low salinity stress

The Pacific white shrimp, Litopenaeus vannamei, is a euryhaline crustacean capable of tolerating a wide range of ambient salinity (0.5-40 psu). To investigate the effect of long-term low salinity stress on gene expression in the hepatopancreas in shrimp, we performed suppression subtractive hybridization (SSH) in juvenile L. vannamei exposed to long-term low salinity. The shrimp (initial body weight, 0.27 +/- 0.01 g) were cultured at salinity 2 psu and salinity 30 psu for 56 days. We then constructed forward and reverse subtractive cDNA libraries. We used bioinformatics tools and vector screening to select a total of 200 (80 from forward, 120 from reverse) randomly selected clones over 100 nucleotides in length for further analysis. Nineteen contigs and 54 singletons were generated from a total of 73 consensuses. The consensuses, upon a sequence homology search using BLASTX (NCBI), revealed that 24.66% (18/73) of them had no significant match to reported sequences in the database, suggesting that they had not previously been found and that they were probably associated with stress-regulated functions. The remaining 75.34% (55/73) of the consensuses encoded proteins were matched to a wide range of functions including immune-related functions, metabolism, ribosomal activity, transfer activity, and apoptosis. The most common group in these SSH libraries was immune-related proteins and enzymes (11/17). Quantitative RT-PCR results confirmed that the relative expression of 5 differentially expressed genes encoding hemocyanin, chitinase, ecdysteroid-regulated protein, trypsin and chymotrypsin 1 was decreased 2-, 1.45-, 11.11-, 1.33- and 1.54-fold, respectively, in the reverse library. This subtractive cDNA library provides a basis for the study of the genetic response of shrimp to environmental stress. (C) 2012 Elsevier B.V. All rights reserved.