Identification of differentially transcribed genes in shrimp Litopenaeus vannamei exposed to osmotic stress and challenged with WSSV virus

The effects of hyposmotic stress and white spot syndrome virus (WSSV) challenge in expression was studied in the marine shrimp Litopenaeus vannamei. Messenger RNA from gills of shrimp submitted to osmotic stress was isolated to identify genes differentially expressed through the suppressive subtractive hybridization (SSH) method. Two subtractive libraries forward and two reverse were constructed to identify up and down-regulated genes under these conditions. About 192 clones were sequenced, of which 46 genes were identified. These genes encode proteins corresponding to a wide range of biological roles, including defense, cell signaling, electron transfer, cell proliferation and differentiation, apoptosis, intermediary metabolism, cytoskeleton and digestion. Among the identified genes, 19 were up-regulated and 27 were down-regulated in the animals kept at a lower ion concentration. We evaluated the expression of eight genes by RT-qPCR in shrimp submitted to hyposmotic conditions with and without WSSV challenge. The SSH enabled the identification of genes that are influenced by hyposmotic stress. A significant up-regulation was observed in lectin-C, QM, TGF beta inducible nuclear protein 1, ciclophilin, malate dehydrogenase, mitochondrial ATP synthase F chain and ATP synthase subunit 9 precursor transcripts. However, the expression of these genes in L. vannamei was not affected by WSSV infection both at isosmotic and hyposmotic conditions.