Analysis of heat, cold or salinity stress-inducible genes in the Pacific abalone, Haliotis discus hannai, by suppression subtractive hybridization

In order to investigate environmental stress inducible genes in abalone, we analyzed differentially expressed transcripts from a Pacific abalone, Haliotis discus hannai, after exposure to heat-, cold- or hyposalinity-shock by suppression subtractive hybridization (SSH) method. 1,074 unique sequences from SSH libraries were composed to 115 clusters and 986 singletons, the overall redundancy of the library was 16.3%. From the BLAST search, of the 1,316 ESTs, 998 ESTs (75.8%) were identified as known genes, but 318 clones (24.2%) did not match to any previously described genes. From the comparison results of ESTs pattern of three SSH cDNA libraries, the most abundant EST was different in each SSH library: small heat shock protein p26 (sHSP26) in heat-shock, trypsinogen 2 in cold-shock, and actin in hyposalinity SSH cDNA library. Based on sequence similarities, several response-to-stress genes such as heat shock proteins (HSPs) were identified commonly from the abalone SSH libraries. HSP70 gene was induced by environmental stress regardless of temperature-shock or salinity-stress, while the increase of sHSP26 mRNA expression was not detected in cold-shock but in heat-shock condition. These results suggest that the suppression subtractive hybridization method is an efficient way to isolate differentially expressed gene from the invertebrate environmental stress-response transcriptome.