Apple snail
Transcriptome sequencing-aided proteomic analysis of a non-model organism exposed to copper and cadmium
Application of proteomics in ecotoxicology of non-model organisms has been hindered by a lack of genomic resource. In this study, we constructed a large expressed sequence tag (EST) library at a low cost through sequencing the transcriptome of the apple snail Pomacea canaliculata, a non-model organism in order to better identify differentially expressed proteins in this species exposed to copper and cadmium. Proteins were extracted from the juvenile snails that had been exposed to a sublethal concentration of copper or cadmium, and were separated by two-dimensional electrophoresis. Proteins from the non-exposed juveniles were also extracted to serve as control. Differentially expressed protein spots were analyzed by tandem mass spectrometry. Three approaches to protein identification were employed: direct search of public databases, de novo sequencing and homology search, and search our EST-translated protein library constructed through transcriptome sequencing, resulting in the identification of 2, 5 and 11 of the 12 differentially expressed proteins respectively. Among the 11 identified proteins, some function in general antioxidative stress and energy metabolism, whereas others are involved in specific detoxification, signaling transduction and cytoskeleton disruption and may serve as potential biomarkers of toxicity for these two metals. This study has clearly illustrated that transcriptome sequencing can greatly improve proteomic analysis of a non-model organism. As transcriptome sequencing becomes affordable, more transcriptome sequencing-aided proteomic analyses will likely be conducted to elucidate mechanisms of toxicity and detoxification in many other non-model organisms