Expressed sequence tag library of the marine green alga Tetraselmis suecica: a focus on stress-related genes for marine pollution

The marine green microalga, Tetraselmis suecica, is an important food source for aquaculture, lipid source for biofuel production, and a potential model organism for toxicity assays because of its rapid growth and ability to produce useful chemicals. In order to gain molecular toxicogenomic insights, we determined expressed sequence tags (ESTs) of T. suecica by pyrosequencing, and attained 741 K reads, including 290 Mb of cDNA information. Upon data processing, 24,651 contigs and 19,072 non-overlapping fragments were acquired and deposited to the NCBI non-redundant and gene ontology databases. Of these, 11,292 contigs and 1848 singletons were annotated. From the EST data, we found that many previously identified stress-responsive protein-coding genes were included. The data were further investigated with a focus on heat shock protein (HSP) gene families, with most characterized HSP genes present in our ESTs. In addition, the expression of HSP70 and HSP90 was significantly increased after T. suecica cells were exposed to metal contaminants. This work expands our understanding of stress-related genomics of T. suecica and further evaluates a potential use of oxidative stress-related genes as biomarkers, in particular HSP involvement in environmental genomics and marine toxicological assessment.