Differential gene expression profiles associated with heavy metal tolerance in the soil insect Orchesella cincta.

Field-selected tolerance to heavy metals has been reported for Orchesella cincta (Arthropoda: Collembola, springtails) populations occurring at metal-contaminated mining sites. Metal tolerance in O. cincta is correlated with heritable increase of excretion efficiency, decrease in cadmium-induced growth reduction, and over-expression of the single copy metallothionein (mt) gene. Although mt plays a major role in cadmium (Cd) detoxification an additional number of gene products may be altered in the tolerant phenotype that influence quantitative traits like excretion efficiency and growth. Using suppression subtractive hybridization analysis (SSH) genes were cloned that showed up- or down-regulation in response to Cd. This study reports about 192 SSH derived cDNA clones, of which 49 were confirmed to be differentially expressed after spot blot analysis. After sequence analysis 19 of the 49 differential clones could be annotated. Real-time RT-PCR of a reference culture and tolerant populations revealed significant gene responses upon Cd exposure. The reference culture showed stress induced gene expression, whereas the tolerant animals maintained normal gene expression or down regulation of cDNAs upon Cd exposure. Seven cDNAs with homology to genes involved in cell signaling, transport and programmed cell death showed an interaction between treatment and population.