Folsomia candida exposed to cadmium spiked soil

Increasing concern about pollution of our environment calls for advanced and rapid methods to estimate ecological toxicity. The use of gene expression microarrays in environmental studies can potentially meet this challenge. We present a novel method to examine soil toxicity. We exposed the collembolan Folsomia candida to soil containing an ecologically relevant cadmium concentration, and found a cumulative total of 1586 differentially expressed transcripts across three exposure durations, including transcripts involved in stress response, detoxification, and hypoxia. Additional enrichment analysis of gene ontology (GO) terms revealed that antibiotic biosynthesis is important at all time points examined. Interestingly, genes involved in the "penicillin and cephalosporin biosynthesis pathway" have never been identified in animals before, but are expressed in F. candida’s tissue. The synthesis of antibiotics can possibly be a response to increased cadmium-induced susceptibility to invading pathogens, which might be caused by repression of genes involved in the immune-system (C-type lectins and Toll receptor). This study presents a first global view on the environmental stress response of an arthropod species exposed to contaminated soil,and provides a mechanistic basis for the development of a gene expression soil quality test. Keywords: cadmium, soil, Collembola, environmental genomics Folsomia candida was exposed to cadmium spiked soil or untreated (reference/control) soil for 2, 4, and 7 days. For each time point 4 biological replicates were used, replicate samples consisted of total RNA extracted from 30 animals exposed in the same jar to either reference or cadmium spiked soil. Cadmium treated samples were always hybridized to reference samples from the same time point, in an evenly distributed dye-swap manner, which resulted in total in 12 hybridizations of 24 samples.