Department of Integrative Biology

The snail Biomphalaria glabrata kills the blood fluke Schistosoma mansoni by a mechanism involving production of hydrogen peroxide, the enzymatic product of cytosolic Cu/Zn superoxide dismutase (SODI). This enzyme exhibits higher activity in blood cells (hemocytes) from a predominantly resistant strain of B. glabrata than in hemocytes from a susceptible strain. Additionally, B. glabrata SODI polymorphisms have been associated with susceptibility/resistance to the parasite. To address the hypothesis that SODI transcription levels differ in accordance with variation at the SODI locus, quantitative PCR was performed using hemocyte-derived cDNA prepared from SODI-genotyped snails. Here we report that individuals possessing the allele previously associated with resistance to S. mansoni express significantly higher levels of hemocyte SODI transcripts than individuals lacking this allele. A causal relationship between SODI expression and susceptibility/resistance to S. mansoni is supported by the correlation of transcript quantity with data (from a previous study) on the probability of infection. (C) 2007 Published by Elsevier Ltd.