The fumigant phosphine is used world-wide and is critically important for the protection of stored commodities from insect and rodent pests. However, heavy reliance on phosphine for many decades has resulted in highly-resistant insects, a situation that threatens the safe and economical long-term use of phosphine. We have successfully used C.elegans as a model system to generate and identify genetic mutations responsible for phosphine-resistance (pre). Following EMS mutagenesis, we have isolated a phosphine-resistant line
pre7 [1] carrying the
wr003 mutation, which confers a 6-fold resistance to phosphine and is inherited as an autosomal recessive element. Using SNP markers, we have mapped the phosphine resistance of
wr003 to an autosomal locus of 96kb in length. Subsequent genetic rescue experiments using genomic DNA microinjection have allowed us to refine this region to a 4.6kb rescuing fragment containing only the
pre-7 gene. Injection of a DNA fragment containing the wild-type
pre7 gene into
wr003 is sufficient to restore the transgenic mutant animals susceptibility to phosphine. Sequencing of this locus from the
wr003 mutant revealed a single nucleotide mutation in
pre-7 resulting in an amino acid change in the PRE7 protein, a conserved mitochondrial enzyme that is involved in metabolism. We have found non-complementation of
wr003 with two other pre lines,
wr001 (
pre1, [1]) and
wr002, and have found single nucleotide substitutions in the coding region of
pre7 in both these mutants. We are currently investigating the metabolic basis of phosphine toxicity, as well as a mechanism of resistance through
pre7 mutation. Interestingly, loss-of-function variants of the human orthologue of
pre7 cause an in-born error of mitochondrial metabolism with neurological consequences. We are particularly interested in exploring pathologic phenotypes, neurological and otherwise, which are due to mutations in
pre7 and that are shared between C.elegans and humans. [1]Cheng et al (2003) Toxicol Sci 73:60-65.