Novel mutations in the VKORC1 gene of wild rats and mice – a response to 50 years of selection pressure by warfarin?

<p>Abstract</p> <p>Background</p> <p>Coumarin derivatives have been in world-wide use for rodent pest control for more than 50 years. Due to their retarded action as inhibitors of blood coagulation by repression of the vitamin K reductase (VKOR) activity, they are the rodenticides of choice against several species. Resistance to these compounds has been reported for rodent populations from many countries around the world and poses a considerable problem for efficacy of pest control.</p> <p>Results</p> <p>In the present study, we have sequenced the <it>VKORC1 </it>genes of more than 250 rats and mice trapped in anticoagulant-exposed areas from four continents, and identified 18 novel and five published missense mutations, as well as eight neutral sequence variants, in a total of 178 animals. Mutagenesis in <it>VKORC1 </it>cDNA constructs and their recombinant expression revealed that these mutations reduced VKOR activities as compared to the wild-type protein. However, the <it>in vitro </it>enzyme assay used was not suited to convincingly demonstrate the warfarin resistance of all mutant proteins</p> <p>Conclusion</p> <p>Our results corroborate the <it>VKORC1 </it>gene as the main target for spontaneous mutations conferring warfarin resistance. The mechanism(s) of how mutations in the <it>VKORC1 </it>gene mediate insensitivity to coumarins <it>in vivo </it>has still to be elucidated.</p

Complete nucleotide sequence of Velvet tobacco mottle virus isolate K1

Velvet tobacco mottle virus (VTMoV) infects the native Australian plant Nicotiana velutina, which is endemic to central Australia. This virus is included in the genus Sobemovirus based on virion morphology and serological relationships. We report here the full genome sequence of VTMoV, attained using a genome-walking strategy with both degenerate and specific primers. This sequence confirms that VTMoV is a sobemovirus, with the same open reading frame (ORF) organisation as other described sobemoviruses. The VTMoV sequence is closest to those sobemoviruses isolated from monocotyledonous plants, although the narrow host range of VTMoV is limited to dicotyledonous plants.K. Arthur, S. Dogra and J. W. Randle

Nucleotide sequence diversity in Velvet tobacco mottle virus: a virus with a unique Australian pathosystem

Velvet tobacco mottle virus (VTMoV) is a naturally occurring mirid-transmitted sobemovirus of native velvet tobacco (Nicotiana velutina) plants in the Australian arid zone. We have sequenced the coding region of a typical field isolate of VTMoV (isolate I-17-04, satellite-plus) and show that it differed by nine polymorphisms from the previously sequenced atypical ‘satellite-minus’ variant VTMoV-K1 (represented here as L-K1-04), while retaining the same genomic and amino acid sequence motifs. We also report that although L-K1-04 was confirmed to be free of detectable satellite RNA by gel electrophoretic assay, the satellite sequence was detected in it by RT-PCR assay. Nucleotide sequence variation among the RNA-dependent RNA polymerase open reading frames of 15 field and laboratory isolates identified four phylogenetic groups, but these did not show a pattern related to site or time of sampling. This result would be consistent with nucleotide sequence variants of VTMoV being dispersed widely by migrating adult mirid vectors.K. Arthur, N. C. Collins, A. Yazarlou, J. W. Randle