Development time and resistance to Bt crops

Abstract

The yeast [PSI+] element represents a new type of genetic inheritance, in which changes in phenotype are transmitted by a 'protein only' mechanism reminiscent of the 'protein-only' transmission of mammalian prion diseases. The underlying molecular mechanisms for both are poorly understood and it is not clear how similar they might be. Sup35, the [PSI+] protein determinant, and PrP, the mammalian prion determinant, have different functions, different cellular locations and no sequence similarity; however, each contains five imperfect oligopeptide repeats-PQGGYQQYN in Sup35 and PHGGGWGQ in PrP. Repeat expansions in PrP produce spontaneous prion diseases. Here we show that replacing the wild-type SUP35 gene with a repeat-expansion mutation induces new [PSI+] elements, the first mutation of its type among these newly described elements of inheritance. In vitro, fully denatured repeat-expansion peptides can adopt conformations rich in beta-sheets and form higher-order structures much more rapidly than wild-type peptides. Our results provide insight into the nature of the conformational changes underlying protein-based mechanisms of inheritance and suggest a link between this process and those producing neurodegenerative prion diseases in mammals.

Delayed resistance to transgenic cotton in pink bollworm

“…We also did not incorporate an observed developmental delay of resistant pink bollworm on Bt cotton relative to non-Bt cotton, which is a component of incomplete resistance (32,39). The tendency of this developmental delay to slow resistance by lowering the reproductive rate of resistant pink bollworm on Bt cotton may be countered by assortative mating associated with developmental asynchrony between resistant adults from Bt cotton and susceptible adults from refuges (32,39,40).…”

“…The tendency of this developmental delay to slow resistance by lowering the reproductive rate of resistant pink bollworm on Bt cotton may be countered by assortative mating associated with developmental asynchrony between resistant adults from Bt cotton and susceptible adults from refuges (32,39,40).…”

Adaptation by Western Corn Rootworm (Coleoptera: Chrysomelidae) to Bt Maize: Inheritance, Fitness Costs, and Feeding Preference

“…Few studies have examined the inheritance (h) of resistance alleles in western corn rootworm, although evidence of nonrecessive inheritance of Cry3Bb1 resistance in western corn rootworm has been found previously (Meihls et al 2008). By contrast, resistance is functionally recessive for P. gossypiella on cotton (Gossypium hirsutum L.) producing Cry1Ac (Liu et al 1999), Plutella xylostella (L.) on broccoli (Brassica oleracea L.) producing Cry1C (Zhao et al 2000), and for Ostrinia nubilalis (Hü bner) on maize producing Cry1F (Pereira et al 2008). For O. nubilalis and for Treatments included Þrst-, second-, and third-instar larvae, neonates exposed to either Bt or non-Bt maize for 48 h before the experiment, neonates given maize roots with glue covering the cut end of the root, neonates given maize roots without glue, and neonates fed Bt maize roots for 1 wk before the experiment.…”

The cost of resistance toBacillus thuringiensisvaries with the host plant ofTrichoplusia ni

“…Despite the successful selection of resistance to Bt in multiple laboratory populations, significant resistance outside of the laboratory has been detected only in populations of Plutella xylostella (review in Ferré & van Rie 2002) and Trichoplusia ni ( Janmaat & Myers 2003). Resistance to Bt is often reported to decline in the absence of selection and therefore it seems likely that Bt resistance is associated with a significant fitness cost Ferré & van Rie 2002) and this has been documented in several cases (Groeters et al 1993Liu et al 1999). Costs of resistance have not always been the case however (Perez & Shelton 1997;Sayyed & Wright 2001).…”