An international team of researchers has developed a new technique for increasing pest resistance in transgenic crop plants, they report this week in PNAS. The strategy, which boosts and broadens the activity of Bacillus thuringiensis (Bt) toxins, targets previously impervious pest species and reduces by up to 1000-fold the level of toxin expression needed, said coauthor Paul Christou at the University of Lleida in Spain.

Heavy use of Bt insecticides worldwide has raised concern that insects might evolve resistance to Bt crops. Strategies to avoid the evolution of resistance include expressing multiple Bt toxins at high doses or fusing Bt toxins together, with resistance in both approaches requiring the unlikely acquisition of multiple simultaneous mutations. Christou and colleagues in Zimbabwe, Uganda, and Britain instead devised a new strategy that increases the repertoire of toxin-binding sites a Bt toxin attacks.

They fused the sequence for Bt toxin Cry1Ac with that...

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