Sustainable use of transgenic plants expressing insecticidal proteins from Bacillus thuringiensis (Bt), depends upon sound management strategies that slow selection for resistance alleles. Current strategies for delaying resistance include a high dose of toxin used in conjunction with a refuge of non-Bt plants and the stacking of multiple toxins in one plant. Both strategies involve the constitutive expression of Bt genes. An alternative, less studied strategy is the use of an inducible promoter that allows Bt expression only during critical periods of crop growth or when the damage threshold has been exceeded, thus allowing the entire crop to serve as a temporary refuge for resistance alleles. To test the feasibility of an inducible promoter, a synthetic cry1Ab gene under control of the chemically inducible PR-1a promoter was introduced into broccoli for control of the diamondback moth, Plutella xylostella. Expression of Bt in PR-1a/cry1Ab plants two days after induction is sufficient to kill both susceptible larvae and heterozygous resistant larvae, indicating that there is not an extended lag time during induction where low levels of Bt production may select for resistance. The time course of protein production, signal transduction and level of insect control are being evaluated in laboratory and greenhouse tests. Use of PR-1a/cry1Ab broccoli and the diamondback moth as a model system will help determine the potential of inducible promoters as a resistant management tool.
Species 1: Lepidoptera Plutellidae Plutella xylostella (diamondback moth)
Keywords: Bacillus thuringiensis, inducible promoter
Back to Ten-Minute Papers, Section F. Crop Protection Entomology
Back to Ten-Minute Papers, Section E, F, Fa, Fb
Back to The 2003 ESA Annual Meeting and Exhibition