Evaluation of a chemically inducible promoter for developing a within-plant refuge for resistance management.
Chemically inducible production of Bacillus thuringiensis (Bt) toxins in transgenic plants may provide considerable benefits in preventing or delaying the evolution of insect resistance to Bt crops by creating within-plant temporal refuges. We examined the effect of inducible cry1Ab expression on survival of different genotypes (RR, RS, and SS) of diamondback moth, Plutella xylostella (L.), in transgenic broccoli, Brassica oleracea L., plants transformed with a PR-1a/cry1Ab expression cassette. Spraying leaves of these plants with the inducer acibenzolar-s-methyl [= benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester] (ASM) resulted in high levels of Bt toxin, and detached leaves from fully induced plants caused 100% mortality to all instars of P. xylostella SS and RS genotypes. When plants infested with larvae were treated with ASM, only a few larvae that were nearing completion of their development were able to survive the induction process. Signal transduction from ASM-treated leaves to new plant tissue also was evaluated using a larval assay. New foliage that emerged after plants were induced remained toxic to > or = 80% of RS larvae up to the fourth new leaf. In whole plant tests, however, induced plants remained protected from larval damage for > or = 3 wk. Uninduced PR-1a/cry1Ab plants seemed to produce low levels of Bt that were undetected by an enzyme-linked immunosorbent assay but that resulted in significant fitness costs for susceptible insects. The suitability of PR-1a/cry1Ab broccoli plants for insect resistance management and the requirements of an appropriate inducible promoter are discussed.
Department of Entomology, Cornell University, New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456, USA.
Sarah L
SL
Bates
Jun
J
Cao
Jian-Zhou
JZ
Zhao
Elizabeth D
ED
Earle
Richard T
RT
Roush
Anthony M
AM
Shelton
D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D001937:Brassica / Q000235:genetics*; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva; D009036:Moths / Q000187:drug effects / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020156:Salicylic Acid / Q000494:pharmacology; D015398:Signal Transduction; D013830:Thiadiazoles / Q000494:pharmacology; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D013830:Thiadiazoles; C030956:insecticidal crystal protein, Bacillus Thuringiensis; C099403:S-methyl benzo(1,2,3)thiadiazole-7-carbothioate; D020156:Salicylic Acid