Abstract
Cry proteins are expressed in rice lines for lepidopteran pest control. These proteins can be transferred from transgenic rice plants to non-target arthropods, including planthoppers and then to a predatory spider. Movement of Cry proteins through food webs may reduce fitness of non-target arthropods, although recent publications indicated no serious changes in non-target populations. Nonetheless, Cry protein intoxication influences gene expression in Cry-sensitive insects. We posed the hypothesis that Cry protein intoxication influences enzyme activities in spiders acting in tri-trophic food webs. Here we report on the outcomes of experiments designed to test our hypothesis with two spider species. We demonstrated that the movement of CryAb protein from Drosophila culture medium into fruit flies maintained on the CryAb containing medium and from the flies to the spiders Ummeliata insecticeps and Pardosa pseudoannulata. We also show that the activities of three key metabolic enzymes, acetylcholine esterase (AchE), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) were significantly influenced in the spiders after feeding on Cry1Ab-containing fruit flies. We infer from these data that Cry proteins originating in transgenic crops impacts non-target arthropods at the physiological and biochemical levels, which may be one mechanism of Cry protein-related reductions in fitness of non-target beneficial predators.
Highlights
Transgenic rice lines expressing Cry protein-encoding genes from the bacterium Bacillus thuringiensis (Bt) have recently been developed to control the major lepidopteran pests, the stem borers and leaffolders in China [1], in wake of environmental contamination and pest outbreak due to the continuous use and overuse of broad spectrum pesticides over the past several decades [2]
We posed the hypothesis that the dietary ingestion of Bt protein could influence enzyme activities in spiders acting in tri-trophic food webs
The data presented in this paper strongly support our hypothesis that intoxication with Bt protoxins influences enzyme activities in spiders acting in tri-trophic food webs
Summary
Transgenic rice lines expressing Cry protein-encoding genes from the bacterium Bacillus thuringiensis (Bt) have recently been developed to control the major lepidopteran pests, the stem borers and leaffolders in China [1], in wake of environmental contamination and pest outbreak due to the continuous use and overuse of broad spectrum pesticides over the past several decades [2]. They reported substantial similarity between arthropod communities in experimental Bt rice crops and control non-Bt rice crops Another field study, using three sites in Zhejiang Province, considered three planthopper species and their predator, C. lividipennis [13]. Chen et al (2003a) reported that the transgenic lines TT9-3 and TT9-4, expressing a fused Cry1Ab-Cry1Ac gene, reduced brown planthopper feeding and oviposition behaviors, relative to the nontransgenic parental line, IR72 [14]. They inferred that the transgenic rice lines reduced planthopper fitness. They reported that transgenic rice lines influenced dispersal of planthoppers and leafhoppers in field conditions [15]
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