title: Consumption of Bt rice pollen containing Cry1C or Cry2A protein poses a low to negligible risk to the silkworm Bombyx mori (Lepidoptera: Bombyxidae).
abstract: By consuming mulberry leaves covered with pollen from nearby genetically engineered, insect-resistant rice lines producing Cry proteins derived from Bacillus thuringiensis (Bt), larvae of the domestic silkworm, Bombyx mori (Linnaeus) (Lepidoptera: Bombyxidae), could be exposed to insecticidal proteins. Laboratory experiments were conducted to assess the potential effects of Cry1C- or Cry2A-producing transgenic rice (T1C-19, T2A-1) pollen on B. mori fitness. In a short-term assay, B. mori larvae were fed mulberry leaves covered with different densities of pollen from Bt rice lines or their corresponding near isoline (control) for the first 3 d and then were fed mulberry leaves without pollen. No effect was detected on any life table parameter, even at 1800 pollen grains/cm(2) leaf, which is much higher than the mean natural density of rice pollen on leaves of mulberry trees near paddy fields. In a long-term assay, the larvae were fed Bt and control pollen in the same way but for their entire larval stage (approximately 27 d). Bt pollen densities ≥ 150 grains/cm(2) leaf reduced 14-d larval weight, increased larval development time, and reduced adult eclosion rate. ELISA analyses showed that 72.6% of the Cry protein was still detected in the pollen grains excreted with the feces. The low exposure of silkworm larvae to Cry proteins when feeding Bt rice pollen may be the explanation for the relatively low toxicity detected in the current study. Although the results demonstrate that B. mori larvae are sensitive to Cry1C and Cry2A proteins, the exposure levels that harmed the larvae in the current study are far greater than natural exposure levels. We therefore conclude that consumption of Bt rice pollen will pose a low to negligible risk to B. mori.
authors.affiliation: College of Environment and Plant Protection, Hainan University, Haikou, China; State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China; Qiongtai Teachers College, Haikou, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: College of Environment and Plant Protection, Hainan University, Haikou, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: College of Environment and Plant Protection, Hainan University, Haikou, China.
authors.forename: Fengqin
authors.initials: F
authors.lastname: Cao
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Xiuping
authors.initials: X
authors.lastname: Chen
authors.affiliation: Qiongtai Teachers College, Haikou, China.
authors.forename: Lisheng
authors.initials: L
authors.lastname: Cheng
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China; Agroscope, Institute for Sustainability Science ISS, Zurich, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Romeis
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Yunhe
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Yufa
authors.initials: Y
authors.lastname: Peng
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D012831:Bombyx / Q000254:growth & development*; D004731:Endotoxins / Q000235:genetics* / Q000378:metabolism; D005247:Feeding Behavior / Q000502:physiology; D015870:Gene Expression; D006460:Hemolysin Proteins / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000254:growth & development; D031625:Morus; D012275:Oryza / Q000235:genetics* / Q000276:immunology; D018515:Plant Leaves; D030821:Plants, Genetically Modified / Q000276:immunology; D011058:Pollen / Q000235:genetics* / Q000276:immunology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D019076:Transgenes
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D020033:Protein Isoforms; C030956:insecticidal crystal protein, Bacillus Thuringiensis