title: Effects of water management practices on residue decomposition and degradation of Cry1Ac protein from crop-wild Bt rice hybrids and parental lines during winter fallow season.
abstract: Rice is the staple diet of over half of the world's population and Bacillus thuringiensis (Bt) rice expressing insecticidal Cry proteins is ready for deployment. An assessment of the potential impact of Bt rice on the soil ecosystem under varied field management practices is urgently required. We used litter bags to assess the residue (leaves, stems and roots) decomposition dynamics of two transgenic rice lines (Kefeng6 and Kefeng8) containing stacked genes from Bt and sck (a modified CpTI gene encoding a cowpea trypsin inhibitor) (Bt/CpTI), a non-transgenic rice near-isoline (Minghui86), wild rice (Oryza rufipogon) and crop-wild Bt rice hybrid under contrasting conditions (drainage or continuous flooding) in the field. No significant difference was detected in the remaining mass, total C and total N among cultivars under aerobic conditions, whereas significant differences in the remaining mass and total C were detected between Kefeng6 and Kefeng8 and Minghui86 under the flooded condition. A higher decomposition rate constant (km) was measured under the flooded condition compared with the aerobic condition for leaf residues, whereas the reverse was observed for root residues. The enzyme-linked immunosorbent assay (ELISA), which was used to monitor the changes in the Cry1Ac protein in Bt rice residues, indicated that (1) the degradation of the Cry1Ac protein under both conditions best fit first-order kinetics, and the predicted DT50 (50% degradation time) of the Cry1Ac protein ranged from 3.6 to 32.5 days; (2) the Cry1Ac protein in the residue degraded relatively faster under aerobic conditions; and (3) by the end of the study (~154 days), the protein was present at a low concentration in the remaining residues under both conditions. The degradation rate constant was negatively correlated with the initial carbon content and positively correlated with the initial Cry1Ac protein concentration, but it was only correlated with the mass decomposition rate constants under the flooded condition. No Cry1Ac protein was detected in the soils surrounding the buried residue. Our results did not reveal any evidence that the stacked genes (Bt/CpTI) or the presence of the Cry1Ac protein influenced the decomposition dynamics of the rice residues. Furthermore, our results suggested that field drainage after residue incorporation would promote Cry1Ac protein degradation.
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China.
authors: Manqiu
authors: M
authors: Xiao
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China.
authors: Shanshan
authors: S
authors: Dong
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China.
authors: Zhaolei
authors: Z
authors: Li
authors: Institute of Environment, Resources, Soils and Fertilizers, Zhejiang Academy of Agricultural Sciences, 310021 Hangzhou, China.
authors: Xu
authors: X
authors: Tang
authors: Institute of Environment, Resources, Soils and Fertilizers, Zhejiang Academy of Agricultural Sciences, 310021 Hangzhou, China.
authors: Yi
authors: Y
authors: Chen
authors: Institute of Environment, Resources, Soils and Fertilizers, Zhejiang Academy of Agricultural Sciences, 310021 Hangzhou, China.
authors: Shengmao
authors: S
authors: Yang
authors: Institute of Environment, Resources, Soils and Fertilizers, Zhejiang Academy of Agricultural Sciences, 310021 Hangzhou, China.
authors: Chunyan
authors: C
authors: Wu
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China.
authors: Dongxin
authors: D
authors: Ouyang
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China.
authors: Changming
authors: C
authors: Fang
authors: The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, 200433 Shanghai, China. Electronic address: songzp@fudan.edu.cn.
authors: Zhiping
authors: Z
authors: Song
mesh_terms: D057914:Agricultural Irrigation; D001413:Bacillus thuringiensis / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics; D017753:Ecosystem; D004731:Endotoxins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics; D006460:Hemolysin Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics; D007306:Insecticides / Q000032:analysis*; D012275:Oryza / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D010572:Pest Control, Biological; D010573:Pesticide Residues / Q000032:analysis*; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D012621:Seasons; D014867:Water / Q000737:chemistry*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D010573:Pesticide Residues; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D014867:Water
keywords: Bt rice; Crop-wild hybrid; Cry1Ac protein; Ecological risk; Litter decomposition; Water management