Tuesday, September 11, 2007

Mechanism of the Decrease in Exogenous-Toxin Protein of Transgenic Bt Cotton Grown in Elevated CO2

Dr. Fa-Jun Chen, Department of Entomology, Nanjing Agricultural University, Weigang #1, Nanjing, 210095, China, Dr. Gang Wu, Biological Science and Technology, Wuhan University of Technology, Luoshi lu #122, Wuhan, 430070, China, Dr. Megha Parajulee, Texas Agricultural Research and Extension Center at Lubbock.Texas A&M University, 1102 East FM 1294, Lubbock, TX 79403, and Dr. Feng Ge, State Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Zhong guan cun, Bei sihuan xilu #25, Beijing, 100080, China.

Abstract: In general, significant decrease in exogenous-toxin (i.e. Bt) protein was shown when transgenic Bt cotton grown in elevated CO2. So transgenic Bt cotton must be faced new ecological risk owing to the decrease in Bt toxin content caused by atmospheric CO2 level arising. Three aspects can be presumed the mechanism of Bt toxin content decrease for transgenic Bt cotton grown in elevated CO2, that is, (1) Do increased carbohydrates of transgenic Bt cotton, causing by elevated CO2, dilute the Bt toxin content in plant tissues? (2) Whether elevated CO2 enhance the expression silencing of Bt gene and its special 35S promoter causing by methylation? (3) Increased nitrogen uptake by roots may result N-deficiency for transgenic Bt cotton grown in elevated CO2, which, in turn, limits nitrogen metabolism and Bt gene expression. Moreover, cultivation practices, e.g., spraying special hypermethylation reagents (e.g. 5-azaC) in combination with nitrogen-fertilization supply has been suggested to improve the Bt-gene expression of transgenic Bt cotton effectively to control target-herbivore pests especially in elevated CO2.

Keywords: Elevated CO2, transgenic Bt cotton, mechanism


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