Expression of Cry3Bb1 in transgenic corn MON88017.

To evaluate the effects of transgenic expression of Coleopteran-specific Bt protein Cry3Bb1 on target and nontarget insects in fields with Bt crops, it is necessary to quantify the Cry3Bb1 contents in the plants. Here, we describe the optimization and validation of the quantitative detection of Cry3Bb1 by adapting the commercially available qualitative PathoScreen double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) for quantitative measurements. The optimized method had an average accuracy of 84-109% and was used to quantify the Cry3Bb1 contents of different tissues of Bt corn MON88017 at four developmental stages during three years (2005-2007) in a field trial in Germany. The Cry3Bb1 contents were determined based on both dry weight and fresh weight. Cry3Bb1 expression was highest in young leaves (228.4 microg/g dw and 35.5 microg/g fw) and lowest in pollen (3.8 microg/g fw). In root tissues, the Cry3Bb1 content declined during the growing season from 130 to 40 microg/g dw. A significant decline of Cry3Bb1 contents was also observed during the growing season in other plant tissues. The Cry3Bb1 contents of different plant tissues strongly correlated to each other. On the basis of the total corn biomass produced on 1 hectare, it was estimated that up to 905 g of Cry3Bb1 is produced per hectare Bt corn MON88017.