Is the Cry1Ab Protein from Bacillus thuringiensis (Bt) Taken Up by Plants from Soils Previously Planted with Bt Corn and by Carrot from Hydroponic Culture?

Abstract

The uptake of the insecticidal Cry1Ab protein from Bacillus thuringiensis (Bt) by various crops from soils on which Bt corn had previously grown was determined. In 2005, the Cry1Ab protein was detected by Western blot in tissues (leaves plus stems) of basil, carrot, kale, lettuce, okra, parsnip, radish, snap bean, and soybean but not in tissues of beet and spinach and was estimated by enzyme-linked immunosorbent assay (ELISA) to be 0.05 +/- 0.003 ng g(-1) of fresh plant tissue in basil, 0.02 +/- 0.014 ng g(-1) in okra, and 0.34 +/- 0.176 ng g(-1) in snap bean. However, the protein was not detected by ELISA in carrot, kale, lettuce, parsnip, radish, and soybean or in the soils by Western blot. In 2006, the Cry1Ab protein was detected by Western blot in tissues of basil, carrot, kale, radish, snap bean, and soybean from soils on which Bt corn had been grown the previous year and was estimated by ELISA to be 0.02 +/- 0.014 ng g(-1) of fresh plant tissue in basil, 0.19 +/- 0.060 ng g(-1) in carrot, 0.05 +/- 0.018 ng g(-1) in kale, 0.04 +/- 0.022 ng g(-1) in radish, 0.53 +/- 0.170 ng g(-1) in snap bean, and 0.15 +/- 0.071 ng g(-1) in soybean. The Cry1Ab protein was also detected by Western blot in tissues of basil, carrot, kale, radish, and snap bean but not of soybean grown in soil on which Bt corn had not been grown since 2002; the concentration was estimated by ELISA to be 0.03 +/- 0.021 ng g(-1) in basil, 0.02 +/- 0.008 ng g(-1) in carrot, 0.04 +/- 0.017 ng g(-1) in kale, 0.02 +/- 0.012 ng g(-1) in radish, 0.05 +/- 0.004 ng g(-1) in snap bean, and 0.09 +/- 0.015 ng g(-1) in soybean. The protein was detected by Western blot in 2006 in most soils on which Bt corn had or had not been grown since 2002. The Cry1Ab protein was detected by Western blot in leaves plus stems and in roots of carrot after 56 days of growth in sterile hydroponic culture to which purified Cry1Ab protein had been added and was estimated by ELISA to be 0.08 +/- 0.021 and 0.60 +/- 0.148 ng g(-1) of fresh leaves plus stems and roots, respectively. No Cry1Ab protein was detected in the tissues of carrot grown in hydroponic culture to which no Cry1Ab protein had been added. Because of the different results obtained with different commercial Western blot (i.e., from Envirologix and Agdia) and ELISA kits (i.e., from Envirologix, Agdia, and Abraxis), it is not clear whether the presence of the Cry1Ab protein in the tissues of some plants under field condition and in carrot in sterile hydroponic culture was the result of the uptake of the protein by the plants or of the accuracy and sensitivity of the different commercial kits used. More detailed studies with additional techniques are obviously needed to confirm the uptake of Cry proteins from soil by plants subsequently planted after a Bt crop.

Fate and Effects in Soil of Cry Proteins from Bacillus thuringiensis: Influence of Physicochemical and Biological Characteristics of Soil

“…Some of the results of this study [194] in which the Cry1Ab protein was apparently not taken up by plants from soils on which Bt corn had been previously grown, were in agreement with results of Saxena and Stotzky [82,195], who reported no uptake of the Cry1Ab protein, using the Western blot kit from EnviroLogix, by: (1) non-Bt corn, carrot, radish, and turnip grown in soil, in a plant-growth room, on which Bt corn had been grown or which had been amended with purified Cry1Ab protein or ground biomass of Bt corn; or (2) by non-Bt corn grown in sterile hydroponic culture in which Bt corn had previously been grown. However, some other results of this study were not in agreement with those of Saxena and Stotzky [82,195], as the Cry1Ab protein was detected in the tissues of various plants grown on soil previously planted to Bt corn by the Western blot kit from Agdia and by the ELISA kits from Agdia and Abraxis.…”

“…Although this study indicated that some plant species grown in soils on which Bt corn had been grown take up the Cry1Ab protein, albeit in small amounts, more detailed studies with different methods and techniques are obviously needed to confirm this uptake [194]. If confirmed, the risks to the environment of such uptake will need to be evaluated.…”

“…Studies were conducted to determine whether the Cry1Ab protein released in root exudates and from decaying plant residues of Bt corn was taken up by the plants from soil in the field on which Bt corn had previously been grown and by carrot, as a representative root crop, in sterile hydroponic culture to which purified Cry1Ab protein had been added [194].…”

“…The Cry1Ab protein was also detected by Western blot in tissues of basil, carrot, kale, radish, and snap bean but not of soybean grown in soil on which Bt corn had not been grown since 2002; the concentration was estimated by ELISA to be 0.03±0.021 ng/g in basil, 0.02±0.008 ng/g in carrot, 0.04±0.017 ng/g in kale, 0.02±0.012 ng/g in radish, 0.05±0.004 ng/g in snap bean, and 0.09±0.015 ng/g in soybean. The protein was detected by Western blot in 2006 in most soils on which Bt corn had or had not been grown since 2002 [194].…”

Inter-laboratory comparison of Cry1Ab toxin quantification inMON 810maize by enzyme-immunoassay

“…Moreover, Perry et al (2010) erroneously assume that the sensitivity of non-target butterflies Inachis io and Vanessa atalanta to MON 810 pollen is the same, which questions the validity of their mathematical model. Another example to show the importance of exact measurement of Bt toxin is Icoz, Andow, Zwahlen, and Stotzky (2009) that tried to determine the uptake of Bt toxins by various plants after growing Bt maize. They were not able to come to final conclusions and were questioning the accuracy and sensitivity of the available commercial test kits.…”