Cry1Ab toxin production of MON 810 transgenic maize

Abstract

Levels of Cry1Ab toxin were detected in genetically modified maize of genetic event MON 810 against near isogenic maize as negative control by two commercial immunoassays. The immunoassays were characterized for their cross-reactivity (CR) between Cry1Ab protoxin and activated toxin, and were compared with each other for toxin detection in a reference plant sample. Cry1Ab toxin levels, corrected for active toxin content using the CR values obtained, were monitored in maize DK-440 BTY through the entire vegetation period. The toxin concentration was found to show a rapid rise in the leaves to 17.15 +/- 1.66 microg/g by the end of the fifth week of cultivation, followed by a gradual decline to 9.61 +/- 2.07 microg/g by the 16th week and a slight increase again to 13.51 +/- 1.96 microg/g during the last 2 weeks due to partial desiccation. Similar but lesser fluctuation of toxin levels was seen in the roots between 5.32 +/- 0.49 microg/g at the less differentiated V1 stage and 2.25 +/- 0.30 microg/g during plant development. In contrast, Cry1Ab toxin levels appeared to be stably 1.36 +/- 0.45, 4.98 +/- 0.31, 0.47 +/- 0.03, and 0.83 +/- 0.15 microg/g in the stem, anther wall, pollen, and grain, respectively. Toxin concentrations produced at the VT-R4 phenological stages under actual cultivation conditions were compared with each other in three different years within an 8-year period.

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

“…Nevertheless, we noticed that the concentrations of the Cry1Ac protein in rice residues were significantly higher than those reported in our previous study (Xiao et al, 2014), and such difference was also observed in transgenic maize expressing the Cry1Ab protein in three different years (Székács et al, 2010). The variation in the Cry protein expression in Bt crops may be caused by differences in the age of the plant material due to different harvest dates for our two-year experiments and year-to-year climate variation, e.g., temperature and rainfall .…”

The end of a myth—Bt (Cry1Ab) maize does not harm green lacewings

“…The amount of Cry1Ab in leaves of the different transformation events typically ranges from 1 to 17 μg/g fresh weight (FW) (Obrist et al, 2006a; Nguyen and Jehle, 2007; Székács et al, 2010). In contrast, Cry1Ab levels in pollen significantly differ among events.…”

Chronic Responses ofDaphnia magnaUnder Dietary Exposure to Leaves of a Transgenic (Event MON810) Bt–Maize Hybrid and its Conventional Near-Isoline

“…In MON810 maize, the cry1Ab gene is truncated, and according to the manufacturer, codes for a pre-activated 91-kD truncated rCry1Ab toxin (CERA, 2015). The rCry1Ab toxin is expressed continuously but in different quantities in various tissues in transgenic maize throughout the life cycle of the plant (Székács et al, 2010a), creating a different exposure scenario for nontarget organisms than occurs through either pro-toxin expression by the bacterium itself or as used in pesticidal Bt sprays.…”