Scientists from Switzerland and Norway recently found in a unique study that the stress reactions of maize containing the DNA for the MON810 event are not predictable. The researchers found a large variation in the transgene expression and Bt protein content caused by plant genetic background and environmental conditions.

The researchers stated that field-grown Bt maize plants might therefore not always produce high enough doses of Bt protein to kill Bt-resistant insect pests – thus increasing the likelihood of pest resistance to the Bt toxin.

Transgene Expression and Bt Protein Content in Transgenic Bt Maize (MON810) under Optimal and Stressful Environmental Conditions

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Authors: Miluse Trtikova, Niklaus Zemp, Alex Widmer, Angelika Hilbeck


Bt protein content in transgenic insect resistant (Bt) maize may vary between tissues within plants and between plants growing under different environmental conditions. However, it is unknown whether and how Bt protein content correlates with transgene expression, and whether this relationship is influenced by stressful environmental conditions. Two Bt maize varieties containing the same transgene cassette (MON 810) were grown under optimal and stressful conditions. Before and during stress exposure, the upper leaves were analysed for transgene expression using quantitative RT-PCR and for Bt content using ELISA. Under optimal conditions there was no significant difference in the transgene expression between the two investigated Bt maize varieties whereas Bt protein content differed significantly. Transgene expression was correlated with Bt protein content in only one of the varieties. Under stressful environmental conditions we found similar transgene expressions as under optimal conditions but Bt content responded differently. These results suggest that Bt content is not only controlled by the transgene expression but is also dependent on the genetic background of the maize variety. Under stressful conditions the concentration of Bt protein is even more difficult to predict.