Transgene expression and Bt protein content in transgenic Bt maize (MON810) under optimal and stressful environmental conditions.

Miluse Trtikova,Odd Gunnar Wikmark,Niklaus Zemp,Alex Widmer,Angelika Hilbeck,M Lucrecia Alvarez

doi:10.1371/journal.pone.0123011

Abstract

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.

Highlights

Genetic modification of crop plants often has the goal to engineer lines that express novel traits that cannot be introduced into the crop by conventional breeding
There was no significant difference in cry1Ab expression in the upper leaves of the two Bacillus thuringiensis (Bt) maize varieties (Table 1)
In the white Bt maize, the transgene expression under cold/wet stress was similar to the expression under optimal conditions, but was significantly reduced under hot/dry stress

Summary

Introduction

Genetic modification of crop plants often has the goal to engineer lines that express novel traits that cannot be introduced into the crop by conventional breeding. Such bioengineering efforts build on the expectation that target gene(s) conferring the desired trait, in association with suitable regulatory elements that are part of the transgene construct, express the desired trait in a stable and reliable manner. One of the two most widely marketed GM traits worldwide is insect resistance, which is conferred by insecticidal toxins from Bacillus thuringiensis (Bt) This trait has been engineered into a number of crop plants, including maize and cotton. Bt maize cultivars derived from the MON810 event contain a transgene cassette consisting of the cauliflower mosaic virus 35S promoter, thet e hsp intron and the cry1Ab gene endowing the resulting MON810 Bt maize plants with a resistance to lepidopteran pest species, the European corn borer, Ostrinia nubilalis

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