Working meeting with the members of the biosafety research group. Forward, Prof. Dr. Rubens Nodari and, from left to right: Dr. Sarah Agapito, Jhully Shilena, Francielli Marian, Caroline Zanatta, Rodrigo Schifini e Dr. Rafael Benevenuto.

Researchers from GenØk – Centre for Biosafety and the Federal University of Santa Catarina (UFSC) in Brazil, have identified that glyphosate-based herbicide triggers unintended effects even in genetically modified varieties resistant to these kinds of pesticides. Entitled “Stacked genetically modified soybean harboring herbicide resistance and insecticide rCry1Ac shows strong defense and redox homeostasis disturbance after glyphosate-based herbicide application”, the research has been published in the scientific journal Environmental Sciences Europe and addresses the adverse effects of glyphosate herbicide, such as Roundup, in the metabolism of genetically modified soybean plants.

Two varieties of transgenic soybeans were analyzed in a controlled environment. Photo: Jefferson Mota

The main goal of this research was to investigate if the insertion of more than one transgene (genetic material transferred between two organisms) in the same plant could affect its homeostasis energy and biochemical responses to the stress provided by glyphosate exposure. In a controlled environment, two genetically modified soybean varieties frequently used by the farmers in Santa Catarina were studied: a first variety containing one inserted transgene (the EPSPS transgene, which confers resistance to glyphosate-based herbicides); and a second variety with two inserted transgenes (the same EPSPS, and the rCry1Ac which codifies to an insecticide toxin). The assays have been made from leaves collected 8 hours after the herbicide application.

The molecular analysis conducted revealed that glyphosate-based herbicides cause adverse effects on carbon metabolism and flow, redox metabolism, photosynthesis, as well as the plant defense responses. The results unveil deleterious effects previously observed in the growth and production of transgenic soy. Still, plants with two inserted transgenes showed a more intense stress response.

The authors highlight that advances in the knowledge of the effects on the physiological processes caused by the application of herbicide in genetically modified plants are essential to establish their safety, in addition to allowing a better understanding of deviations in the mode of action of these herbicides.

This research represents a real situation assay, which occurs in the field with the crop transgenic varieties for grain production. «Since we have found differences between the stacked varieties (which combine two or more transgenes) and with the herbicide exposure, we recommend the regulatory agencies to include these same techniques that we have used in this study as a risk assessment criterion», declare Dr. Sarah Agapito-Tenfen, a scientist from GenØk and co-author of this article.

Zanatta, C.B., Benevenuto, R.F., Nodari, R.O. et al. Stacked genetically modified soybean harboring herbicide resistance and insecticide rCry1Ac shows strong defense and redox homeostasis disturbance after glyphosate-based herbicide application. Environ Sci Eur32, 104 (2020). https://doi.org/10.1186/s12302-020-00379-6

Leaf sampling 8 hours after herbicide application. Photo: Rodrigo Sant’anna

Glyphosate-based herbicide “Roundup” application. Photo: Lyon Sojfer

Conventional soybean varieties that which submitted to the herbicide application. The lack of the resistant EPSPS transgene in conventional plants causes damage at first. Later it leads them to death. The first image, on December 15, 2018, illustrates conventional varieties with herbicide applications. The second image illustrates the same plants on December 18, 2018, in which the plants that are alive are conventional controls without the glyphosate-based herbicide application. Photos: Caroline Zanatta.

Temperature, humidity and luminous intensity data collection. Photo: Jefferson Mota