Data on an important soil fungus shows that Roundup applications cause disturbances at the cellular level even when no visible effect on the whole organism is apparent
Roundup herbicide caused disturbances in an important soil fungus at the cellular level at doses at which there is no visible effect on the whole organism, according to a new study published by the research team of Christian Vélot, a molecular geneticist at the University of Paris-Sud.
The authors believe that their data “are likely to challenge the concept of ‘substantial equivalence’ when applied to herbicide-tolerant plants”.
The study, published in Environmental Science and Pollution Research, was carried out on a soil fungus called Aspergillus nidulans, which is used as a marker of agricultural soil health. In the study, molecular analyses were carried out to compare quantitatively and qualitatively all the proteins present in the cells of the fungus that were exposed to Roundup, compared with a control of the same fungus that was not exposed to Roundup. The Roundup formulation tested was the "GT Plus" formulation, containing 450g/l of glyphosate, its active herbicidal active ingredient. The exposure dose chosen corresponded to the maximum concentration for which no visible (macroscopic) effect is observed – otherwise known as the NOAEL or No Observed Adverse Effect Level.
Christian Vélot, who led the study, said, “The results show that even at this low dose, Roundup causes a modulation of about 6% of the detected proteins, mainly affecting the process of cellular detoxification and stress response, protein synthesis, protein and amino acids metabolism, and energy and respiratory metabolism.”
Vélot added that the data show that “metabolic disturbances due to pesticide residues may occur at exposure doses for which there are no visible toxic effects, such as the agricultural doses used on Roundup-tolerant genetically modified crops”.
The researchers’ data were obtained with a fungus used as a model organism. But Vélot says the fact that molecular and metabolic effects were observed at doses without visible toxicity suggests that this may also be the case for other organisms, and in particular for Roundup-tolerant GM plants, which are subjected to much higher agricultural doses. “At least,” he said, “it is legitimate and justified, based on our findings, to suspect that.”
In countries around the world, GM crops are evaluated based on the principle that the GM crop may be assumed to be as safe as its non-GM counterpart, as long as the two are similar. But the new data, according to the paper’s conclusion, “confirm… the importance of taking into account the impact of these herbicide residues in the determination process of substantial equivalence, since metabolic disturbances due to these residues may add toxic properties to the final plant product.”
Most of Europe’s farm animals are fed Roundup-tolerant GM soybean meal imported from Brazil and Argentina. It is considered to be substantially equivalent to conventional soybeans. But the authors state in their press release, “Our study reveals the need to undergo detailed molecular and metabolic studies of these genetically modified plants prior to any decision to keep or place them on the market.”
Such analyses would reveal changes at the cellular level that are not visible at the level of the whole organism.
The new study was carried out within the framework of a participatory research project in partnership between the University of Paris-Sud and the associations Générations Futures and the Criigen.
Proteomic analysis of the soil filamentous fungus Aspergillus nidulans exposed to a Roundup formulation at a dose causing no macroscopic effect: a functional study
Poirier F, Boursier C, Mesnage R, Oestreicher N, Nicolas V, Vélot C.
Environ Sci Pollut Res Int. 2017 Sep 23. doi: 10.1007/s11356-017-0217-6. [Epub ahead of print]
Roundup® is a glyphosate-based herbicide (GBH) used worldwide both in agriculture and private gardens. Thus, it constitutes a substantial source of environmental contaminations, especially for water and soil, and may impact a number of non-target organisms essential for ecosystem balance. The soil filamentous fungus Aspergillus nidulans has been shown to be highly affected by a commercial formulation of Roundup® (R450), containing 450 g/L of glyphosate (GLY), at doses far below recommended agricultural application rate. In the present study, we used two-dimensional gel electrophoresis combined to mass spectrometry to analyze proteomic pattern changes in A. nidulans exposed to R450 at a dose corresponding to the no-observed-adverse-effect level (NOAEL) for macroscopic parameters (31.5 mg/L GLY among adjuvants). Comparative analysis revealed a total of 82 differentially expressed proteins between control and R450-treated samples, and 85% of them (70) were unambiguously identified. Their molecular functions were mainly assigned to cell detoxification and stress response (16%), protein synthesis (14%), amino acid metabolism (13%), glycolysis/gluconeogenesis/glycerol metabolism/pentose phosphate pathway (13%) and Krebs TCA cycle/acetyl-CoA synthesis/ATP metabolism (10%). These results bring new insights into the understanding of the toxicity induced by higher doses of this herbicide in the soil model organism A. nidulans. To our knowledge, this study represents the first evidence of protein expression modulation and, thus, possible metabolic disturbance, in response to an herbicide treatment at a dose that does not cause any visible effect. These data are likely to challenge the concept of “substantial equivalence” when applied to herbicide-tolerant plants.