New study reveals safety testing of stacked trait GMOs inadequate

Stacking traits in GM plants has been found to cause unexpected effects, including synergistic effects, which are not investigated in regulatory authorisations. These changes could affect the safety of the GMO.

1. Comment on new study by Claire Robinson of GMWatch
2. Plain English summary of the new study
3. Effect of stacking insecticidal cry and herbicide tolerance epsps transgenes on transgenic maize proteome – study abstract

[Picture above, left to right: Some of the research team: Prof Rubens Onofre Nodari (project coordinator), Dr Sarah Agapito, Vinicius Vilperte, and Rafael Benevenuto]

1. Comment on new study by Claire Robinson of GMWatch

An important new paper has been published that challenges regulators' lax approaches to assessing the risks of GM stacked trait crops.

In Europe, EFSA's approach to regulating stacked trait GMOs is arguably the most stringent in the world, as it requires a full risk assessment even if the single GMO parent varieties have already been approved. The new paper compares EFSA's approach favourably with that of Brazil's regulator, which does not require a full risk assessment if the parent varieties have been approved.

However, in Europe, the stacked trait GM maize SmartStax was approved for food and feed in November 2013 without an investigation of potential combinatorial and synergistic effects between the insecticidal toxins and the residues from herbicide spraying.

Also, EFSA does not require animal feeding studies with the complete stacked trait crop – only with the single-trait GM parent varieties. Testbiotech has reported on how industry and EFSA have systematically undermined the risk assessment of SmartStax maize.

Contrary to EFSA's view, experts from EU Member States such as Austria, Belgium and Germany have advocated the need to carry out feeding studies to test for synergistic effects.

Austrian experts describe it thus: “The safety of all newly expressed proteins in animal models applied simultaneously and combined was not assessed in the dossier. Insecticidal Cry proteins produced by GM plants as well as transproteins conferring tolerance to herbicides constitute a sum of new plant constituents possibly interacting within the organism. So far, there is absolutely no scientific knowledge about such those in the respective new combinations and possibly resulting additive and/or synergistic effects.”

Now a new study has found that stacking herbicide and insecticide transgenes in a stacked trait variety commonly available in Brazilian markets (not SmartStax) induces synergistic effects in the protein profile of the stacked trait GM plant. Also, metabolic pathways that might affect the safety of this stacked GM maize event were changed in the stacked trait crop when compared to the single-trait parent crops.

All this does not in itself prove that the GMO is dangerous. It does, however, show that the safety of stacked trait GMOs cannot be assumed from data on the single trait GMOs that went into a stacked variety. It also shows that each stacked GMO must undergo its own safety assessment and testing, including animal feeding trials. Otherwise new toxins, allergens, or altered nutritional value in the new stacked trait GMO could be missed.

2. Plain English summary of the new study

• The expression of transgenes in stacked GM maize had a statistically significant reduction of about 34% compared to the single trait GM maize. This might have an impact in pest control and herbicide tolerance in stacked GM maize plants.
• Stacking transgenes into GM maize impacts the overall expression of the plant's native genes.
• Two major metabolic pathways were altered at a statistically significant level. These were related to energy/carbohydrate and detoxification metabolism.
• Altered protein levels in stacked GM maize did not fall within the range of the natural variability found in the landrace variety used in this study.
• Observed alteration in metabolic pathways might affect the safety of this stacked GM maize event. The Brazilian regulatory authority did not analyze the proteomic profile of this stacked GM maize event upon approval and therefore did not detect such changes (proteomics is the study of proteins, particularly their structures and functions).
• This is the first study that has analyzed the proteomic profile of a stacked GM event and compared to the single parental GM events. The results suggest that stacking herbicide and insecticide transgenes induces synergistic and antagonistic effects in the proteome of such plants.

3. Effect of stacking insecticidal cry and herbicide tolerance epsps transgenes on transgenic maize proteome

Sarah Zanon Agapito-Tenfen, Vinicius Vilperte, Rafael Fonseca Benevenuto, Carina Macagnan Rover, Terje Ingemar Traavik and Rubens Onofre Nodari
BMC Plant Biology 2014, 14:346
Published: 10 December 2014
http://www.biomedcentral.com/1471-2229/14/346/abstract
(Open access)

Abstract (provisional)

Background: The safe use of stacked transgenic crops in agriculture requires their environmental and health risk assessment, through which unintended adverse effects are examined prior to their release in the environment. Molecular profiling techniques can be considered useful tools to address emerging biosafety gaps. Here we report the first results of a proteomic profiling coupled to transgene transcript expression analysis of a stacked commercial maize hybrid containing insecticidal and herbicide tolerant traits in comparison to the single event hybrids in the same genetic background.

Results: Our results show that stacked genetically modified (GM) genotypes were clustered together and distant from other genotypes analyzed by PCA. Twenty-two proteins were shown to be differentially modulated in stacked and single GM events versus non-GM isogenic maize and a landrace variety with Brazilian genetic background. Enrichment analysis of these proteins provided insight into two major metabolic pathway alterations: energy/carbohydrate and detoxification metabolism. Furthermore, stacked transgene transcript levels had a significant reduction of about 34% when compared to single event hybrid varieties.

Conclusions: Stacking two transgenic inserts into the genome of one GM maize hybrid variety may impact the overall expression of endogenous genes. Observed protein changes differ significantly from those of single event lines and a conventional counterpart. Some of the protein modulation did not fall within the range of the natural variability for the landrace used in this study. Higher expression levels of proteins related to the energy/carbohydrate metabolism suggest that the energetic homeostasis in stacked versus single event hybrid varieties also differ. Upcoming global databases on outputs from 'omics' analyses could provide a highly desirable benchmark for the safety assessment of stacked transgenic crop events. Accordingly, further studies should be conducted in order to address the biological relevance and implications of such changes.