No so smart Smartstax

January 2015
Image © Greenpeace

Agapito-Tenfen et al.'s study looking at the effects of breeding GM plants together to stack multiple artificial DNA constructs into one crop [1] has thrown a very uncomfortable shadow over Monsanto's 'SmartStax' maize.

Indications from this study are that, even with only two transformation events stacked, there's reduced expression of the novel genes and significant changes in biochemical pathways such as energy-production, detoxification, cellular processes, genetic information processing, and others. If this degree of perturbation happens when only two events are stacked, what is happening in SmartStax which has eight events stacked? 

SmartStax was approved for food and feed use in the EU in 2013, but without any investigation into the combined effects of all its novel DNA. That's very lax GM regulation indeed.
SmartStax maize harbours a very large complement of artificial genes. It's a product of grandparents which have:
  1. two genes for glufosinate herbicide-tolerance contained in two transformation events
  2. four genes for glyphosate herbicide-tolerance contained in a single transformation event
  3. four genes for Bt insecticide 'cry1A.105' contained in a single transformation event
  4. four genes for Bt insecticide 'cry2Ab' contained in a single transformation event
  5. six genes for Bt insecticide 'cry3Bb1' contained in a single transformation event
  6. six genes for Bt insecticide 'cry1Fa2' contained in a single transformation event plus two partial copies elsewhere in the genome
  7. one gene for Bt insecticide 'cry35Ab1'
  8. two genes for Bt insecticide 'cry34Ab1' contained in a single transformation event.

This adds up to 29 genes, but Prof. Joe Cummins writing in Science in Society counted "at least 34 transgenes" in SmartStax, so there are probably a few marker genes or tissue-linkage genes in there too.

That's a huge scope for interactions affecting the novel genes' expression, the plants' energy- and cell-processes plus the wider genome, not to mention unpredicted toxin generation.

On the subject of homologous novel DNA-silencing suspected by Agapito-Tenfen, as a cause of the reduced gene expression, five out of the nine transformation events in SmartStax include versions of the Cauliflower Mosaic Virus (CaMV) promoter. These could be interacting with each other as well as disrupting normal gene function in other parts of the genome. Likewise, two of the nine events include versions of a ubiquitin promoter which could be interacting with each other. Ubiquitin is a family of proteins involved in many basic cell-maintenance activities: the presence of two novel ubiquitin gene promoters could cause extensive disruption to genomic and cell function.

If Agapito-Tenfen's take on gene-stacking effects is correct, and DNA promoter homology suppresses expression of the artifical genes, SmartStax may not be producing anything like the touted herbicide protection nor the Bt toxin levels required for pest protection.

There could be who knows what other extra homologous chunks of non-coding DNA gluing the artificial constructs together and interacting in unpredictable ways. Also, the transfection method, such as Agrobacterium (a plant-pathogen) carrier, could have left homologous genetic calling cards scattered around.

Tell regulators to face facts: SmartStax isn't so smart, but we're not checking up on just how stupid it is.

  • Prof. Joe Cummins, SmartStax Maize a Medley of Transgenes wit Problems, Instute of Science in Society Report 12.04.10
  • Stacking traits in a GMO is found to cause unexpected synergistic effects, GM Watch 2014, 17.12.14

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