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Genetically engineered foods: a threat to human health?
Encontro de Investigadores, Ciência 2009
Rita Batista
Which GM foods are under commercialization in EU?Which GM foods are under commercialization in EU?
5 plant species approved for human consumption:
Soya (drinks, tofu, oil, flour, lecitin…)
Maize (oil, flour, syrup, sweet maize, cereals, etc…)
Oilseed rape (oil)
Cotton (oil)
2 types of genes introduced :
Insect resistance (Cry genes)
Herbicide tolerance/resistance (CP4EPSPS and PAT genes)
Sugar beet (sugar)
What are the major health concerns of GE plants ?What are the major health concerns of GE plants ?
Putative horizontal transferPutative horizontal transfer
Transfer of antibiotic marker genes to gastrointestinal bacteria or bacteria we eat together with food
Natural prevalence of antibiotic resistance in soil and enteric bacteria
DNA breakdown
Recipient bacteria → take up and integrate DNA into their genome
DNA → associated with appropriate regulatory sequences
Transferred trait → confer competitive advantage
Despite:
The concern persists:
Food processing
Passage through gastrointestinal tract
Bacterial restriction enzymes
No scientific evidence for uptake ingested DNA by gastrointestinal bacteria as consequence of food consumption
Putative transgene horizontal transferPutative transgene horizontal transfer
Another concern:
Inactivation of orally administered antibiotic by the resistance markers
Directly
By integration of antibiotic resistance marker genes in gut epithelial cells
most common ARM gene
Rapidly inactivated by stomach acid and degraded by digestive enzymes
From E. coli → ubiquitous in nature
Confers resistance to antibiotics with no therapeutic relevance
Argument of a putative increase of antibiotic resistance by gastrointestinal bacteria due to nptII HT is unacceptable
nptII
Putative transgene horizontal transferPutative transgene horizontal transfer
Inactivation of orally administered antibiotic by marker gene product
By integration of antibiotic resistance marker genes in gut epithelial cells
Gastrointestinal epithelial cells do not divide and have a short life span (7 days)
Integration of antibiotic resistance marker genes in gut epithelial cells would not compromise public health
No expert panel has ever identified a significant risk associated with antibiotic resistance marker genes use
Despite:
Putative transgene horizontal transferPutative transgene horizontal transfer
Efforts aimed to produce ARM free GM plant products
Removal of these genes after transgenic plant selection
Use of intron-containing marker genes
Use of antibiotic resistance plant genes
Consumption of “foreign” DNAConsumption of “foreign” DNA
Consumption of DNA from foreign species (i.e. viruses or bacteria) in the genome of a food plant
Bacteria and viruses always present in our food
All DNAs are chemically equivalent
Potential risk of DNA consumption would not depend on the species of origin → only on its sequence
Consumption of “foreign” DNAConsumption of “foreign” DNA
CaMV35Spro lead to inappropriate over expression of genes in species to which it is transferred?
Consumption of any CaMV-infected vegetables result in ingestion of far more copies of 35S pro than consumption of
transgenic plants carrying this promoter
Several barriers would limit potential interaction of CaMV35Spro with human DNA
CaMV is present in 10% cabbages and cauliflowers
CaMV infects most plant cells and produces 105 particle per cell (each with one copy of 19Spro and 35Spro)
Unexpected alterations in nutritional compositionUnexpected alterations in nutritional composition
GE cause unexpected and/or undesired effects in nutritional composition of final product?
Concern also valid for plants obtained through conventional breeding techniques
GM foods nutritional and biochemical characteristics are tested before its commercialization
Allergenicity/ toxicityAllergenicity/ toxicity
To date, no experimental evidence has supported a higher degree of toxicity/ allergenicity of approved GE foods as
compared to their non-transgenic counterparts
Products of introduced genes represent allergens and/or toxins or induce unintended effects on plant metabolism that lead to upregulated expression of allergens and/or toxins?
Studies claiming for higher toxicity/ allergenicity of GE foods tainted with important flaws
Two allergenicity problems promptly detected by regulatory systems
Pioneer Hi-Bred GE soybean variety
Aventis Starlink GE maize variety
What are our major research interests in this issue?What are our major research interests in this issue?
Are GM foods more allergenic than conventional?Are GM foods more allergenic than conventional?
Does genetic engineering provoke more alterations Does genetic engineering provoke more alterations than other modern conventional breeding techniques?than other modern conventional breeding techniques?
How important is natural plant variability in the How important is natural plant variability in the context of the food safety assessment process?context of the food safety assessment process?
Develop highthrouput methodologies to check for the safety of genetically modified foods
Contribute to fill the lack of scientific data
What have been the major conclusions obtained so far?What have been the major conclusions obtained so far?
None of the tested products have presented increased None of the tested products have presented increased allergenicity after genetic modificationallergenicity after genetic modification
Transcriptome alterations due to genetic modification were Transcriptome alterations due to genetic modification were < for transgenic < for transgenic vsvs mutagenized plants mutagenized plants
Safety assessment of improved plant varieties should be carried out on a case-by-case basis
and not simply restricted to foods obtained through genetic engineering
Probability of an individual having eaten GM food near Probability of an individual having eaten GM food near 100%100%
The beginning…