2.3—GM Breeding is More Precise than other methods
Scientific investigation shows that there are very few unexpected alterations to gene expression in transgenic plants
Analysis of Peer-Reviewed Research:
Smith’s speculations that transgene insertion disrupts gene expression in genetically modified plants were based on one experiment that was performed with animal cells. This experiment was done using a gene-chip that measures many gene activity levels in cells. A number of similar experiments done with plants demonstrate exactly the opposite. Gene expression studies using gene-chips are very difficult to perform and harder still to reproduce. Small changes in conditions appear to cause large changes in gene expression. Nonetheless, the evidence published in the peer-reviewed literature not cited by Smith shows exactly the opposite of what he claims. It is also the case that scientists try to select modifications that will not disrupt plants, and that after transgenes are inserted, thousands of plants are carefully screened to find plants that have no unintended or unwanted changes. If a genetically engineered plant had suffered drastic changes in gene expression they wouldn’t be normal and wouldn’t be selected.
1. Gene-chip studies in soybean show that transgene insertion is less disruptive than conventional breeding. Gene chips or microarrays are devices that are used to measure the activity levels of tens of thousands of genes. Studies using gene chips to examine perturbation of genes in soybeans revealed that the disturbance from a transgene insertion is much less than the larger disturbances caused by conventional breeding. Typically in cross-breeding trials between different conventional varieties of soybean, it is found that about a thousand genes vary in their activity among the progeny emerging from the cross (Cheng and others 2008).
2. Gene-chip studies in wheat show that the creation of a new GM wheat variety causes fewer changes in gene expression than does conventional breeding. The introduction of a transgene into wheat has been shown to disturb many fewer other genes than when wheat varieties are crossed using conventional cross-pollination breeding methods (Baudo and others 2006).
3. Gene-chip studies in rice show that transgene insertion causes fewer alterations in gene expression than using radiation for crop breeding. Examination of rice using the gene-chip technique reveals there is a much greater disturbance in gene expression from radiation-induced mutations than when a transgene is introduced using genetic engineering (Batista and others 2008).
4. Transgenes cause little disturbance compared with conventional breeding methods. There is an extensive body of evidence now accumulated proving that introduction of a transgene produces relatively little disturbance to the activity of other genes (Di Carli and others 2009, Kärenlampi and Lehesranta (2006), Catchpole GS and others 2005). The yardstick for being able to say confidently that transgene introduction causes a low amount of change is that it has been repeatedly observed that much greater genetic disturbances are routinely seen with conventional breeding techniques than with genetic engineering. Furthermore the process of screening thousands of plants for those with the desired properties during the commercial development of a new crop variety allows breeders to reject any plants that have drastic alterations.
5. Most DNA insertions do nothing. Survey experiments with the model plant Arabidopsis demonstrate that most DNA insertions introduced into this plant using genetic engineering are silent in terms of observable effects (Bouché and Bouchez 2001, El Ouakfaoui Miki 2005) ).
Batista R and others (2008). Microarray analyses reveal that plant mutagenesis may induce more transcriptomic changes than transgene insertion. Proceedings of the National Academy of Sciences of the United States of America 105(9): 3640–3645. Radiation treatment causes more genetic change than does insertion of a transgene.
Baudo MM, and others (2006) Transgenesis has less impact on the transcriptome of wheat grain than conventional breeding. Plant Biotechnol J. 2006 Jul;4(4):369-80.
Bouché N, Bouchez D.(2001) Arabidopsis gene knockout: phenotypes wanted. Curr Opin Plant Biol. 2001 Apr;4(2):111-117 A survey of many insertions shows most DNA insertions do change the plant phenotype.
Catchpole GS and others (2005 ) Hierarchical metabolomics demonstrates substantial compositional similarity between genetically modified and conventional potato crops. PNAS October 4, 2005 vol. 102 no. 40 14458-14462. Another study in which it is found that genetic engineering courses few changes to other genes.
Cheng KC and others (2008) Effect of transgenes on global gene expression in soybean is within the natural range of variation of conventional cultivars. J Agric Food Chem.56(9):3057-67. Gene chip studies show that genetic engineering courses smaller unintended changes than are seen with traditional breeding.
Di Carli and others (2009). Leaf proteome analysis of transgenic plants expressing anti-viral antibodies. Journal Proteome Research 8(2):838-848. Protein profile analysis of transgenic plants shows that very few unexpected changes occur in leaf proteins.
Dubouzet JG, and others (2007). Integrated metabolomic and transcriptomic analyses of high tryptophan rice expressing a mutant anthranilate synthase alpha subunit. J Exp Bot. 2007;58(12):3309-21. Epub 2007 Sep 4. Comprehensive surveys of this study showed that genetic engineering causes relatively little change to other genes.
El Ouakfaoui S, Miki B.(2005) The stability of the Arabidopsis transcriptome in transgenic plants expressing the marker genes nptII and uidA. Plant J. 41(6):791-800. Strong promoters in the transgenes did not affect the other plant genes in this comprehensive survey of gene activity.
Kärenlampi S O and Lehesranta S J (2006) Proteomic profiling and unintended effects in genetically modified crops. ISB News Report January 2006. www.isb.vt.edu/news/2006/news06.Jan.htm
Zhang L, and others 2006 Rpr1, a gene required for Rpg1-dependent resistance to stem rust in barley. Theor Appl Genet. 2006 Sep;113(5):847-55. Epub 2006 Jul 11. this radiation induced mutation caused the activity of many other genes to be disturbed.
Gene insertion creates genome-wide changes in gene expression
1. One study using a micro-array gene chip found that 5 percent of the host’s genes changed their levels of expression after a single gene was inserted.
2. The changes, which are in addition to the deletions and mutations already discussed [by Smith], are not predictable and have not been fully investigated in the GM crops on the market.
3. These massive changes may have multiple health-related effects.
By extrapolating from a single study of genetic disease in human cells, Smith asserts that introduction of a transgene into plants will disturb the activity of large numbers of other genes.