2.9—All Plant Breeding Causes DNA Scrambling
Transgene insertion in Roundup Ready soybeans causes some local DNA scrambling, but this is similar to DNA scrambling that is widespread in nature.
Analysis of Peer-Reviewed Research:
RNA termination signals are always added to transgene inserts. These are intended to prevent formation of RNA from genetic material lying outside the added DNA insert. It is possible that this deliberately added termination signal may not work with 100-percent efficiency. In such cases some new variant RNA molecules may be produced in a transgenic plant. Genetic changes during evolution are also likely to lead to many new variant RNA molecules being produced in plants. Genetic Roulette does not evaluate risks posed by RNA variants that occur in plants and which are always present in food and feed. It fails to take note that conventional breeding is more likely to produce new and unusual transcripts than is breeding carried out using genetic engineering. No harmful effect of minor abnormalities in RNA transcription are documented by Smith, perhaps because Smith ignores the evidence that these hypothetical transcripts either do not exist, or exist at such low levels, that they are not translated into proteins. It’s worth repeating that for all the speculation, it has been shown that only the single protein that was intended to be introduced can be found in these soybeans. A thorough safety assessment revealed that the GM soybean closely resemble its parent variety in every regard. The Roundup Ready Soybean is the world’s No. 1 GM crop and has been planted on hundreds of millions of hectares without incident and consumed by humans and animals for a dozen years without any observable adverse effect.
1. Normal cells make many minor messages and often fail to stop making messages where they should. There is no evidence that low levels of variant RNA messages resulting from failure to terminate some messages at the intended to termination point have any deleterious effect. The Roundup Ready soybean has been grown for 12 years on hundreds of millions of hectares—it is in fact the world’s No. 1 GM crop. No adverse effects of message read through have been observed.
2. Smith’s arguments are based on the unexpected finding of two small inserts of DNA in Roundup Ready soybeans but no data show that they are translated into protein (Windels P and others 2001, Rang and others 2005). The variant RNA messages are likely to be present in very low concentration and to be rapidly degraded, and are highly unlikely to specify production of a novel protein. When these small fragments were found, safety regulators considered their implications and declared that Roundup Ready soy was safe.
3. There is hard evidence that no unintended aberrant fusion proteins are formed. Smith neglects to tell the reader, or perhaps does not know, that scientists have sensitive methods with which they can detect unintended proteins that might arise from read-through transcripts. These tests demonstrated that only the desired protein is present in Roundup Ready soybeans (Kärenlampi and Lehesranta 2006, Cellini and others (2004)). For all Smith’s “what-ifs”, the evidence says no fusion proteins are actually formed.
4. Plants continually undergo insertions and rearrangements that from fusion proteins and new transcripts, but no adverse effect or harm have ever been attributed to the process. The numerous DNA scrambling events that chromosomes occur in plants are likely to generate similar novel RNA variants and pose similar hypothetical risks to those raised by Smith. Evidence shows that traditional breeding causes more DNA disruption, and therefore has a greater potential of forming new transcripts and new proteins. The extent of widespread scrambling of DNA in plant chromosomes has been discussed earlier, for example in sections 2.1 and 2.2. Radiation exposure is just one cause of this scrambling (Shirley and others 1992, Gorbunova and Levy 1999) and at least 3,000 different mutant plant varieties created by intentional exposure to ionizing radiation are part of the existing food supply (IAEA 2008). Typical examples of widespread genetic variability in conventional crops are rice (Batista and others 2008) and wheat (Baudo and others 2006).
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,
Cellini F and others (2004). Unintended effects and their detection in genetically modified crops. Food and Chemical Toxicology 42:1089-1125. Unintended effects are those outcomes that are totally unexpected and not predictable. This paper focuses on technology for detection of such unexpected outcomes, and this includes metabolomics, proteomics, and transcriptomics. These buzzwords correspond to various forms of chemical fingerprinting.
Gorbunova V and Levy AA (1999). How plants make ends meet: DNA double-strand break repair. Trends in Plant Science 4(7):263-269. Plants have particularly error-prone mechanisms that join together bits of broken chromosomes. These repair mechanisms scramble the DNA at the site at which the chromosomes are joined together during their repair. Radiation is a common cause of broken chromosomes and triggers these processes which scramble plant DNA and cause mutations
IAEA (2008). Mutant plants can boost yields, resistance: IAEA conference (Vienna, Austria). Reports that some 3000 mutant plant varieties from 170 plant species are catalogued by the International Atomic Energy Agency. www.terradaily.com/2007/080812145530.x6uv6k68.html accessed Dec 20 2008
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/prev_issues.cfm.
Rang A, Linke B and Jansen B (2005) Detection of RNA variants transcribed from the transgene in Roundup Ready soybean, European Food Research and Technology 220(3-4):438-443.
Shirley B W Hanley S and Goodman H M 1992. Effects of ionizing radiation on a plant genome: analysis of two Arabidopsis transparent testa mutations. The Plant Cell 4, 333-347. Demonstration that mutations induced by radiation contain radically scrambled DNA.
Windels P, Taverniers I, Depicker A, Van Bockstaele E, De Loose M (2001) Characterisation of the Roundup Ready soybean insert. Eur Food Res Technol 213:107–112
Genetic Roulette Falsely Claims:
Roundup Ready soybeans produce unintentional RNA variations.
- A “stop signal” is placed after the transgene, telling the cell, “STOP TRANSCRIBING AT THIS POINT.”
- The stop is ignored in GM soya, resulting in longer than intended RNA.
- It is transcribed from a combination of the transgene, and adjacent transgene fragment, and a mutated sequence of DNA.
- The RNA is further rearranged into for variations, any of which may be harmful.
- The faulty “stop” signal may have triggered the rearrangements.
- The same “top” signal is used in other crops, and might lead to similar “re-throughs” and RNA processing.
Smith conjectures about theoretical problems that might occur if an RNA termination signal is not totally effective in termination of transgene RNA messages in a particular variety of transgenic soybeans.