Now that’s I’ve hooked ya with the title, an admission – this essay has nothing to do with Intelligent Design (except in the sense, oft used by ID proponents, that genetic modification is intelligent design). Rather, it’s about an interesting study that compared gene expression in rice plants that had been modified using “modern” genetic engineering with rice plants that had been subjected to more traditional means of introducing variability. The abstract of the article, by Batista et al., is after the fold. Enjoy.
Controversy regarding genetically modified (GM) plants and their potential impact on human health contrasts with the tacit acceptance of other plants that were also modified, but not considered as GM products (e.g., varieties raised through conventional breeding such as mutagenesis). What is beyond the phenotype of these improved plants? Should mutagenized plants be treated differently from transgenics? We have evaluated the extent of transcriptome modification occurring during rice improvement through transgenesis versus mutation breeding. We used oligonucleotide microarrays to analyze gene expression in four different pools of four types of rice plants and respective controls: (i) a γ-irradiated stable mutant, (ii) the M1 generation of a 100-Gy γ-irradiated plant, (iii) a stable transgenic plant obtained for production of an anticancer antibody, and (iv) the T1 generation of a transgenic plant produced aiming for abiotic stress improvement, and all of the unmodified original genotypes as controls. We found that the improvement of a plant variety through the acquisition of a new desired trait, using either mutagenesis or transgenesis, may cause stress and thus lead to an altered expression of untargeted genes. In all of the cases studied, the observed alteration was more extensive in mutagenized than in transgenic plants. We propose that the 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.
So, what’s the scoop? Well, readers who have been concerned by the claims by anti-GMO advocates that genetic modification may lead to unanticipated and harmful changes in gene expression in crop plants may read the abstract, and the paper, with some alarm. But they really shouldn’t. Remember that humans have been introducing mutations – often on massive scales*, even exceeding that mentioned in this study – into their crop plants for millenia. The end result has not been an agricultural or health armageddon. If one is concerned about untargeted, uncontrolled, or unanticipated genetic changes brought about by genetic modification, the moral of the story here is that even very numerous changes will not lead to catastrophe. So this set of readers can rest easy about their “traditionally-bred”, even organic-certifiable crops.
And they may also rest easy about GMO crops. This study (as well as others not mentioned in this essay) shows that the much more modest genetic modifications accomplished by genetic engineers do not lead to massive changes in gene expression. True enough, there are changes. But these are of a scope that is far less than what is seen with other modes of mutagenesis. In a nutshell, this particular concern that is often parroted by anti-GMO advocates is not a concern at all.
The citation: Batista R, Saibo N, Lourenço T, Oliveira MM. 2008. Microarray analyses reveal that plant mutagenesis may induce more transcriptomic changes than transgene insertion. Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3640-5. Epub 2008 Feb 26. doi:
A few related links from the article:
- Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials. [Food Chem Toxicol. 2008]
- Comparative safety assessment of plant-derived foods. [Regul Toxicol Pharmacol. 2008]
- Towards a better bowl of rice: assigning function to tens of thousands of rice genes. [Nat Rev Genet. 2008]
* Readers may wonder why I am generalizing from a study that involves mutagenesis by irradiation. I believe my generalization is justifiable. Recall that a common mode of breeding, one that goes back millenia, is one of incorporating new traits from distantly-related relatives. Wide hybridization constitutes a sort of genomic shock that dwarfs, in its scope, mutagenesis by irradiation; it has the potential to change a large minority, or even a majority, of genes in a plant’s genome. This is good to keep in mind when thinking about the topic of this essay.
The RNA Underworld 