Friday, December 16, 2005

Follow-up debate from Cell Biologist Professor David Schubert' s comments.

Cell Biologist Professor David Schubert has expressed a nicely put different perspective of GM food in the top Journal Nature Biotechnology:

A different perspective on GM food

As with good weblog postings, the comments and rejoinders to this contribution are at least as important as the initial posting. Nature Biotechnology carried these:
Divergent perspectives on GM food
Reply to 'Divergent perspectives on GM food'

Fortunately, the debate on Schuberts perspective continues unabated today. The following collection are some recent interesting remarks on Agbioview:

AgBioView from December 14, 2005
Re: Schubert - Is Plant Breeding Different from GM?
Martin Mieschendah,

There is no doubt than genetic engineering breeding may lead to unintended effects (see e.g. Table. 6 in H. Kuiper et al.: Assessment of the food safety issues related to genetically modified foods, The Plant Journal 27(6), 503-528, 2001). But these risks are not different from those of conventional breeding.

To my knowledge so far only conventional bred plant varieties causing negative effects to the consumers have found its way to the market and had to be withdrawn. These were the potato variety Lenape that contained very high levels of toxic solanine, a pest-resistant celery variety that caused rashes in agricultural workers as it contained seven-fold more of the carcinogen psoralen than the control celery, and a traditionally bred squash that caused food poisoning (see e.g. AG Haselberger: Codex guidelines for GM food include the analysis of unintended effects, Nature Biotechnology 21-7, 739-741, 2003).

Favorite Papers for 2005: Safety in Conventional Status Quo? From Wayne Parrott

This past year I have been setting aside some papers that have crossed my desk. They caught my attention because they highlight the normal behavior of plants and agroecosystems. Everyone of these papers is about NON-transgenic crops and conventional agriculture. They caught my attention because if any single one of these had been associated with transgenes, an uproar would likely have ensued.

I wanted to call these to your attention because they highlight the lack of perspective and the double standard that continues to persist in the field. I've added my editorial remarks after each title. Enjoy.


Can almond nectar & pollen poison honey bees? (Kevan & Ebert. 2005. Am. Bee J. June 507-509)
- Yes, the pollen is toxic.

Mediation of pathogen resistance by exudation of antimicrobials from roots (Bais et al., 2005.Nature 434:217-221)
- Plants make and secrete toxins into the soil that kill potential pathogens

Reduced fitness of the Colorado potato beetle on potato plants grown in manure-amended soil (Alyokhin & Atlihan. 2005. Environ. Entomol. 34:963-968)
- Nice organic fertilizer can have negative impacts on potato beetles. Who knows what happens to those poor critters who depend on potato beetles for their livelihood.

Long-term effects of crop management on Rhizobium leguminosarum biovar viciae populations. (Depret et al., 2004. FEMS Microbiol. Ecol. 51:87-97)
- Normal crop rotations can alter soil microbial populations-- my guess is far more than Bt exudates ever could.

Copper amendment of agricultural soil selects for antibiotic resistance in the field. (Berg et al., 2005. Lett. Appl. Microbiol. 40:146-151)
- Perhaps Cornell's Environmental Impact Quotient should be amended to increase copper's hazards?

Andrew Apel comments on this further:
In regulatory matters, the doctrine of substantial equivalence has acted more or less effectively as a counterweight to the precautionary principle. Under the doctrine, if novel products are substantially equivalent to those currently on the market, they can be treated in a substantially equivalent way. However, application of the doctrine has been restricted to food and feed products.

Wayne's "Favorite papers for 2005" and other papers presented here in a similar vein suggest that the doctrine of substantial equivalence deserves to be extended to cover environmental impacts and genetic modifications. This would yield interesting avenues of inquiry and force valid comparisons.

The making of inappropriate comparisons plagues agricultural research. Consistently, trials of novel crops and crop protection products compare trial results to either "organic farming" results, or to "no farming at all" results. Quite credible scientists engage regularly in this sort of "comparison bias," which is inherently weighted against technology, and especially against novel technology. There will always be a side-effect not encountered in "organic farming" or "not farming at all," and if this side-effect is even notionally adverse, the technology being tested automatically becomes questionable.

Extending the doctrine of substantial equivalence to environmental impacts and genetic modifications would get around these improper and often ridiculous comparisons.

So for instance, one might ask, are Bt crops substantially as poisonous to honeybees as almonds? If so, should they be regulated in the same manner as almonds? (Which is to say, not at all)

One might also ask, is the impact of RR crops on soil microflora substantially equivalent to the impact of root-expressed antimicrobials in weed populations? If so, should RR crops be regulated in the same manneras weeds? (Which is to say, not at all)

From: "Roger and Carolyn Morton" Subject: re: Schubert - Is Plant Breeding Different from GM Date: Thu, 8 Dec 2005 00:09:45 +1100

I found the Schubert piece on Is Plant Breeding Different from GM? refreshing in that he actually talks science rather than ideology. However, I have three factual bones to pick.

1. The assertion that the recombination events of conventional breeding are non-mutageneic is wrong. Below are three references where the recombination junctions of mutants produced by convetional breeding have been analysised. This data shows how the recombination events of conventional breeding are mutagenic. And since the production of a conventional plant variety requires many cycles of crossing there will be a large number of mutatgeneic events happening in the production of a conventionally bred variety. Thus, conventional breeding and GM breeding are very similar in this regard.

Anderson PA, Lawrence GJ, Morrish BC, Ayliffe MA, Finnegan EJ, Ellis JG. Plant Cell 1997 Apr;9(4):641-51 Inactivation of the flax rust resistance gene M associated with loss of a repeated unit within the leucine-rich repeat coding region. M Parniske and JDG Jones Proc. Natl. Acad. Sci. USA. 1999 96: 5850-5855 Recombination between diverged clusters of the tomato Cf-9 plant disease resistance gene family D Leister, J Kurth, DA. Laurie, M Yano,T Sasaki, K Devos, A Graner, and P Schulze-Lefert Proc. Natl. Acad. Sci. USA. 1998 95 : 370-375 Rapid reorganization of resistance gene homologues in cereal genomes.

2. Another point I would take issue with is Schubert's assertion kanamycin resistance is uncommon in bacterial pathogens and that we should be wary of kanamycin resistance as a marker gene in plants. Isn't the point of the argument that kanamycin resistant bacteria are everywhere, we eat them all the time and they live in our guts? So how does adding a tiny fraction more kanamycin resistance DNA going to increase any risks? Does Schubert have evidence to refute these facts?

3. I would also call into question Schubert's claim that transpositional mutagensis does not happen in conventionally bred crops. What about corn? Isn't it common knowledge that transposons are mutagenic and active in the corn crop? - reference anyone? I think transposons are probably active in all crop plants - we just have not discovered them. For example a mass screening for rust resistance genes in Flax revealed a mutation that when examined further was discovered to be caused by a flax transposable element (JE. Luck et al Plant Journal 16 p365 1998) It had not been discovered because no-one had done a mass screening in the Flax plant.

Subject: Schubert - Is Plant Breeding Different from GM - post script
Date: Thu, 8 Dec 2005 16:55:57 +1100

Further on Schuberts talk about GM vs conventional breeding. Schubert makes the point that "for the last 10,000 years, humans have selected and bred plants that did not make them sick and promoted their health."

And I agree - we have done this. But what happens when a conventional plant breeder wants to find, say, a new insect or disease resistance gene for her pet crop? She goes out into the populations of wild relatives of her pet crop plant. Wild relatives that have not been subjected to 10,000 years of selection for low toxicity. She then crosses these with her pet crop plant, selects her resistant line and does a few backcrosses to dilute out the "other" genes. Now, what screening is done on this new conventionally bred crop to determine if it still contains toxins from the wild relatives? The answer is NONE. Why is this OK? If Schubert says the GM crops have this hypothetical risk of throwing up toxic metablolites and comounds novel to the diet and that this should require them to be subject to "metabolic profiling" then why shouldn't conventionally bred crops which also have the same hypothetical risk be also subject to the same "metabolic profiling"?

AgBioView from December 9, 2005
From: "Bruce Chassy" Subject: RE: Schubert - Is Plant Breeding Different from GM - post script Date: Thu, 8 Dec 2005 12:54:49 -0600

A response to Roger and Carolyn Morton. Both you and Schubert may have both over-looked the published literature a bit. But rejoice, there's already limited published evidence to support your claim.

See for example:

Gareth S. Catchpole, Manfred Beckmann, David P. Eno, Madhav Mondhe, Britta Zywicki, Janet Taylor, Nigel Hardy, Aileen Smith, Ross D. King, Douglas B. Kell, Oliver Fiehn, and John Draper. 2005. Hierarchical metabolomics demonstrates substantial compositional similarity between genetically modified and conventional potato crops. PNAS 102:14458-14462

This paper demonstrates that transgenic potatoes are virtually identical to their parental counterpart while assorted cultivars of potatoes display much greater metabolic variance. We should be clear, however, that this finding applies to potatoes. More research is needed is needed to determine if these findings can be generalized to all crops or if metabolomic screening could add anything to the safety assessment paradigm. It is quite another question to ask if we need any additional data to make a determination of safety. Food toxicologists, nutritionists and food safety experts who have evaluated the currently employed food safety paradigm are virtually unaminous in saying we do not. A point I will argue further on another day.

It should not be surprising that in spite of what Schubert claims, the people who are actually doing metabolic profiling feel that it is not yet suitable as a safety assessment technique. It is a technique that is both being researched and which they feel may be more useful in research than in regulation. Another way to say this is that Schubert is right in arguing metabolomics could be a powerful technique some day. What its exponents will admit is that we do not yet know for what it will be useful nor do we know how to interpret the results. One could not possibility expect them to make a stronger statement if they want continued funding for their research.

Bruce M. Chassy, Ph.D.
Professor of Nutritional Sciences
University of Illinois at Urbana-Champaign

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