Pusztai on new GM potato study (9/11/2006)

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Pusztai on new GM potato study (9/11/2006)

http://www.gmwatch.org/archive2.asp?arcid=7255

 

GM WATCH COMMENT: We asked Dr Arpad Pusztai what he made of the

following study of GM potatoes by Louise Shepherd and Howard Davies

of the Scottish Crop Research Institute.

 

To understand the points Dr Pusztai makes it's necessary to remind

ourselves of the details of the ground-breaking research Dr Pusztai

conducted, while at the Rowett Research Institute in Scotland, into

the safety of GM potatoes.

 

This research, it may be remembered, found that when rats were fed

on a diet of GM potatoes, they showed stunted growth, reduced immune

function and damage to internal organs.

 

The study's findings, when disclosed on TV, made headlines around

the world, and the Rowett's director, under enormous pressure and in

the face of attacks on Dr Pusztai's integrity, had Pusztai's

laboratory sealed off, his notebooks seized and his research team

disbanded.

 

Dr Pusztai's - then preliminary - materials on his research were

turned over to an audit committee while Dr Pusztai himself was

indefinitely suspended and placed under a gagging order. The audit

committee concluded Dr Pusztai's data did not support the findings

he had claimed.

 

However, other scientists who reviewed the same material concluded

that Dr Pusztai had been dealt with both harshly and unfairly by the

Rowett and its Director. For instance, Professor S. Pierzynowski,

from the Department of Animal Physiology, at Lund University,

Sweden, concluded that " there is enough strong evidence that the

work of the audit group was not objective and [was] per se

dangerous, not only for Dr. Pusztai, but generally for free and

objective science. "

 

Similarly, Dr. Kenneth Lough, a former principal scientific officer

at the Rowett Institute, said, " In my view the evidence presented in

the audit report must be considered as unsafe and is without

justification for use against the scientific reputation of Dr.

Pusztai. "

 

Dr Pusztai's research later passed a stringent peer review process

and was published in The Lancet.

 

However, from the time the news first broke of Dr Pusztai's

findings, claims were repeatedly made by GM supporting scientists

that there was a simple explanation for the intestinal damage found

in the GM-potato-fed rats that had nothing to do with GM. They

argued that Dr Pusztai's findings could be far better explained by

higher levels of glycoalkaloids in the GM potatoes.

 

These claims have continued to be made despite the fact that there

is no data linking glycoalkaloids with this type of gut abnormality.

 

In any case, the GM potatoes used in Dr Pusztai's research actually

contained less glycoalkaloids than the non-GM ones.

 

Here are Dr Pusztai's comments on the Shepherd and Davies study.

---

 

DR ARPAD PUSZTAI:

 

Thank you for sending this piece of news about GM spuds. No, I have

not seen this before because I only look at proper scientific papers

and this is not one. However, for your interest I can tell you a

number of interesting things about this piece of what I regard, at

best, as propaganda material.

 

Davies was one of the members of my " Audit Committee " .

 

Davies just confirmed (without actually referring to the peer

reviewed publication of Nick Birch who originally published this)

that genetic modification did not increase but rather reduced the

toxic solanine alkaloid content of potatoes. This is the final

acknowledgement by the GM lobby that the toxicity of our GM potatoes

could not have been due to the much trumpeted, but falsely claimed,

increase in solanine glycoalkaloids.

 

Potato merchants such as Davies still could not grasp the scientific

concept of what is a true comparison between GM and non-GM. The only

scientifically valid comparison is that made between the GM- and the

isogenic lines grown and harvested under identical conditions and

not a sort of general comparison between potatoes, GM or otherwise.

But how could a committed GM potato breeder ever come to appreciate

the finer points of science?

 

All the best

Arpad

---

 

SEARCHING FOR UNINTENDED COMPOSITIONAL CHANGES IN GE POTATOES

Louise VT Shepherd & Howard V Davies

http://www.isb.vt.edu/news/2006/news06.nov.htm#nov0603

 

GE risk assessment in the European Union

 

Prior to market approval in Europe, genetically engineered (GE)

crops and products undergo a rigorous risk safety assessment based

on a comparative approach. That approach assesses differences

between the GEO and its derived products and their non-GE

counterparts, the counterparts having a history of safe use.1,2 The

risk assessment focuses on a range of parameters, which are

described in the European Food Safety Authority (EFSA) guidance

document.2 Compositional analysis is one of these parameters and the

OECD (Organization for Economic Co-operation and Development) is

providing guidance on which compounds should be targeted for

analysis on a crop by crop basis. The analysis takes into account

the crop-specific profile of compounds with nutritional or anti-

nutritional characteristics. Significant intentional or

unintentional changes in such compounds are likely to drive the need

for more detailed risk assessment.3,4 If a trait or traits are

introduced with the intention of modifying composition

significantly, and where the degree of equivalence cannot be

considered substantial, then the safety assessment of

characteristics other than those derived from the introduced trait

(s) becomes of greater importance. Whilst the potential for using

modern transcriptomic, proteomic, and metabolomic approaches to

assess the potential for detecting unintended effects is under

evaluation (e.g., the EU " SAFEFOODS " project

 

[http://www.safefoods.nl]), the targeted analysis of key nutrients

and anti-nutrients remains the cornerstone of the compositional

evaluations.1

 

GE potato as a case study for compositional analysis

 

Potatoes are the world's fourth most important food crop and have

long been used as a model crop for studies on gene function using

Agrobacterium-mediated transformations. The cultivated potato has

complex genetics (it is tetraploid), and genetic engineering

approaches that add value to existing varieties with a strong

pedigree in other characteristics remain attractive scientifically.

 

The Scottish Crop Research Institute (http://www.scri.sari.ac.uk)

has a history of producing a range of GE potatoes for experimental

purposes; this has afforded opportunities to develop projects on the

use of metabolomics to assess the potential for unintended effects.

 

We feel it is important, however, to use existing OECD guidelines to

establish the baseline against which data on metabolomics can be

compared. In its 2002 " Consensus Document on Compositional

Considerations for New Varieties of Potatoes: Key Food and Feed

Nutrients, Anti-nutrients and Toxicants, " the OECD5 considers that

if the analyses of specific compositional parameters listed in their

document indicate that a novel variety falls within the ranges found

in the literature (apart from intentional modifications resulting

from transgenic approaches) then the variety can be considered

equivalent with respect to its overall composition.

 

In our experiment, metabolite analysis included soluble

carbohydrates, glycoalkaloids, vitamin C, total nitrogen, and fatty

acids. Trypsin inhibitor activity was also assayed. These are the

major compounds recommended by the OECD in its 2002 consensus

document.

 

Range of GE potatoes included

 

Using (primarily) the potato variety Desirée, the study included

transgenic modifications to a range of metabolic and development

processes, including primary carbohydrate metabolism, polyamine

biosynthesis, and glycoprotein processing. The lines included some

with extreme phenotypes, e.g., those with a modified glycoprotein

processing protein (Fig. 1 [see ref. 6]), which produces stunted

plants with poor tuber yield and modified leaf anatomy.

 

Other lines overexpressed a gene that encodes S-adenosylmethionine

decarboxylase (modified polyamine metabolism) and showed significant

increases in tuber number (Fig. 2 [see ref. 7]), whilst yet another

group of transgenics contained starch with amylose levels reduced by

90% (unpublished). All experiments included appropriate controls

consisting of a) wild type non-GE tubers, b) non-GE tubers produced

from plants regenerated through tissue culture (including a callus

phase), and c) GE tubers derived from transformation with an `empty

vector', i.e., no specific target gene included (with the exception

of the kanamycin resistance gene as a selectable marker).

 

What unintended effects were observed?

 

In general the targeted compositional analysis revealed no

consistent differences between GE lines and respective controls. No

construct specifically induced unintended effects. Statistically

significant differences between wild type controls and specific GE

lines did occur but appeared to be random and not associated with

any specific genetic construct. Indeed such significant differences

were also found between wild types and both non-GE, tissue culture

derived, and GE tubers derived from transformation with the empty

vector. More specifically, the study revealed a consistent and

significant increase in vitamin C and a decrease in glycoalkaloids

across many of the GE lines examined, but also in the " control " GE

empty vector lines and in non-GE lines developed through tissue

culture. Somaclonal variation may therefore underpin many of the

compositional changes and may provide a mechanism by

which " unintended " changes in plant composition might occur

independently of the process of transformation and gene insertion

itself. More extensive studies on the impact of tissue culture on

compositional variation are ongoing at the SCRI.

 

Given the range of phenotypes used in this study, it is perhaps

surprising that chemical composition is not affected more

significantly. This indicates that visible, morphological phenotype

is not necessarily a good guide to likely compositional changes.

Similarly, compositional changes may not give rise to an agronomic

phenotype. This is why a holistic and case-by-case analysis of

specific GE lines is required to generate any opinion on potential

risk.

 

In our study the values for specific potato components that we

analyzed (and suggested by the OECD) fall well within published

ranges for potato. It is therefore unlikely that any of the changes

observed would raise issues with regard to food safety or

nutritional value. However, several of these GE lines would not be

considered substantially equivalent to the parent due to phenotypic

perturbations.

 

References

 

1. OECD (1993) Safety evaluation of foods derived by modern

biotechnology: concept and principles.

(http://www.oecd.org/LongAbstract/0,2546,en_2649_34385_1946122_119666

_1_1_1,00.html)

 

2. EFSA [European Food Safety Authority] (2004) Guidance document of

the GMO Panel for the risk assessment of genetically modified plants

and derived food and feed.

(http://www.efsa.eu.int/science/gmo/gmo_guidance/660_en.html).

 

3. Kuiper HA and Kleter GA (2003) The scientific basis for risk

assessment and regulation of genetically modified foods. Trends Food

Sci and Tech 14, 277-293

 

4. Howlett J et al. (2003) The safety assessment of novel foods and

concepts to determine their safety in use. Int J Food Sci Nutr 54

(Supplement), S1-S32

 

5. OECD (2002) Consensus Document on Compositional Considerations

for New Varieties of Potatoes: Key Food and Feed Nutrients, Anti-

Nutrients and Toxicants.

http://www.oecd.org/document/9/0,2340,en_2649_34385_1812041_1_1_1_1,0

0.html

 

6. Taylor MA et al. (2000) A potato alpha-glucosidase gene encodes a

glycoprotein-processing alpha-glucosidase II-like activity.

Demonstration of enzyme activity and effects of down-regulation in

transgenic plants. Plant J 24, 305-316

 

7. Pedros AR et al. (1999) Manipulation of S-adenosylmethionine

decarboxylase activity in potato tubers. Planta 209, 153-160

 

8. Cellini F et al. (2004) Unintended effects and their detection in

genetically modified crops. Food Chem Toxicol 42, 1089-1125

 

Dr Louise VT Shepherd

Post-doctoral Researcher

Quality, Health & Nutrition Programme

Scottish Crop Research Institute

louise.shepherd

Prof Howard V Davies of Science Co-ordination

Scottish Crop Research Institute

howard.davies