Luca Bucchini, MPH student, John's Hopkins School of Public Health.
I am following the discussion on Bt toxin with amazement. Many things have been said without care or precision.
For example, Cry9c is an example of a heat and digestion resistant Bt toxin (all Bt toxins currently used in US marketed crops are of the Cry group); it is inserted in one of Aventis' GM corn lines currently under US Environmental Protection Agency's scrutiny. This same protein has no history of human exposure (it was not present in the strains used for spraying crops). Even it were, if a protein is expressed in a different system (not the bacteria used for spraying but in the plant itself), one can think of a number of issues (eg, post-translational modifications, quantity), that are and should be addressed.
I do not intend to imply that Cry proteins are allergenic, or, worse, toxic. But I am not aware of any study that has assessed their allergenicity - an impossible task with the available technology, as far as I know. And detection of a new, relatively potent allergen (latex, for example) may take a relatively long time, if based solely on medical reports.
Unfortunately, I do not have the possibility to provide more background here, but I hope someone else soon will.
In the meantime, let me invite everyone to express well meditated and documentable views.
In general, there are concerns that cannot be ruled out with mere impatience. These concerns have not been fully addressed by what is regarded as the most transparent and efficient food regulatory system (the US one). Hopefully, the biotech regulatory system will improve before a GMO capable of exerting adverse health (or environmental) effects is placed on the market.
Let me add a couple of lines on developing countries. With my very limited knowledge of agriculture, I will not even try to enter the discussion on the merits of patented GM products versus traditional crops. I guess much depends on implementation.
I would rather like to address a question to participants from developing countries. Are they willing to take higher risks than their developed counterparts? It is my understanding that Europeans refuse GM crops mostly saying that they do not need them (hard to argue against this, given EU overproduction).
Luca Bucchini, PhD
School of Public Health
Johns Hopkins University, USA
lbucchin@jhsph.edu
[To contribute to this conference, send your message to biotech-room1@mailserv.fao.org For further information on the Electronic Forum on Biotechnology in Food and Agriculture see http://www.fao.org/biotech/forum.asp ]
-----Original Message-----
From: Biotech-Mod1
Sent: Monday, April 17, 2000 11:47 AM
To: 'biotech-room1@mailserv.fao.org'
Subject: Re: IPR for developing countries
Certain parties are very worried about the potential impact of the Terminator gene, and similar systems which stop farmers "brown-bagging" second generations of seed grown from seed purchased from seed companies. This is seen as being immoral on the part of the seed companies.
However, it is an issue of intellectual property rights (IPR), and is the basis of the capitalist system: those that invest in developing a product or technology shall get paid for their creativity, capital risk-taking and simple hard work.
It is no different to software companies demanding to be paid for every copy of their software. Pirate copies of computer software are illegal, so "pirate" seed should be equally illegal. The fact is that it takes 10-20 years, and costs millions of dollars, for a seed company to develop a new plant variety, say of maize. The seed companies are looking for the same protection of intellectual property that every computer software and hardware company in the world assumes is their right under international patent laws. And if this protection does not exist for seed companies, then what incentive have they to develop new varieties ?
No-one is forcing farmers to buy improved varieties from seed companies, whether they are GMO varieties or not. There are still many old-fashioned legacy varieties of virtually all crops. Farmers buy seed of new varieties because they have advantages, say of better yield or better shelf quality; and in the end, a better profit for the farmer. The farmer still has the freedom to buy older, non-GMO varieties, or retain existing landraces.
What is more alarming to me is the increasing loss of diverse germplasm, and especially the "old genes" carried in landraces, which occurs when small-scale farmers abandon their own selection and breeding of farmer varieties because the varieties offered by seed companies are SO much better yielding, at least in the short term. (The huge responsibility facing the seed companies is that they now have to guarantee crop stability, under all conditions, forever, something that genetic engineering is particular weak at doing).
However, it is an irreversible phenomenon, and genebanks do not really solve this problem.
Mark D. Laing
Professor, Plant Pathology, University of Natal, South Africa
laing@micr.unp.ac.za
[To contribute to this conference, send your message to biotech-room1@mailserv.fao.org For further information on the Electronic Forum on Biotechnology in Food and Agriculture see http://www.fao.org/biotech/forum.asp ]
-----Original Message-----
From: Biotech-Mod1
Sent: Monday, April 17, 2000 3:10 PM
To: 'biotech-room1@mailserv.fao.org'
Subject: Photoperiod, temperature and yield
I am Don Wallace, Professor Emeritus of Plant Breeding, Cornell University. Some previous e-mails (e.g Shawn McGuire 31 March; Peter Mwangi) have stimulated me to present the following message: That photoperiod gene activity controls partitioning of photosynthate to the plant organs that become yield and thereby is the strongest control over crop adaptation and yield, even in tropical environments with short daylengths.
My study of physiological genetics of yield has suggested the following about crop yield and photoperiod and temperature.
1. Photoperiod-insensitive alleles instruct for partitioning a large proportion of the photosynthate toward growth of flower buds, pods and seeds (or tubers and roots) that will become yield. Therefore, these organs grow rapidly to develop to flowering and to harvest maturity in relatively few days, and have high yield per day, high harvest index and highest yield for short growing seasons.
2. Photoperiod-sensitive alleles reduce partitioning of photosynthate to yield under high temperatures and synergistically reduce yield more as daylength is longer and sensitivity higher. Such reduction competitively enhances growth of organs not yield, enlarges aerial biomass, days to flowering and harvest maturity, lowers harvest index, but gives highest yield for long enough seasons.
3. At five elevations in tropical Guatemala with unlimited growing season and 13-hour daylength, the most photoperiod-sensitive bean (Phaseolus vulgaris) genotypes flowered latest and gave lowest yield at lowland temperatures, but flowered early and gave highest yield at the highest elevations where low temperature reduced photoperiod gene activity. Yields of insensitive genotypes were the reverse.
4. The Institute of Crop Research for the Semi Arid Tropics (ICRISAT) conducted a multilocation pigeonpea yield trial spanning south to north arid India and measured: a) days to flowering, b) days to maturity, c) aerial biomass at maturity, d) yield, e) biomass/day to maturity, f) yield/day to maturity, g) yield/day of seedfill, the seedfill being estimated as h) days from flowering to harvest maturity, and i) harvest index. The largest Genotype x Environment interaction effect on days to flowering and maturity was the genotype x photoperiod x temperature (GPT) interaction. Control over yield for bean described in (3) was repeated. Photoperiod-gene activity directly controlled partitioning measured as the harvest index. Traits b, c and i account in full for yield of every genotype grown in any world environment.
5. Measurement of a to i listed in (4) indicated photoperiod gene(s) as a QTL without usual QTL methods and gene mapping.
6. Cheapest advance of understanding of how crop adaptation arises and yield is accumulated, including environmental effects, and how to breed for higher yield arises by measuring traits a to i in multilocation yield trials conducted to identify the genotypes the farmer should grow. Simultaneous marker-assisted gene and QTL identifications, and even micro array identification of many gene activities, could indicate the genes and QTL that should be selected for.
7. The following should be recognized. Every gene action requires an environmental resource (CO2, H2O, N, essential mineral) to be acted on. All intraplant molecules have arisen through such prior gene actions. Daylength and temperature are not acted upon. But, the Q10 effect of higher temperature enlarges every gene activity, and more delaying daylength and greater sensitivity to photoperiod enlarge any photoperiod gene activity. Reciprocally, no environmental influence occurs except through gene activity that is limited by non optimal availability of environmental resource(s) or intraplant molecules.
8. Two subsets of gene action jointly control traits a to i. The essential
subset is virtually all the genes. Their integrated activities implement
growth and an autonomous capability to develop to all stages. Any
photoperiod genes inhibit and delay that autonomous development as described
above.
Don Wallace, USA
[To contribute to this conference, send your message to
biotech-room1@mailserv.fao.org
For further information on the Electronic Forum on Biotechnology in Food and
Agriculture see http://www.fao.org/biotech/forum.asp ]
-----Original Message-----
[An American/French Entente Cordiale....Moderator]
Here is the summary we made of a discussion between Dr Bucchini and myself
about Bt
toxins action, human toxicity, and allergies.
LUCA BUCCHINI (LB): I was not aware of that mechanism for the Cry proteins
(chithine
synthesis inhibition) [this was referred to in Romain Berruyer's message of
12 APril...Moderator]. Could you provide some reference?
ROMAIN BERRUYER (RB): I want to apologize: I mistook the effect of Bt
proteins
with
chitinase inhibitors used as a new class of insecticide. Here is the
information I
collected for the moment: Cry proteins (i.e. Bt toxins), after partial
degradation
by insect's proteases, bind to specific receptors on insect gut
epithelium
and
this binding lead to cell destruction and death by septicemia. These
receptors are
insect-specific and, more precisely, insect-family specific. As these
proteins are
receptor-specific, they would not wound human gut cells because these
cells
do not
posses such specific receptors.
LB: And the stomach of mammals is at pH 2. Mmmm...what about
milk-fed infants ?
RB: I'm not a specialist in human physiology, but in first
instance it
seems that milk-fed infants are fed with milk, not with Bt transgenic corn.
I
don't
think that proteins can go through gut, blood, then milk without being
degraded.
LB : Cry proteins have not been inserted in marketed soybean but some
varieties are being field-tested. Can I also add that at least Cry9c (one of
the Bt
toxins), a protein inserted in Aventis' corn, is both heat- and digestion-
stable?
RB : Because of their specificity, it does not seem to me to be
a problem if these proteins are found active in human gut, except
allergies.
Because
Bt crops are commercially used in U.S. today, I suppose and I hope that
allergic
studies have been done. I also suppose that if such allergies have been
demonstrated, these results would have been widely reported, because of
the
atmosphere surrounding transgenic crops.
LB : It is unlikely that Cry protein endangers human health, plus the
evidence
so far does not exist. But I urge caution in this sector. There are
possible
concerns and they have to be addressed. As you say, the main concern is
allergy.
There is at least one study that has found Cry1 highly immunogenic
(Vazquez-Padron
et al. Braz J Med Biol Res 2000 Feb;33(2):147-155). But again this
proves
little.
At this point in time, there is no validated animal test that can
predict
novel
protein allergenicity, and a lack of any epidemiological studies. Cry9c
is a
regulatory nightmare and it may not be approved by federal authorities
(though on
shaky grounds)
RB : The risk of a strong allergic reaction that endangers life is low
and quite
difficult to measure. It depends of the person as much as on the
protein. We eat
every day a huge quantity of different proteins and each different
protein can
cause allergy to a small subset of the population. When the
transgenically-added protein
LB : But let us realize that there are issues, and that the safety of
the
public comes first. About interactions allergic proteins/persons: it is
difficult
to predict what is allergenic, it is easier to know who.
RB : I agree.
Romain Berruyer
Luca Bucchini, PhD
[To contribute to this conference, send your message to
biotech-room1@mailserv.fao.org
For further information on the Electronic Forum on Biotechnology in Food and
Agriculture see http://www.fao.org/biotech/forum.asp ]
607-255-1657
Fax 607-255-6683
dhw3@cornell.edu or PBNews@cornell.edu
From: Biotech-Mod1
Sent: Monday, April 17, 2000 4:54 PM
To: 'biotech-room1@mailserv.fao.org'
Subject: Bt toxins action/human toxicity/allergies
a) is not from a well known allergenic family (like latex proteins,
or ground nut proteins, for example)
b) has been tested not to be allergenic(even if the tests are never perfect)
c) is degraded by heat and/ordigestion,
I don't say that the risk is null, I say it is affordable. For the
specific case of Cry9c, I agree with you: the best is not to approve
cultivars containing
this protein before a better allergenic test is made
Ph-D student, CIRAD
France
and
School of Public Health
Johns Hopkins University, USA