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Re: Risks GE-food vs. Conventional breeding



Wytze wrote (full message follows after my signature)

>Why do many people claim that conventional breeding is safe? This is
>our common history! Mankind has learned over the past 10,000 years or
>so which plants how to use in the ways these plants are good or at
>least not harmful to our health.

This doesn't proof that conventional breeding (CB) is safe. It just
shows that some products of CB are safe. It doesn't guarantee that
plants produced by CB can't be harmful to our health (check out the
glycoalkaloid potato story).

>This happens especially in what you describe below as "chemical
>mutagenesis", which you call conventional breeding, but I do not.

I haven't read anything about chemical mutagenesis in your first
answer, so I will explain the principles here. In X-Ray, UV or chemical
mutagenesis numerous point or frameshift mutations are introduced in
the genome of a plant by the use of high energy photons (X-Ray,
UV-light) or  chemical agents  (e.g. ethylmethanesulfonate). I
considered these techniques CB because they were already used in
1942 (by Graunhöffer(?) ) to produce 'super'wheats. These wheats were
quickly accepted and are a normal part of everyone's diet.

>Thus it MAY very well be that a certain elevated level of a secondary
>plant product is compensated by another secondary [product], or other
>substance[s] in the plant. OFTEN also these elevated levels of
>secondary plant products occur in the parts of the plant not eaten by
>humans. (capitals by HJD)
>[..], it comes down to fieldmanagment how to limit them.

I agree with most of the above; it MAY be, but how can one be sure of
such things without testing? Furthermore: field-management is often not
capable of reducing secondary metabolites in plants

>The choice was organic versus pesticides. Now with GE a new
>possibility opens up, however one with new risks and many unknowns.

My statements weren't really about disease and resistance but about the
following points:
(1) It is often difficult to get a particular trait in crops when using
wildtype plants because of the numerous genes with unknown and
(possibly) unwanted functions cotransferred with the trait.
(2) The desired trait can have adverse effects on the health of the
consumers (and if the principles underlying the trait are not known it
can come as an unpleasant surprise).

With my examples I wanted to demonstrate that with GE one has more
knowledge of what happened in the plant than with CB (place of
insertion, cotransferred genes/parts of genes, product(s), expression
patterns etc).I believe an article (also stating the above) appeared in
'Vrij Nederland' (this weeks edition, fl 6,90 -> I haven't read it;
too expensive ;-) )


>To get a certain trait in the plant in GE  a vector is used that
>carries  the genes. This is never "just one gene", but always
>a combination of genes from different sources: viral, bacterial
>and plant or animal genes are connected together on the
>vector which is brought into the plant. [...]. One of the main
>questions still today is what the interaction of these genes on
>the vector exactly does.

The most common method to transfer DNA to dicots is the use of
Agrobacterium spp. To do this the construct is placed between the
left and right border sequences (LB/RB) of the T-plasmid. This
plasmid is then transferred to a pVir containing Agrobacterium strain.
During the co-culturing of the plant and Agrobacterium the DNA
sequence between the left and right border is transferred to the plants.
The vector DNA remains in Agrobacterium. A generalised
schematic construct looks like this:

Promoter--->selection marker-----terminator-|---/            (continued)
-/--Promoter-->gene of interest---terminator--|

The marker and desired gene can originate from almost any organism.
The promoters (from plants or plant viruses) on the contrary are highly
optimised for the plants genetic system.
Frankly, I don't see the relevance of the origin of the DNA when
considering safety.

Interactions between the (in function) unrelated genes and their
products
are possible but highly unlikely.  (What exactly do you mean with
'interaction of genes' ?) Possible interactions between the thousands
of unknown genes in CB are also unknown and since many of the
products of these genes have a related function (e.g. in the same
metabolic pathway) these interactions are more likely to occur. (It is
even harder to predict them, because of the unfamiliarity of many
transferred genes)


>To use herbicide resistance as selectionmarker  is as doubtful as to
>use antibiotic resistance.

Since there is quite a lot of pressure on the industry to get rid of the
antibiotic resistance genes I proposed the use of selection markers
that confer resistance against toxins not used as medicine or in
agriculture (e.g. obsolete herbicides or antibiotics that are toxic to
eukaryotes as well (alpha-amanitin ?))


>Then the place where the geneconstruct ends up in the plant may vary as
>you indicate. Now it's wonderful to first choose the useful clones, but
>these plants are used in the fields and conventionally bred further
>with other varieties, by which process the geneconstruct may end up in
>another place in the next plantgeneration.

In the selection process clones are selected that meet certain criteria
(number of inserts, place of the insertion, expression levels etc).
Once integrated in the genome the chance of illegitimate recombination
is approx.. equal to the chance of illegitimate recombination of normal
plant genes.


>Why should proven practices not be our guidance for the future???

Ok, you are right.
Conventional breeding is a powerful technique, but it has its
limitations. If a new technology appears you can't invalidate its
benefits by saying that 'we did it since the beginning of mankind
with CB'

>This is exactly why it says: not less safe than conventional
>counterparts.

With GE a little bit more is known about the changes in the plant than
with CB. This greatly facilitates testing etc. There is NO reason to
assume that CB created plants are generally safer than GE-created
plants.

>The testing of conventional crops has been done extensively by our
>ancestors.

Yes, but this only proves the safety of the crops; not the safety of the
technique.

>[...] much more research is welcome in the working
>of conventional plants. We should indeed get a much fuller
>understanding of the processes taking place in plants and
>their interaction with human bodies. To me on the basis what
>we know already now plants are awesome creatures and we
>should treat them with care and respect for their own
>behaviour, which is to a large extend ways beyond our comprehension.
>The more we learn about them the more modest we normally will become.

You're right, plants are marvellous biological systems.

Heine J. Deelstra
==============================
<h.j.deelstra@bioledu.rug.nl>
public key available at pgp.surfnet.nl



===================================================

The total text of the message I recieved Thursday 10/06

wytze wrote:

>
>
> Heine J. Deelstra wrote:
>
>> Anything in quotes followed by <Wytze> was written by Wytze de Lange
>>
>> "Dear mr. Deelstra,
>> I took a look at the website you mention below. I went to the
>> section:
>> genetic engineering versus conventional breeding. It contains no
>> news
>> for me, except the arguments got even worse. Before, the argument
>> was
>> that genetic engineering was better than cellfusion, where varieties
>>
>> from the same species are fused that do not mix naturally anymore. I
>>
>> agreed with the fact that cellfusion is a very doubtfull technique.
>> However, since all the risks are not known it is not possible to say
>>
>> what is worse. To argue now that GE is better than conventional
>> breeding, because it is more precise is really saying: "we are
>> better
>> than nature" or for religious people "we are better than God"."
>> <Wytze>
>>
>> Analogy: To state that cycling is a more efficient way of transport
>> than is walking in terms of energy required/covered distance isn't
>> really saying that 'We (?) are better than Nature and/or God'. The
>> technology is just better suited for our needs  than natural
>> locomotion. With needs as applied to crop breeding I mean; accuracy,
>>
>> speed and ease of 'implementation' of a particular trait. (HJD)
>
>> Wytze: I disagree with the analogy. Biking is a mechanical device
>> not changing anything about  walking. Mankind has developed many
>> mechanical devices, a lot of which are very useful indeed. Many of
>> these devices are based on naural mechanisms, so working along the
>> lines of nature. However, this is clearly not the case in GE.
>
>  "Well, if you share that position, I have a few questions to you:
> please explain me in all details all about what happens in
> conventional breeding.  I want to see your 100% understanding. I also
> would like to see the 100% understanding of what happens in GE."
> <Wytze>
>
>> 100% is a lot, but I'll try. (BTW: Do you have a 100% understanding
>> of
>> conventional breeding and cellular processes in plants? Many GE
>> activists assume (a priori) that conventional breeding is safe. But
>> why do they? Is it the deeply rooted myth that anything natural just
>>
>> because of being natural is healthier and/or better than anything
>> made
>> by man?) (HJD)
>
> Wytze: No, I absolutely do not have a 100% knowledge of conventional
> breeding, but I do not claim to make it better! As far as I understand
> things, nobody has more than a few percent knowledge of all that
> happens in plants, so it is quite contentious to claim to be better
> than conventional breeding.  Why do many people claim that
> conventional breeding is safe? This is our common history! Mankind has
> learned over the past 10.000 years or so which plants how to use in
> the ways these plants are good or at least not harmful to our health.
> Than the health effects are also affected by the way we prepare the
> plants or eatable parts thereof. The official concept is called: GRAS
> foods (Generally Regarded As Safe).
>
>> I will use pest and disease resistance as an example in the
>> following.
>> The problem in developing such resistant strains is that many
>> features
>> that render a plant resistant to pests and disease often render the
>> plant less eatable (due to extensive lignification, production of
>> phytoalexins, terpenes, alkaloids etc). I quote: "[...], the very
>> defense compounds that increase the evolutionary fitness of plants
>> by
>> warding off fungi, bacteria, and herbivores also make them
>> undesirable
>> as food for humans. Agriculturally important crop plants have been
>> artificially selected for producing relatively low levels of these
>> compounds. This, of course, makes them all the more susceptible to
>> insects and disease." (#1)
>> Transferring resistance from a wildtype (wt) plant to a cultivated
>> variety by conventional breeding may result in a surprisingly toxic
>> plant, especially if the basis of resistance was not known  (HJD).
>
> Wytze: This happens especially in what you describe below as "chemical
> mutagenesis", which you call conventional breeding, but I do not. I
> consider it the grey area of techniques between conventional breeding
> and GE. I already said in my first answer that I agree that toxic
> plants may come from that technique. The quote you give refers
> actually to two points. One is plant composition, the other is
> disease-resistancemanagement. As far as plantcomposition concerns: our
> knowledge about all the interactions in the substances of plants is
> still incredibly small. Thus it may very well be that a certain
> elevated level of a 'secondary plant product' is compensated by
> another secondary, or other substance in the plant. Often also these
> elevated levels of secondary plant products occur in the parts of the
> plant not eaten by humans. As far as these products reach levels are
> really undesired, it comes down to fieldmanagement how to limit them.
> The choice was organic versus pesticides. Now with GE  a new
> possibility opens up, however one with new risks and many unknowns.
>
>> Even if
>> the basis of resistance is known and known to be safe conventional
>> breeding can introduce transposable elements from the wildtype
>> strain
>> and unknown genes in close proximity of the 'resistance' gene will
>> be
>> very very hard to breed out (a phenomenon called linkage
>> disequillibrium).
>> With GE the resistance gene will be isolated, sequenced etc and if
>> necessary modified to suit the host. These transferred genes and
>> their
>> products are often well characterised. The only genes/ DNA-sequences
>>
>> transferred with the gene of interest are regulatory sequences and
>> selection markers (used to select transfected plants*; I think
>> leaving
>> bacterial selection markers to select e.g. A. tumefaciens is a bad
>> habit). After transfection/transformation the introduced gene will
>> recombine into a random site in the genome of a plant
>> (illegitimate/heterologous recombination). This integration can (1)
>> inactivate genes by inserting into them and (2) influence the
>> expression of other genes by inserting into regulatory sequences or
>> (3) do nothing if the DNA inserts into the large(!) part of the DNA
>> that confers no (known) function. However illegitimate recombination
>>
>> can also occur in conventional breeding techniques (not to mention
>> the
>> 'danger' of transposons). In GE, the site(s) of integration can be
>> determined by several techniques and determining the sequence around
>>
>> the site can show possible insertions into genes or regulatory
>> elements. It is than a matter of testing clones to find one with
>> satisfying expression and minimal or no side effects.  (HJD)
>>
>
You make several statements I want to comment on: To get a certain trait
in the plant in GE  a vector is used that carries  the genes. This is
never "just one gene", but alsways a combination of genes from
different sources: viral, bacterial and plant or animal genes are
connected together on the vector which is brought into the plant. To use
herbicide resistance as selectionmarker  is as doubtful as to use
antibiotic resistance.One of the main questions still today is what the
interaction of these genes on the vector exactly does.
Than the place where the geneconstruct ends up in the plant may vary as
you indicate. Now it's wonderful to first choose the useful clones, but
these plants are used in the fields and conventionally bred further with
other varieties, by which process the geneconstruct may end up in
another place in the next plantgeneration.


>>
>
>
>
>> "The webpage states something like: the genetic structure of man,
>> animals, plants and bacteria are identical. Do you know what is
>> meant
>> by that? To my knowledge this statement is either wrong or at least
>> not the full truth and certainly not the only point to take into
>> consideration and therefore wrong. I learn that genes are NOT the
>> same, they have differences." <Wytze>
>>
>> I think the page ment that (1) the chemical constitution of DNA is
>> essentially the same (A,T,G,C) and (2) all units in the genome are
>> something like promoter-code for polypeptide-terminator. The last
>> simplified scheme is extensively modified in eukaryotes but one can
>> (more or less) easily modify bacterial genes to accommodate for
>> those
>> changes. More problematic are posttranslational events like
>> cleavage,
>> glycosylation, folding and disulphide bonding. This is however a
>> larger problem when expressing eukaryotic proteins in prokaryotes
>> than
>> vice versa. Researchers of course  test for those kind of things
>> because these problems could render a protein inactive.
>>
>> "My point is: Mankind has lived since its beginning on conventional
>> breeding." <Wytze>
>>
>> IMHO: I don't think you have a point. What we did since the
>> beginning
>> of mankind should not be a guidance in our planning of today or the
>> future. Some traits are very hard to get into plants. To disable
>> pectinase in tomatoes one can wait for a mutant (can take a very
>> long
>> time) or use UV or chemical mutagenesis (=conventional breeding).
>> The
>> last method will result not only in the inactivation of the
>> pectinase
>> gene but also in countless unknown mutations in the whole genome of
>> the plant. With GE one can insert an anti-sense RNA and voila;
>> sufficiently lowered levels of pectinase. Control (e.g. tissue/time
>> specific expression) of the construct will also be more precise than
>>
>> in a UV or wildtype mutant. (HJD)
>
See my remarks before on chemical mutagenesis. The anti-sense technique
is far less good than supposed, besides it may exactly also have very
unwanted side-effects. Also it still needs bacterial and viral genes,
which is very much questioned.  Why should proven practices not be our
guidance for the future???

>>
>>
>> "Official policy is that GE foods should be not less safe than
>> conventional food, that's something else than  "the benefits
>> outweigh
>> the risks" as the website does. Whose benefits?? Whose risks?? Do
>> you
>> know?" <Wytze>
>>
>> Saying that food or anything else is safe is an oversimplification
>> of
>> the world around us. Nothing is absolutely safe; nor GE, nor
>> conventional breeding nor breathing or whatsoever. (HJD)
>
Wytze: This is exactly why it says: not less safe than conventional
counterparts.

>> If safe is such a major issue  I myself would plee for a case by
>> case
>> testing of new crops (GE or conventional)
>> (BTW have you ever read a thorough test of broccoli? Yet it was
>> quickly accepted by consumers!)
>>
>
The testing of conventional crops has been done extensively by our
ancestors. I do agree that much more research is welcome in the working
of conventional plants. We should indeed get a much fuller understanding
of the processes taking place in plants and their interaction with human
bodies. To me on the basis what we know already now plants are awesome
creatures and we should treat them with care and respect for their own
behaviour, which is to a large extend ways beyond our comprehension. The
more we learn about them the more modest we normally will become.wytze

>> References:
>> (#1) L. Taiz & E Zeiger. Plant Physiology. p321 'Secondary Plant
>> Products'. The Benjamin/Cummings Publishing Company, Inc.
>>
>> * an alternative selection marker would be a gene that conferred
>> resistance to herbicides (e.g. glyfosfate resistant EPSP synthase)