2-Plants: GE canola genotype can be modified by pathogen invasion
- To: GENETemail@example.com
- Subject: 2-Plants: GE canola genotype can be modified by pathogen invasion
- From: GENETNL <firstname.lastname@example.org>
- Date: Tue, 5 Sep 2000 09:44:19 +0200
- Content-Transfer-Encoding: 7bit
- Content-Type: text/plain; charset="us-ascii"
- Reply-To: email@example.com
- Sender: firstname.lastname@example.org
genet-news mailing list
----------------------------- GENET-news -----------------------------
TITLE: A) Comment of Natural Law Party Wessex
B) Plants rendered herbicide-susceptible by cauliflower
mosaic virus-elicited suppression of a 35S promoter-
SOURCE: A) NLP Wessex, UK, email@example.com
B) Nature Biotechnology, Vol. 18 (9), pp. 995 - 999
by Al-Kaff et al.
DATE: A) August 31, 2000
B) September 2000
-------------------- archive: http://www.gene.ch/ --------------------
The scientific abstract (below) just released in the September 2000
edition of scientific journal 'Nature Biotechnology' is going to
cause some interesting discussion.
What this study found is that oilseed rape genetically modified to be
resistant to a herbicide lost that resistance when it encountered a
naturally occurring environmental pathogen (the Cauliflower Mosaic
Virus). In other words had the farmer sprayed this rape in the field
with the recommended herbicide the oilseed rape would have been
killed as well as the weeds - not quite the idea of this technology!
This could lead to some interesting crop loss claims by farmers
against biotech companies if it happened on a large enough scale in
The Cauliflower Mosaic Virus (CaMV) is a common pathogen of brassicas
(cabbage, caulifower, rape etc). In this case genetically modified
rape which became infected by it (a common occurrence with brassica
crops) lost its resistance to the herbicide. The relevant gene
conferring herbicide resistance appears to have become switched off.
The herbicide in this case is bialaphos.
Such 'gene silencing' has previously been considered to result from
an interaction between the invading environmental pathogen and the
viral 'promoter' (itself taken from the CaMV) which is used to
artificially fire up the foreign transgene in the first place. This
particular viral promoter is used in most transgenic crops, into
whose every cell it is embedded.
This study is particularly interesting as it concerns the bialaphos
herbicide which is related to glufosinate-ammonium, the herbicide to
which most of the crops in GM fieldscale trials in the UK have been
developed by Aventis to have resistance. It would appear that the
same transgene provides resistance to glufosinate-ammonium as to
bialaphos (see footnote). How comfortable would most UK farmers feel
about this if they knew about it (or for that matter Aventis's
shareholders and insurers)?
The use of the CaMV 35s promoter in most transgenic crops is one of
the most controversial technical aspects of the use of GM in
agriculture. The risks associated with it go well beyond the 'gene
silencing' apparently demonstrated in this case. For more information
on those risks see: www.btinternet.com/~nlpwessex/Documents/camv.htm
This particular paper abstract from Nature Biotechnology finishes
with the words: "Our results show that transgene phenotypes can be
modified by pathogen invasion".
In other words the characteristics of genetically modified crops may
change when they are released into the environment and interact with
naturally occurring pathogens such as viruses. It is interesting that
this should be reported in the scientific literature literally years
after the large scale introduction of these types of crop into the
environment around the world, particularly when such introduction has
been based on insistence from scientists and regulators that they
know what they are doing and everything has been fully tested. Draw
your own conclusions!
This latest paper on the subject was produced by scientists at the
John Innes Centre which is an advisor to the UK government on safety
aspects of GM crops. The JIC previously commented on such gene-
silencing phenomena in a paper published in 1998 as follows:
".....Recent research in our laboratory with Brassica napus plants
containing the 35S promoter from the mosaic virus (CaMV) has shown
that upon infection with the CaMV the driven transgene is silenced
(Al-Kaff et al unpublished). Intensive research at present is
directed towards understanding this silencing mechanism and its
As the 35S promoter is widely used to regulate transgenics in
brassicas, it is important that we strive to obtain a clear
understanding of the mechanisms of this silencing and its
significance. This is important for two reasons, for assessing the
use of the 35S promoter in agriculture and also for assessing the
significance of this effect for biosafety. The presence of homology
between the 35S promoter and the infecting virus is clearly important
in determining this silencing phenomenon ....
A knowledge of transgene stability, expression and inheritance is
fundamental for the successful and safe use of transgenes in large
scale agricultural production. Many factors influence the ways in
which transgenes express, but a factor of crucial importance is the
effect of DNA sequences that are homologous to areas of transgene
constructs. For those concerned with the development of transgenic
brassicas the take home message from this paper is 'watch out for
homology' ". [emphasis added]
As the JIC commented in a further paper in 1998:
"One of the most challenging issues associated with assessing the
environmental impact of transgenic plants when in widespread
commercial production are scale dependent effects. It is possible
that a rare event may have insignificant consequences when transgenic
crops are grown on a small experimental scale, but become more
important when transgenic crops are grown over thousands of
Meanwhile this material continues to be released into the UK
environment in the form of the UK fieldscale trials and commercial
crops in other parts of the world.
NATURAL LAW PARTY WESSEX
*Bialaphos [L-2-amino-4-((hydroxy)methyl) (phosphinoyl)-butyryl-L-
alanyl-L-alanine] is a commercially available natural phytotoxin.
acid] is the synthetic version of bialaphos' herbicidal moiety,
It appears that the same transgene provides resistance to glufosinate-
ammonium as to bialaphos: http://www.stanford.edu/~walbot/
Plants rendered herbicide-susceptible by cauliflower mosaic virus-
elicited suppression of a 35S promoter-regulated transgene
Nadia S. Al-Kaff, Maria M. Kreike, Simon N. Covey, Robert Pitcher,
Anthony M. Page & Philip J. Dale
John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK.
Correspondence should be addressed to N S Al-Kaff. e-mail:
Crop plants genetically modified for herbicide tolerance were some of
the first to be released into the environment. Frequently, the
cauliflower mosaic virus (CaMV) 35S promoter is used to drive
expression of the herbicide tolerance transgene. We analyzed the
response to CaMV infection of a transgenic oilseed rape line
containing the bialaphos tolerance gene (BAR) from Streptomyces
hygroscopicus, regulated by the 35S promoter.
Oilseed rape is susceptible to CaMV, but plants recover from
infection. CaMV infection altered the expression of the herbicide
tolerance gene such that plants became susceptible to the herbicide.
The effect on transgene expression differed in infections with viral
pathogenic variants typical of those found in natural situations
worldwide. Susceptibility to the herbicide was most likely a result
of transcriptional gene silencing of the transgene. Our results show
that transgene phenotypes can be modified by pathogen invasion.
| GENET |
| European NGO Network on Genetic Engineering |
| Hartmut MEYER (Mr) |
| Kleine Wiese 6 |
| D - 38116 Braunschweig |
| Germany |
| phone: +49-531-5168746 |
| fax: +49-531-5168747 |
| email: firstname.lastname@example.org |