Conrad Paul Lichtenstein
Times ; 01-Apr-2000
The technology behind genetic modification of crops is
not inherently dangerous, nor fundamentally different from events in
nature or classical plant breeding in agriculture.
It began in the strawberry fields. In the early days of genetic
modification of crops. Californians were among the first to revolt.
Some of them attacked a field trial of strawberries in the early 1980s.
It was not the strawberries that were modified, how ever, but certain
bacteria on the surface of the strawberries that encouraged frost
damage by allowing water to freeze more easily. The frost-damage gene
in the bacteria was deleted and the strawberries were then coated to
see if this protected them from frost damage. Europeans looked on
bemused at what seemed a hysterical overreaction, the bacteria, after
all, did not carry a new foreign gene but had merely had an existing
gene removed. How could this be dangerous?
Years later, the world was caught unprepared by a sudden invasion into
the marketplace of modified crops. Last year, an estimated 70 per cent
of the soya grown in the US was GM, with the
00FF,0000,0000other main GM crops being
cotton and maize.
Two foreign bacterial genes have been introduced: one giving herbicide
resistance so allowing better weed control by permitting herbicide
application after sowing the crop and the
00FF,0000,0000other insect pest control.
No longer bemused, this time Europeans led the revolt.
The GM debate is complex, with several intertwined questions. Is the
consumption of GM food hazardous to human health? Will GM crops harm
innocent organisms by entering the food chain? Is the escape of foreign
genes into wild species genetic pollution that will alter genetic
diversity and upset ecosystems? Are too few companies controlling food
production, exploiting poor farmers with expensive protected seed and
plundering genes from the third world?
Greenpeace and 00FF,0000,0000other
environmental protection groups launched this debate by preying on the
fears among the scientifically ignorant of what they see as an alien
and unnatural technology. Yet GM is not unnatural. Indeed, those of us
who still smoke inhale the combustion products of a natural GM event
where foreign DNA entered tobacco millions of years ago somewhere in
the Andes. Genes are handed on from parents to their offspring by
"vertical transmission". As the hereditary genetic information
replicates, natural errors - "mutations" - occur at random, generating
The cumulative natural selection for the more successful variants among
these offspring drives change, leading to the formation of new species.
This is evolution as Charles Darwin presented it but with the added
spice of genes from Gregor Mendel, the father of modern genetics, and
our modern understanding of both DNA as the physical embodiment of this
genetic information and of how mutations occur.
Language also changes during vertical transmission over human
generations, for example from Chaucer's to Shakespeare's to modern
English. But just as English has acquired and assimilated foreign words
naturally, organisms call also acquire foreign genes naturally from
00FF,0000,0000other species through
Horizontal transmission can also occur on a grander scale than the
transfer of a few words or genes: the English language, which followed
the Norman invasion in 1066, became a hybrid with the lexicon of two
languages as it assimilated Norman French, becoming quite distinct from
the more Germanic Old English. Grand "Norman invasions" are frequent
events among plants: perhaps one third of living plant species evolved
from natural hybrids. Unlike animal hybrids such as mules (a cross
between a horse and a donkey), plant hybrids are not necessarily
Plant breeders have exploited this. For example, modern wheat carries
large stretches of DNA from rye, another cereal not by using GM
technology, but by classical plant breeding early last century. So the
outcome is similar to modern genetic modification even if the
technology is different.
Even grander invasions took place in nature 1.5bn years ago when one
cell "swallowed" another. The swallowed cell retained a separate
identity and evolved into the organelles mitochondria that provide
energy to the cell, and chloroplasts for photosynthesis in plants.
Genome sequencing projects going back even earlier in time are
revealing that our picture of the tree of life is becoming distorted by
increasing evidence of rampant horizontal gene transfer, even between
bacterial and animal and plant kingdoms.
In language, not all words are acquired naturally, some are invented by
mining the classics - Attic Greek and Latin - and recombining their
roots. Examples include technical words such as "graphemes", the
written symbols on this page that encode the spoken "phonemes" if read
out aloud. With use, many such "recombinant graphemes" such as
"telephone" or "television" feel comfortable and almost natural.
GM crops that carry the genes of
00FF,0000,0000other organisms are
similarly a result of artificial horizontal transmission of recombinant
genes. In a model study, my university laboratory made virus-resistant
GM tobacco plants by altering the plant's DNA to prevent invading
viruses from producing a replication protein.
The experiment worked: the GM plants prevented the invaders from
producing more copies. But then we found (now silent) DNA sequences
similar to the very ones we were putting in artificially.
Our results suggest that about 5m years ago, an aphid bit a plant and
transmitted the virus. The resulting GM plant cell must have given rise
to cells that developed into a flower that produced seeds carrying this
new DNA. These seeds germinated and new plants arose.
Either by chance, or perhaps by virtue of a new advantage, plants
carrying these new genes came to pre-dominate in the population so that
eventually all members of this species came to carry them. This plant
species was the ancient ancestor that evolved into the four distinct
species that carry these sequences today. Recently,
00FF,0000,0000other viruses have also
been discovered lurking in the genomes of the banana and tobacco
species, suggesting that, in plants, this type of horizontal gene
transfer may be more common than we thought. There are
00FF,0000,0000other examples of
horizontal gene transfer to plants. Certain soil-living bacteria are
natural genetic engineers which infect wounded plants and transfer DNA
to plant cells, leading to a benign tumour known as crown gall disease.
It is typically only a portion of the plant that carries this bacterial
Some time in evolution, however, such crown gall tissue must have
become transmitted through seeds to an early progenitor of tobacco and
related species that all carry such sequences. But is horizontal gene
transfer to plants more widespread in nature? Recent studies reveal a
vast wave of horizontal transfers rather recently in evolution from
fungi to the mitochondria of plants.
Among bacteria, natural horizontal gene transfer happens frequently.
Soil bacteria produces antibiotics for waging chemical warfare on their
competitors. For aeons, naturally occurring antibiotic resistance
genes, which equip these bacteria with antidotes against their two
toxins, must have transferred naturally between bacteria. The
excessive use of antibiotics to combat infectious disease in humans and
in a food additive to boost growth in livestock has resulted in new
bacterial pathogens with multiple drug resistance. It seems it is not
the lack of opportunity for horizontal transfer that governs the
frequency with which it occurs in nature, but whether the new "genetic
graft" offers any advantage in the fierce arena of natural selection.
Back in the world of language, Esperanto, invented about 100 years ago,
is a delicate, sensitive and artificial creature that has failed to
take root. In contrast, overcoming much resistance from language
purists, new words enter a language in response to the powerful
selective pressure of popular culture. Despite the opposition of the
French Academy, English words such as "weekend" and "snack bar" have
long been in the French lexicon. What can this teach us about genetic
pollution? Can cultivated crops cross with wild relatives? When such
crops are growing where wild relatives are endemic, this is certain to
happen, and difficult to contain - for example, in Europe between GM
oilseed rape (canola) and wild relatives.
But such escapes are not unique to GM crops. Cultivated crop plants, by
virtue of selective breeding and hybrids, are already genetically
different from their wild relatives. Thus genetic pollution in the form
of the movement of genes from cultivated crop plants to wild relatives
has also occurred since agriculture began.
However, cultivated crops do not have the resilient characteristics of
wild plants that allow them to compete in the struggle for survival
outside the field. Cultivated crops are weaklings that suffer the fate
Will herbicide resistance genes escape from GM crops to produce
superweeds? Wild relatives that acquire these genes will survive
herbicide treatment and reproduce to increase their number. Thus the
herbicide will become rapidly and progressively less effective and so
will have to be replaced by a different one. Plants outside the field
and not subjected to herbicide treatment would gain no such advantage
by acquiring these escaped genes, however. It is thus difficult to
imagine how they could disturb the natural ecosystem. Spontaneous
resistance to herbicides in weeds and crops can in fact occur simply by
the natural selection of random mutations following repeated
applications of single herbicides: this has been known for 50 years.
Yet there have been no adverse ecological effects.
There are 6,000 languages spoken in the world today yet many face
extinction, with perhaps only 3,000 surviving through this century. The
threat comes largely from the invading leading world languages by
cultural assimilation. Alien plants introduced by gardeners to
woodlands, for example the rhododendron, are similarly a serious threat
to indigenous plant species and can bring about large changes in
biodiversity in natural ecosystems.
Once again these invaders spread not because they are alien, but only
if they have a competitive advantage acquired in their native habitat
as a consequence of natural selection. These aliens can also hybridise
with indigenous species. This is genetic pollution, not of the odd
gene, but on a genomic scale, yet it has nothing to do with GM crops.
Thus GM technology is not inherently dangerous, nor fundamentally
different from events in nature or classical plant breeding in
agriculture. We should not be eclectic in what we choose to fear and
should appraise this new technology rationally and in an informed way
and also see it in the context of the more serious threats to
ecosystems from industrial activity and from crops awash with
herbicides, pesticides and 00FF,0000,0000other
Although not intrinsically more dangerous than the products of
intensive agriculture it would be foolish to assert that all GM is
inherently safe, however. GM food should be subject to the same
scrutiny as all novel foods and GM food should be clearly labelled to
give consumers choice, just as they have for organic food.
Whether globalisation and company mergers present a threat to open
competition in the market extends beyond the domain of GM crops; and it
is not even an issue restricted to agribusiness. However governments
are able to regulate monopolies amid prevent unfair exploitation.
The present public mood is anti-science, and retreating into mysticism
and superstition. People lack a basic understanding of science,
especially biology. Society changes, culture changes, language changes,
species change, yet we are sentimental romantics and lament change.
#The author is professor of molecular biology at Queen Mary and
Westfield College, University of London.
Copyright © The Financial Times Limited