Download Possible risks of GMO-s

Possible risks of GMO-s
• Creating new, and more vigorous pests and
pathogens
• Exacerbating the effects of existing pests through
hybridisation with related transgenic organisms
• Harm to non-target species
• Disruption of biotic communities, including agroecosystems
• Irreparable loss or changes in species diversity or
genetic diversity
Therefore some GMO-s require greater scrutiny than
organisms produced by traditional techniques of
breeding (ESA Report, Snow et al., 2005, Ecol.
Appl., 15, 377-404.)
GMO-s posing some risks to
the environment
• Little or no prior experience with the trait and
host combination
• GMO-s may proliferate and persist without
human intervention
• Genetic exchange possible between a
transformed organism and non-domesticated
organisms
• Trait confers an advantage to the GMO over
native species in a given environment
(ESA Report, Snow et al., 2005, Ecol. Appl., 15,
377-404.)
Guidelines for GMO creation and
release
• Early planning and design of GMO-s to reduce
environmental risks (reduce risks of sterility, lower
fitness,
• The promoter should be inducible rather than
constitutive
• Selection markers should be removed before
cultivation
• Prevent large-scale or commercial releases if scientific
knowledge exist about possible risks
• Post-release monitoring to detect environmental risks
• Thorough risk-assesment, expertsts should have
multidisciplinary training
TRANSGENES
• Create organisms with traits that cannot be obtained
through normal sexual reproduction
• Novel, synthetic genes that have never existed in
nature
• Minimally they are composed of a gene sequence
flanked by a promoter and other elements that may
come from different organisms
• Phenotypic characteristics, such as size, health,
reproductive capacity are determined by complex
interaction among its genes and its surroundings, and
cannot be characterized in small-scale experiments
(ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377404.)
Herbicid-tolerant crops
(ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefits
Caveats
• Facilitate no-tillage/lowtillage weed management
– Conserves topsoil and
soil moisture, reduce
erosion
– Allows greater carbon
sequestration in soil
organic matter
• Glyphosate breaks down
more quickly and is more
„environmentally friendly”
than many other herbicides
• Glyphosate is the most widely
used herbicide in the US
• Its use may not be sustainable
if weeds shifts occur to favor
glyphosate-tolerant weeds or
weeds develop tolerance to
glyphosate
• New alternatives to glyphosatetolerant crops may be too
expensive or difficult for
chemical companies to develop
and commercialize
Bt-transgenic plants
ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefit
Caveats
• Can reduce the use of
broad-spectrum
insecticides
• May not be suistainable if
secondary pests become
more problematic and/or if
target pests evolve
resistance to the Bt crop
• Above ground, broadspectrum insecticides are
not applied to most of the
US corn acreage
• Higher lignine content
(Saxena and Stocky, 2001)
GM crop-plants with
transgenic resistance to
common diseases
ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefit
• Could reduce the use of
fungicides and
insecticides that
currently are used to
kill disease-vectors, or
disease-causing
organisms
Caveats
• May noy be suistainable if
pathogens evolve
resistance to transgenic
varieties
• Few crops with transgenic
disease resistance have
been deregulated to date
(exceptions include virusresistant squash, papaya
and potatoes)
GM crop-plants with higher yields
due to one or more transgenic traits
ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefit
Caveats
• Higher yield per acra
could reduce pressure
on natural areas
because less area needs
to be cultivated for a
given amount of yield
• Higher yield per area
could be an incentive to
cultivate transgenic crops
on larges areas
• Evidence for yield gains
above current production
levels are not well
documented as yet
Mediation of polluted soil using
transgenic plants or bacteria
ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefit
Caveat
• More effective and less
expensive clean-up of
toxic vaste sites than
with current methods
• Early in development, not
known if effective in the
field or economically
viable
Decreased lignin production in
transgenic, commertial tree
plantations
ESA Report, Snow et al., 2005, Ecol. Appl., 15, 377-404.)
Benefit
• Leaner paper milling
and less pollution of
waterways
Caveat
• Early in development, not
known if commercially
viable
Transformation of plant cells
• Using a disease causing pathogen, Agrobacterium
tumefaciensis (for dicotyledonous plants)
• Particle bombardement ( mostly for monocots)
• Physical methods
• Chemical methods
The transformation process is very inefficient (Birch,
1997)
Transgene is linked to a selectable marker, encoding
herbicid-resistance
antibiotic-resistance
UNINTENDED PHENOTYPES
• Position effects
– Random chromosomal locations, often at multiple sites
– DNA sequences may interrupt native genes, or promoter
sequences that regulate them
– Can bring about small-scale rearrangements of the transgene
and native DNA sequences at the insertion site (Pawlowski
and Somers, 1998, Svitasev et al, 2000, 2002, Windels et al,
2001)
• Interaction among the transgene and native genes
(Hartman et al, 2001)
• Pleiotropic effects of transgenes - small, unintended
effects may remain undecetcted, they may depend on
cumulative action,
environmental conditions
Introgression into different genetic backgrounds
Virus-resistant crops
• Beachy et al. (1990) discovered the general principle,
that the coat protein of a virus could provide
resistance to the same virus
• Potential ecological risks of virus-resistant crops:
• Benefit of transgenic virus over wild type
• Recombination between viral transgenes and
invading viruses (Power 2002, Tepfer 2002
• Interaction between an invading virus and the viral
RNA encoded by transgenes (Miller et al, 1997, Aziz
and Tepfer 2002, Power 2002, Hammond et al, 1999)
Virus-resistant crops
• Hazards of virus – transgene recombination
– increased virulence
– alterations to host range
– change of transmission characteristics (Schoelz and
Wintermantel 1993, Kiraly et al. 1998, Borja et al. 1999,
de Zoeten, 1991, Miller et al 1997)
• Transcapsidation (encapsidation of viral RNA of one
virus by the coat protein of another virus in mixed
infections (Power 2002, Tepfer 2002), even if at low
rates (Thomas et al, 1998, Fuchs et al, 1999)
• Synergistic interaction between viruses in mixed
infections (Miller et al, 1997)
HORIZONTAL GENE-FLOW
• 1-20% of an organism derives from foreign
DNA (Ochman et al, 2000, Koonin etal, 2001)
• Major source of microbial evolution
• Depends on population density
• Less frequent between distantly related taxa
• Most likely to occur, and had been detected in
microbial communities (Gebhart and Smalla,
1998, Nielsen et al, 1998, Bertolla and Simonet
1999, Kay et al, 2002)
Gene flow
• Transgenes are inherited and have the
potencial to disperse (Quist and Chapella,
2001, 2002, Beckie et al, 2003)
– Crop to crop
– Crop to wild (Ellstrand et al. 1999, 2003, and
Messeguer, 2003)
Fitness transgenes conferring resistance has an
effect on plant population dynamics (Power,
2002, Mitchell and Power 2003, Callaway et
al. 2004, Snow et al. 2003)