Transcript Risk Assessment of GM Plants

Risk Assessment of GM Plants
Assoc. Prof. Dr. Wichai Cherdshewasart
Department of Biology, Faculty of Science,
Chulalongkorn University
Tel 02-2185033 Fax 02-2185034
Modes of plant gene modification
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Classical breeding (wild crossing)
Mutation
Somaclonal variation
Protoplast fusion
Embryo rescue
Gene transfer
1. Classical breeding (wild crossing)
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Advantage:
practical, low cost, stable, effective
within species
Disadvantage:
time-consumed, ineffective within
different species
2. Mutation
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Advantage:
practical, low cost
Disadvantage:
randomized, needs long selection
procedure, not totally stable, may
initiate revertant
3. Somaclonal variation
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Advantage:
in vitro manipulation
Disadvantage:
takes time, randomized, needs long
selection procedure
4. Protoplast fusion
Advantage:
across species barrier
 Disadvantage:
randomized, remote species may
success but fail for further
development
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5. Embryo rescue
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Advantage:
cross between different species is
possible to initiate embryonic
development.
Disadvantage:
transfer pre-mature embryo to new
environment could initiate fully
developed plants, but sterile
6. Gene transfer
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Advantage:
precise genotype obtained,
laboratory and industry practical
Disadvantage:
Not possible for all species,
especially monocot
Mode of gene transfer:
1. Vector-mediated gene transfer
 Agrobacterium-mediated
 Virus-mediated
2. Vectorless-mediated gene transfer (Direct gene
transfer)
 Mechanical
 Physical
 Electrical
 Chemical
Analysis of transgenic plants
1. Phenotypic analysis
2. Genotypic analysis
3. Greenhouse condition analysis
4. Field trial condition analysis
Genotypic analysis
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PCR for rapid screening
Southern blot for precise gene detection
Northern blot for transcription analysis
Western blot for translation analysis, together
with Ab-binding or enzymatic analysis
Mendelian analysis for insertion locus and
linkage analysis
In situ hybridization for precise insertion
locus analysis
DNA methylation analysis for silencing
potential analysis
A generally accepted risk assessment
method*,**,***
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Identify potential adverse effects on human health
and/or the environment
Estimate the likelihood of these adverse effects being
realized
Evaluate the consequence should be identified effects
be realized (the risk)
Consider appropriate risk-management strategies
Estimate the overall potential impact, including a
consideration of potential impacts that may be
beneficial to human health or the environment
*
UNEP International Technical Guideline for Safety in Biotechnology
** The Cartegena Protocol
*** EC Directive 2001/18/EEC
Approaches to risk assessment
1. Trait analysis
 characteristics of the modified organism; transgene,
parental organisms, receiving environment
 less problem, if small scale
 more problem, if large scale
2. Familarity
 comparison of transgenic to similar organism(s) derived
from classical genetic methods
 assume that small genetic changes (1-4 genes) exhibits no
significant change in well-known organism, phenotype is
still the same
3. Formulaic
 possible adverse effects; to human health or the
environment
 R = H x E
 R; Risk, H; Hazard, E; Exposure
 facilitates consideration of risk-management
options
4. Intuitive Reasoning
 use education, experience and reason to promote
knowledge for making decision with complete
information
 depends on what should be considered
 use of expert committees, independent
reviewers/assessors without a conflict of interest
Environment Safety Assessment
For Transgenic Crops:
Needs:
1. Environmental friendly products
2. Tight global regulatory requirements
3. Trade barrier
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Methods:
1. Product and country specification
2. Science-based assessment
3. Multi-tiered, complementary approaches
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Plant assessment:
1. Survival against wild type plants
2. Stability of gene expression, especially in
the field vs. laboratory / greenhouse
3. Distinct genotype over wild type plant
4. Invasiveness of transgenic plants, the
possibility to develop into weeds
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Trait assessment:
1. Toxicity to non-target organisms
2. In case of human consumption,
no allergen / toxic substance
3. Ecological impacts (outcrossing)
Guidelines for Plant Testing
1. Field obseravation
Emergence
Order of testing relies on degree of
possible risk of the plant
Growth
Transgenic plant growth / wild type,
not greater than 1
measurement
Days of flowering Transgenic plant days of flowering /
wild type, not greater than 1
Length of
flowering period
Transgenic plant length of flowering
period / wild type, not greater than 1
Pollen dispersal
distance
This is the reason why buffer zone
has to be set up)
Shattering of seed
from plant
Reproductive success
or yield (annual)
Distance of seed shattering
determines degree of risk
Reproductive success
determines transmission risk
Reproductive success Perennial risk determines more
risk
or yield (perennial)
Qualitative insect
Non-target insects = 0
Qualitative
pathogens
Others
Non-target pathogens = 0
2. Plant testing
Dormacy/ germination
-shorter dormancy / germination
determine front running risk
-longer dormancy / germination
determine latent risk
risk
-increase longevity determines risk
Field seedbank longevity
(dormancy x viability)
Competition
(Replacement or
addition series)
-stronger competition determines risk
Replacement capacity
-higher replacement capacity
determines risk
Gene flow (through -wider pollen dispersal determines risk
pollen movement) -outcrossing determines risk
Introgression
(hybrid weediness)
-hybrid weediness determines long term
risk
Alleopathy
-Competitive of survival risk
Susceptibility to
conventional
management
Genetic stability
-Competitive of agricultural risk
Epistasis
-Epistasis determines unexpected genetics
-Horizontal gene transfer
 Gene transfer between plant nucleus and
organelle
 Gene transfer between plant nucleus and
genome of consumer, predator, Gene
transfer between nucleus and organelle
Other
-High genetic stability determines risk
Regulatory principles:
1. Scientifically based, based on information of organism,
used technology and effects to humans and environment
2. Product-based approach, use existing product-based
legislation
3. Familiarity and substantial equivalence, experience with the
use of that species. The determination is based on scientific
literature and practical experience with the plant and
similar plant varieties.
4. Case-by case, allow the development of knowledge that
could inform criteria and requirement over time.
Regulatory principles:
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Step-wise fashion, products should be assessed throughout
the chain of development : From laboratory to greenhouse
and finally large-scale field trial
Transparency
Precautionary principle/approach, derived from Rio
Declaration, regulatory groups can make decisions about
products based on scientific uncertainty.
Harmonization, sharing of or acceptance of another group’s
review
1. Good laboratory practice
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Tightly control of GM-vectors, plasmids and plant
materials
Apply no bacterial antibiotic resistant-derived gene
Apply bioluminescence gene from animal as
marker
Apply antisense for pollen developmental gene
Limit level of toxic gene, eg, cry family
2. Good agricultural practice
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Controlled plantation area with standard buffer
zone and % sharing with wild type plants
Emasculation
Flower bud elimination
Closed-bag control
Net protection of fruits and seeds from insects,
birds, bats, rodents
Total fruit and seed collection
Labeling and separation technique for transgenic
plant and seed
Whole plant elimination after harvest
3. Good manufacturing practice
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Labeling GM-products according to domestic and
export regulations
Testing for allergen and toxicity of the products
containing GM-materials
4. Good marketing practice
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Fully-informed alien gene(s) and awareness of
application
Evaluated for allergen and toxic molecule
Labeling
Post marketing record
5. Good consumption practice
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For GM-food products: determine animals as
primary consumer and human as secondary
consumer
Study labeling
Food safety criteria
References
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Head G. and Duan J. 2002. Environmental safety assessment for
transgenic crops.
Wolf K. 1994. Gene transfer between organelles and the nucleus in lower
eukaryotes
Copy P. Bazin C. Anxolabehere D. Langin T. 1994. Horizontal transfer and
the evolution of transposable elements
Landmann J. Graser E. Riedel-Preuss A. van der Hoeven C. 1994. Can
Agrobacteria be eliminated from transgenic plants?
Hoffmann T. Golz C. Schieder O. 1994. Preliminary findings of DNA
transfer from transgenic plants to a wild-type strain of Aspergillus niger
Hansen L. C. Obryeki J.-J. L. 2000 Field deposition of Bt transgenic corn
pollen: lethal effects on the monarch butterfly.