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The findings of a risk assessment study emphasise
the effectiveness of case-by-case evaluation of GM plants and the
important role science can play in decision-making around the
introduction of GM crops.
Print this pdf fact sheet (180KB).
The importance of peas
Field peas are an important rotation crop for Australian farmers.
Worth 100 million dollars a year, they add nitrogen to the soil and
reduce root disease among following crops.
But field peas are susceptible to the pea weevil Bruchus pisorum,
which lays its eggs on the pea pod. When the eggs hatch, the larvae
eat their way through the pod and into the seed, where they develop
into adults, leaving a large hole when they emerge from the pea.
Weevils can reduce yields by up to 30 per cent and any sign of
weevil damage will cause the peas to be downgraded in quality and
reduced in value. Weevil damage also reduces the viability of seeds
for the following season. Crops must be hand-checked for infestation
every three to four days from the start of flowering if pesticides are
to be applied in time to prevent infestation.
Alpha-amylase inhibitor GM peas
CSIRO developed genetically modified field peas using a gene from
beans.
Unlike peas, beans are not attacked by pea weevils. Beans contain a
protein that inhibits the activity of alpha-amylase, an enzyme that
helps in digestion of starch. This protein inhibitor, called
alpha-amylase inhibitor, causes the weevils feeding on beans to starve
before they cause any damage.
CSIRO scientists and their collaborators identified the gene that
produces the protective protein. Using gene technology they then
introduced the gene into the pea. Field trials showed the genetically
modified peas were 99.5 per cent resistant to pea weevils.
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The CSIRO-developed GM field peas (right) provided 99.5 per cent
protection against the pea weevil
Bruchus pisorum.
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Risk assessment
CSIRO's GM field peas underwent a number of tests during
development:
1. Laboratory and glasshouse tests
2. Performance studies in the field
3. Gene flow studies
4. Feeding trials
5. Immune response tests
Results of trials 1 - 4 are already published or submitted for
publication.
Immune response study
The bean alpha-amylase inhibitor protein has been studied
extensively over many years and has shown no health risk to humans or
animals. However as part of its risk assessment, CSIRO asked the John
Curtin School of Medical Research in Canberra (JCSMR) to help examine
whether the pea form of the alpha-amylase inhibitor protein caused an
immune reaction in mice.
Mice were fed either beans, non-GM peas or alpha-amylase inhibitor
GM peas twice a week for four weeks. In a separate experiment, the
reaction to the pea alpha-amylase inhibitor protein was compared to
bean alpha-amylase inhibitor protein when administered to the mice
lungs.
Mice fed beans did not show evidence of an immune reaction.
Similarly, mice fed non-GM peas did not demonstrate any immune
reaction.
Mice exposed to alpha-amylase inhibitor GM-peas showed evidence of
an immune response after two weeks, with the response increasing at
four weeks. The reaction in mice was evident by inflammation in the
lungs and increased serum antibody levels. The research also showed
that after eating the GM peas, there was evidence that the pea
alpha-amylase inhibitor protein primed the mice to react to other food
antigens.
Why a response to alpha-amylase inhibitor GM peas?
To understand why the mice reacted to the GM pea alpha-amylase
inhibitor, the CSIRO team analysed and compared the molecular
structure of the bean and pea alpha-amylase inhibitor proteins.
This revealed small mass differences in the two proteins, most
likely to be caused by different protein processing steps in two types
of cell, including one step called glycosylation.
These processing steps play an important role in making certain
proteins, and can lead to variation in a protein's structure. This
research shows however, that these variations can have other effects
supporting the need for case-by-case assessment of GM crops.
Other assessment
Six performance trials were conducted under field conditions
between 1996 and 2001. Results showed the alpha-amylase inhibitor GM
peas provided 99.5 per cent protection against the pea weevil with
yields comparable to non-GM field peas.
Peas are self pollinating and it is unlikely gene flow would occur
between GM and non-GM peas. However CSIRO conducted gene flow studies
to test this assumption. The results of the work showed that gene flow
did not occur between GM and non-GM field peas.
CSIRO also examined scientific literature to determine what
wildlife and in particular birds relied on field peas in their diet.
It found little evidence of wildlife eating field peas and provided
information for consideration by the former Genetic Manipulation
Advisory Committee now the Office of the Gene Technology Regulator (OGTR).
The technology
The technology developed by CSIRO to genetically modify field peas
with novel genes is a gene transfer system for peas.
The system is now available for use in other research including
exploring the potential to develop protection against agronomically
important diseases of pea.
Outcomes
Given the findings of this research, CSIRO has made the decision to
discontinue work on the alpha-amylase inhibitor GM peas and is
finalising arrangements with the OGTR for the disposal of GM field
peas produced during the project.
References
Transgenic Expression of Bean α-Amylase Inhibitor in Peas Results
in Altered Structure and Immunogenicity
Vanessa E. Prescott, Peter M. Campbell, Andrew Moore, Joerg Mattes,
Marc E. Rothenberg, Paul S. Foster, T. J. V. Higgins, and Simon P.
Hogan.
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 53, Issue 23 (November 16, 2005) pages 9023 - 9030
Links
CSIRO's
position on gene technology
Print this pdf fact sheet (180KB).
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