Risk assessment of GM field peas

In 2005, CSIRO reported it had discontinued research into genetically modified (GM) field peas because the peas did not satisfy all the requirements of their risk assessment process. The findings from the study highlighted the importance of a careful case-by-case evaluation of GM crops, and the role science can play in decision-making related to the development of GM crops.

The importance of peas

Field peas are an important rotation crop for Australian farmers. Worth $100 million a year, they add nitrogen to the soil and reduce root disease among following crops.

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 downgrades the peas’ quality and 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.

α-amylase inhibitor GM peas

From 1994 until 2005, CSIRO developed experimental 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 α-amylase, an enzyme that weevils need to help digest starch, a vital part of their diet. This protein, called α-amylase inhibitor (αAI), causes the weevils feeding on beans to starve before they cause any damage.

CSIRO scientists and their collaborators copied the bean gene that produces the protective protein and introduced the gene into the pea. Field trials showed the genetically modified peas were 99.5 per cent resistant to pea weevils.

Risk assessment

CSIRO’s αAI peas underwent a number of tests during development:

1. Laboratory and glasshouse tests [1994 – 2004]
2. Performance studies in the field between 1996 and 2001
3. Feeding trials in mice, pigs and chickens
4. Immune response tests in mice.

The results of these tests are published in scientific literature [see references]

While the lab, glasshouse and field performance trials showed promise in protecting against the pea weevil, the feeding trials with uncooked peas revealed slight negative effects in chickens and pigs after consuming the αAI peas. Using the same peas, there was an unexpected immune response in the mouse trials.

It was believed at the time that the protein behaved differently in the peas which triggered the immune response in the mice.

Given the findings of this research, CSIRO made the decision to discontinue developing the αAI peas in 2005.

Further studies

In order to better understand what may be happening, the CSIRO team investigated the physical structure of the protein in more detail as it appeared in several bean varieties as well as the original αAI peas. This characterisation revealed that there are subtle minor differences in the structure of the αAI in each bean variety and that the αAI in the GM peas possessed a subset of these variants. This raised a question about the apparent immune response in the 2005 feeding study.

Since 2005 various international groups have further investigated the αAI in peas as well as in two additional legumes.

For example, research conducted by Dr Michelle Epstein at the Medical University of Vienna found only minor differences in the immune response of mice compared to significant differences observed in the 2005 study. Dr Epstein and her team investigated the immune reactions of mice fed several varieties of beans and the GM peas, expressing the bean or the GM versions of the α-amylase inhibitor. The mice showed similar levels of immune response no matter which food they consumed. The researchers at the MUV concluded that the immune response in mice was the same no matter whether the inhibitor came from beans, where it naturally occurs, or from peas genetically modified to express the inhibitor.

What is CSIRO doing now?

Between 2001 and 2005 CSIRO researchers ceased the work on the peas and shifted focus to other food legumes, in particular chickpeas and cowpeas, and involves other crop protection genes. This work, while still in the foundational science stage, is very promising with researchers achieving protection against damaging pests. This research is part of our larger program of research addressing global food security issues. CSIRO plays a significant role in global development delivering science that assists developing nations with food security and farming issues. CSIRO adheres to all regulatory requirements for food and environmental safety in its biotechnology research in food crop improvement.

References

Lee R-Y, Reiner D, Dekan G, Moore AE, Higgins TJV, Epstein MM. 2013. Genetically modified α-amylase inhibitor peas are not specifically allergenic in mice PLOS ONE (link to ‘Genetically Modified α-Amylase Inhibitor Peas Are Not Specifically Allergenic in Mice’ journal article online )

Campbell PM, Reiner D, Moore AE, Lee RY, Epstein MM, et al. 2011. Comparison of the alpha-amylase inhibitor-1 from common bean (Phaseolus vulgaris) varieties and transgenic expression in other legumes–post-translational modifications and immunogenicity. Journal of agricultural and food chemistry 59: 6047-6054

Prescott VE, Campbell PM, Moore A, Mattes J, Rothenberg ME, Foster PS, Higgins TJV, Hogan SP. 2005. Transgenic expression of bean α-amylase inhibitor in peas results in altered structure and immunogenicity. Journal of agricultural and food chemistry 53: 9023 – 9030

Collins CL, Eason PJ, Dunshea FR, Higgins TJV, King RH. 2006. Starch but not protein digestibility is altered in pigs fed transgenic peas containing α-amylase inhibitor. Journal of the science of food and agriculture 86: 1894-1899

Li X, Higgins TJV, Bryden WL. 2006. Biological response of broiler chickens fed peas (Pisumsativum L.) expressing the bean (Phaseolus vulgaris L.) α-amylase inhibitor transgene. Journal of the science of food and agriculture 86: 1900-1907.