CSIRO abandons GM pea project

CSIRO Plant Industry researchers have abandoned a project to develop a genetically modified field pea with resistance to the pea weevil, Bruchus pisorum.

The project was shelved in October 2003, when CSIRO researchers discovered that the transgene, whose protein completely protected the pea seeds against infestation by the weevil's larvae, reduced productivity in pigs and poultry when it was experimentally added to their feed formulae.

The transgene codes for a protein that inhibits an enzyme called alpha amylase, which is essential for the weevil's larvae to digest starch - in other words, the larvae starve.

Project leader, Plant Industry Assistant Chief Dr TJ Higgins, said at the time that, while the transgenic protein posed no health hazard to the livestock, or to humans, profit margins in the pig and poultry industry were too low to tolerate a 10 per cent drop in productivity.

But since then, immunologists at the Australian National University's John Curtin School of Medical Research, have shown that the transgenic protein causes mild inflammation in the lungs of laboratory mice fed on the transgenic peas.

Working with Higgins' team, the JCSMR researchers, led by Dr Simon Hogan and Prof Paul Foster, showed that the inflammation was probably a result of subtle differences in the way beans and peas glycosylate the transgenic protein.

In the pea genome, glycosylation -- a process that modifies the structure of the protein by adding sugar molecules after the protein is synthesised -- appears to make the protein allergenic when fed to the mice. Immune cells in the gastric mucosa monitor food passing down the digestive track, and in rare cases, can trigger a systemic immune reaction.

Foster said CSIRO had informed his team that, unlike other GM pest-resistant crops like Bt cotton and Bt maize, the procedure used to express the transgene in peas involved a pathway that involved several processing steps, including glycosylation.

Higgins said the fact that the problem had been detected, and the project shelved, before the pea was commercialised, demonstrated the strength of the case-by-case approach to developing and testing GM crops.

There has been only other, similar episode in a quarter of a century of developing transgenic crops.

US researchers had transferred a gene for a Brazil nut protein into soybean, in an attempt to increase animal productivity. While the modified soy was never intended for human consumption, researchers had later realised the protein was potentially dangerous to individuals with a severe allergy to Brazil nuts, so the project was shelved.

In the CSIRO project, the nature of the glycosylation process, and the fact that the problem arose as a consequence of the protein being expressed in a different genetic background, meant the change could not have been predicted in advance.

Higgins said the transgenic pea was almost 100 per cent effective in resisting pea weevil attack, which causes production losses of up to 30 per cent in some years. The GM pea was developed to reduce the use of pesticides to control the weevil.

The JCSMR team did not test whether the protein caused a similar inflammatory reaction in humans, but after discussions with Higgins' team, it had been decided to wind up the project.

"This work strongly supports the need for case-by-case examination of plants developed using genetic modification, and the importance of decision-making based on good science."

Higgins said the project was originally conceived as a test-bed for new techniques for genetically modifying legumes, which are the major source of protein in many developing nations.

Higgins said even though the GM field pea project had been wound up, the technology was very valuable, and CSIRO was considering applying it to other legume research projects.