Source: Sydney Morning Herald via Checkbiotech

Gene swap find adds support for GM food

The gene swapping antics of two wheat diseases are set to cause upheaval for biologists and deliver a powerful new argument in favour of genetically modified food, researchers say.

The Australian-led research has provided the first evidence of gene transfers between fungal diseases, finding a gene carrying a critical virulence factor moved from one disease to another.

Published in the journal Nature Genetics, the study suggests the gene transfer happened in the early 1940s and created a new, damaging wheat disease.

"In a broader context, it probably means that genes are transferring all the time, that they're very rarely fixed in the new host," said research leader Professor Richard Oliver, who heads Murdoch University's Australian Centre for Necrotrophic Fungal Pathogens.

"In this particular case, getting the new gene gave (the fungus) a whole important new property and led to the formation of a new disease.

"It's the first time that a fungal gene has been shown to move between different fungal species."

Prof Oliver said the research meant biologists would need to review their "most cherished notion" that species were distinct entities.

"This sort of work shows that's not really the case," he said.

"A species becomes more of a mosaic - some individuals have got some genes and other individuals have got other genes and they can swap genes between other organisms."

The implications for GM food would be difficult to ignore, Prof Oliver said, suggesting nature had always tinkered with gene modification.

"It's really saying that all the gene combinations that we can think of have almost certainly been tried in nature," he said.

"There've been, however, many billions of years to put all these combinations together, and any one that would actually survive and cause an impact in the environment, you could argue has already been tried in the environment and shown (to be) wanting.

"Nature has already been there, done that, and we shouldn't be overly worried about it."

The research discovered the same gene was associated with two different fungal wheat diseases - Yellow Spot and Septoria nodorum blotch.

Yellow spot, also known as tan spot, can cut yield by up to 10 per cent in Australia's main wheat growing areas, while nodorum blotch costs the grain industry more than $60 million a year in lost production.

Professor Oliver made the discovery while scrolling through 17,000 genes thought to be produced by the nodorum fungus, Stagnospora.

His research was part of the Grains Research and Development Corporation project to map the genetic structure of S.nodorum - the southern hemisphere's largest genome study.

He noticed the similarity of a particular gene and the ToxA gene, which causes Yellow Spot.

ToxA is host-specific and only affects wheat and wheat cultivars carrying a susceptibility gene known as Tsn1.

Strains of the Yellow Spot fungus Pyrenophora trici-repentis (PTR), which did not have ToxA, caused only a weak disease.

PTR was considered a mild pathogen until 1941, when it became what is now known as Yellow Spot.

Swiss researchers working with Prof Oliver then provided evidence that a gene transfer from nodorum blotch to PTR enabled it to colonise wheat cultivars containing the Tsn1 gene.

The team concluded that the stronger version of Yellow Spot caused by the gene transfer was spread to wheat fields worldwide through shipments of infected grain.

© 2006 AAP

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