Tailor-made fruit on research menu

By SIMON COLLINS

State-owned HortResearch is genetically modifying a standard plant to work out which genes produce better flavours, shapes or colours in fruit.

HortResearch scientist Dr Robin MacDiarmid told the NZ Bioethics Conference in Dunedin that genetic research offered the promise of foods specifically tailored to each person's genetic makeup.

Eventually, fruit and other foods could be developed to express the proteins that each person needed to stay healthy.

She said the first step was to genetically modify bacteria and a "model plant" - arabidopsis, or Thale cress, a small weed found alongside railway lines and the like.

It is one of the first species to have had its full genetic structure mapped.

Dr MacDiarmid's gene function technology team is injecting genes into the plant, or "knocking them out", to see the effects in contained glasshouses at HortResearch's Mt Albert research centre.

Genes that have useful effects on flavour or other factors are then used as "markers" to speed up conventional breeding of new fruit varieties. Only fruit trees containing the key "marker genes" are planted in the field.

The fruit trees themselves are technically, not genetically, modified, but their conventional breeding is enhanced by genetic knowledge gained from arabidopsis.

Dr MacDiarmid said HortResearch had no immediate plans for field trials of any genetically modified fruit, and had carried out only one such trial - a project for her own doctoral thesis to grow GM tamarillos in her home town of Kerikeri.

HortResearch chief scientist Dr Ian Ferguson said arabidopsis was a standard plant used in virtually every plant molecular biology laboratory to work out gene functions.

"The whole genome is available publicly, so when we sequence, say, an apple and try to work out what the genes might be coding for, we compare it to arabidopsis," he said.

"It's never perfect, but it's good enough to suggest that it might be the same gene. So arabidopsis has been like the gene standard for comparing gene sequences."

He said HortResearch, Auckland University and other collaborators were bidding for public research funds both to test the effects of certain genes in plants, and then to test the effects of foods containing the modified plant on animals and eventually on humans.

"If you eat something, it has an effect on your physiology and perhaps an enzyme goes up, and you have to have some response at a genetic level," said Dr Ferguson.

New technology will allow the researchers to identify every gene that changes when a rat or a human eats a particular food.

The research programme, if approved, will start in the middle of this year.

How it works

* Scientists use a test plant to work out which genes improve a fruit's flavour, shape and colour.

* Fruit with the same marker genes are then planted commercially.

* The test plant will be genetically modified - but the fruit itself will not.