午夜福利1000集合

WALNUTS grown from genetically modified plants could soon be hitting the
supermarket shelves. The GM roots will beat off costly bacterial infections but
the nuts themselves will be GM-free. The hybrid plants, the first of their kind,
should appease both farmers and consumers wary of GM food.

Fruit tree and vine growers are plagued by Agrobacterium, a bug
which causes cancerous growths called galls in the roots. The bug gets into the
roots via a wound and transfers tumour-causing genes, which invade the plant鈥檚
DNA and the gall starts to form. Now Abhaya Dandekar and a team at the
University of California, Davis, say they can prevent the tumour genes being
expressed by triggering a plant defence mechanism.

They鈥檝e made GM varieties of thale cress and tomato that have versions of the
tumour-causing genes in their DNA. When expressed as mRNA, an intermediate stage
between a gene and a protein, the molecule鈥檚 structure forces it to fold back on
itself. Because plant cells don鈥檛 normally have double-stranded mRNA, they
鈥渟ilence鈥� the genetic material by chopping it up. This prompts the plant cells
to recognise the similar tumour gene mRNA as alien and chop it up.

A standard cultivation technique could be used to ensure that walnut trees
modified in the same way won鈥檛 produce GM fruit. Usually, the chosen fruiting
variety is grafted onto a root stock that copes well with local conditions. In
this case, non-GM plants would be grafted onto modified roots without the two
sets of genes mixing.