New method aids gene study in cereal plants.
Scientists in Japan have developed a practical way to target and delete a specific gene in a plant. Their method should help them to work out which plant genes do what, and may lead to more publicly acceptable genetically engineered foods.
Shigeru Iida and his colleagues at the National Institute for Basic Biology in Okazaki, Japan, knocked out specific genes in rice1, a staple food for more than half the world. To do this they increased the efficiency of a technique called homologous recombination.
Homologous recombination has been used for decades in studies of bacteria and yeast to examine the inner workings of the cell and model human disease. But it has never worked well enough in plants to study their genes. To find out which genes control fruit production or make plants resistant to drought, scientists have had to insert disruptive DNA randomly into plant genomes.
Iida's tweaked the technique to make it almost 10 times more efficient than before - it now works in 1 plant in every 100. This is "in the ballpark of being practical" in the lab, says Benjamin Burr of the Brookhaven National Laboratory in New York, who studies maize and cotton genes. This tool will be especially important when the rice genome sequence is completed later this year, he adds.
"In principle, the technique should also work in other plants, including cereals" such as maize and wheat, says Iida. He anticipates that it will help scientists to discover the function of the thousands of unknown plant genes or to improve agricultural yields.
“The potential to alter the natural copy of a gene and leave nothing else behind could revolutionize genetic engineering Martin Yanofsky , University of California San Diego”
The rice work is nothing new scientifically, points out Martin Yanofsky at University of California, San Diego. In 1997 his group used recombination to knock out a gene in thale cress, Arabidopsis thaliana2. They had to screen 750 plants to find one where the gene was missing.
But Yanofsky concedes that the study is "an enormous achievement that could be applicable to any genes in cereals". He adds: "The potential to alter the natural copy of a gene and leave nothing else behind could revolutionize genetic engineering."
Current techniques concern environmental groups because they modify food crops by inserting mixed stretches of plant and viral or bacterial DNA in random positions that might disrupt more than the target gene. A more accurate approach that tweaks the plant gene in its original spot without recourse to foreign material could allay some of these fears.
Terada, R., Urawa, H., Inagaki, Y., Tsugane, K. & Iida, S. Efficient gene targeting by homologous recombination in rice. Nature Biotechnology, Published online DOI: 10.1038/nbt737, (2002).
Kempin, S.A. et al. Targeted disruption in Arabidopsis. Nature, 389, 802 - 803 (1997).
University of California San Diego