Gene Clustering facilitates Plant Defense

Author:  Iannucci Shandra

Date:  April 2008

Anne Osbourn and her colleagues at the John Innes Centre in the United Kingdom have discovered a plant strategy to regulate genes that code for some defense chemicals. In a study to be published online by Science in late April, the researchers describe how these plants "cluster" the genes necessary for producing potentially toxic compounds. Many of the compounds synthesized by clustered genes, which by nature serve to defend the plants against predation and disease, have important applications in medicine and industry.

Earlier research conducted by Osbourn's team found that avenacin, an antifungal compound produced by oats, is coded for by a series of genes which are grouped next to each other in the oat genome. Corn plants and rice also reportedly cluster some genes for protective compounds.

Plants may have evolved these gene clusters for two reasons. First, clustering genes for any product makes passing the complete sequence on to the next generation more efficient. The clustering might also protect the plant itself against toxic by-products that might result from the creation of an incomplete compound. When researchers blocked the avenacin pathway in oats, the resulting unfinished compound proved toxic to the plant's roots.

"This suggests that gene clusters, as well as keeping beneficial combinations of genes together, may prevent toxic side-effects by strictly controlling where and when the pathway is switched on," claims Ben Field, a member of Osbourn's lab who contributed to the project.

Using the oat's avenacin gene cluster as a template, the researchers searched for similar clusters in the genome of Arabidopsis, a model plant widely used in biological research. In the Arabidopsis genome, researchers found a previously uncharacterized gene cluster coding for a compound called thalianol.

Osbourn's lab plans to use their successful cluster discovery technique to probe the genomes of other plants in order to identify additional clusters producing novel compounds that could be useful to humans. New chemical products discovered using the cluster-detection method could be useful not only in agriculture as a natural means of crop protection, but antimicrobial chemicals such as these may prove to be an exciting new resource of antibiotic and antifungal medicines.

Written by Shandra Iannucci

Reviewed by Allison Wilkinson

Published by Pooja Ghatalia