Enzyme breakthrough could help protect crops

An antibiotic-producing enzyme in oats could be used to protect major cereal crops from fungal diseases.

Scientists from the Norwich Research Park (NRP) claim that this solution could protect crops from 'take all', a disease estimated to affect half the UK's wheat crops costing the agricultural industry up to £60 million per year.

Take-all is a particularly damaging fungal disease because it infects the roots of the plant and can be passed onto subsequent crops grown in the same field.

But NRP scientists, led by professor Anne Osbourn at the UK-based John Innes Centre (JIC) in collaboration with IGER and the Institute of Plant Molecular Biology in Strasbourg, France found that an enzyme from oats, called Sad2, helps produce a chemical that makes the plant resistant to infections.

Sad2, which functions in the roots, produces an antimicrobial at the site most vulnerable to fungal attack.

"Many plants produce chemicals called 'natural products' that are not essential to growth but have a range of important ecological functions," said Osbourn.

"They can be attractants for pollinating insects or, in this case, protect the plant against diseases.

"Our aim in this work is to understand how these natural products are made and why the ability to produce particular natural products is limited to certain plant species."

Osbourn's data shows that the Sad2 gene has evolved from the most ancient and highly conserved cytochrome P450 family by gene duplication and has then diverged from its original role in making sterols to adopt a new function producing an antimicrobial chemical called avenacin.

The synthesis of avenacin is a multi-step process; the JIC team have already identified five genes coding for different enzymes in this pathway and are currently isolating the others. Unexpectedly, they found these genes were clustered together in the plant's genetic code; clusters of genes that have connected functions are often found in bacteria or fungi but are extremely rare in plants.

"This is only the second gene cluster that has been identified in plants, but I now believe they are more common than previously thought," said Osbourn.

"If we could transfer this gene cluster from oats into other plants, it might be possible to breed cereals that are resistant to devastating crop diseases such as take-all. Our findings also have broad significance for understanding how new metabolic pathways arise in plants, and this is an area that we are now investigating in other plant species such as rice and in the model plant Arabidopsis."

The Sad2 gene technology is the subject of a pending worldwide patent application (International Patent Publication Number WO 2006/044508) assigned to the technology transfer company PBL. PBL are currently working closely with the AgBiotech company DuPont to develop further and commercially exploit applications of the technology.

The research, funded by the Biotechnology & Biological Sciences Research Council and Gatsby Foundation, is published in the Proceedings of the National Academy of Sciences this week.