Tiny Proteins Could Help Cotton Fend off Fungi

Tiny natural proteins derived from moths, frogs and other organisms could give cotton plants a potent anti-fungal agent, new research suggests.

Studies conducted by microbiologist Anthony De Lucca and colleagues show that certain proteins, called peptides, kill Aspergillus flavus and Fusarium fungi. De Lucca is part of an Agricultural Research Service team that’s exploring the peptides’ potential as a built-in defense for cotton.

A. flavus is a soil-dwelling fungus that can contaminate cottonseed with a poisonous substance called aflatoxin. Federal law prohibits farmers from selling as livestock feed any seed containing more than 20 parts per billion of aflatoxin. Fusarium inflicts costly root rots.

Cotton farmers ordinarily apply chemical pesticides to preempt aflatoxin contamination. De Lucca’s team envisions a more environmentally-friendly approach-- genetically engineering cotton plants to make the fungicidal peptides on their own.

Their first order of business: Identify the smallest, most potent peptides possible that the entire plant can produce to kill fungal attackers. One promising peptide is cecropin A, found in cecropia moth caterpillars. The insects make the peptide to protect themselves from infection. Another fungicidal peptide is demaseptin, which some frogs secrete in their moist skin.

In the test tube, cecropin A killed 100 percent of dormant and germinating forms of Fusarium fungi within 30 minutes’ exposure. It also killed nearly all the spores of germinating A. flavus. Scientists conducted the tests using peptide concentrations similar to those that a genetically engineered plant would produce.

Potency against these fungi isn’t the only criterion De Lucca’s team seeks. You can read more about the tricky task of getting plants to mimic these peptides in the June issue of Agricultural Research, a monthly publication of ARS. The story is also on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/jun98/pept0698.htm

Scientific contact: Anthony De Lucca, Food and Feed Safety Research Unit, ARS Southern Regional Research Center, New Orleans, La., phone (504) 286- 4253, fax (504) 286-4419, adelucca@nola.srrc.usda.gov.