Pack a Punch Against Fungi
By Jan Suszkiw
January 17, 2001
Agricultural Research Service scientists
are testing new cotton lines whose seed may pack a knockout punch against
The plants' punch is a small protein called a peptide. Shown for
the first time in test tube trials, leaf and seed extracts from cotton plants
expressing the synthetic peptide D4E1 inhibited up to 100 percent of
germinating Aspergillus flavus and other fungi within 30 minutes of
exposure. The next step is to inoculate the cotton bolls with the fungus to see
if D4E1 stops it from germinating on the seed, according to Thomas Cleveland,
who leads ARS
Food and Feed
Safety Research Unit in New Orleans.
A. flavus, one of 25 fungi and bacteria that succumb to D4E1, is of
particular interest because it can contaminate cottonseed with aflatoxin.
Because its harmful to humans and other animals, aflatoxin threatens the
marketability of cottonseed, which is processed into edible oil, a high-protein
meal, and other products valued at $500-700 million annually.
Eventually, according to Cleveland, the peptides could offer a surrogate
defense for cotton plants lacking sufficient resistance to microbial infection.
This also could offset the need for chemical fungicides.
To engineer the cotton, ARS biologists Kanniah Rajasekaran and Jeffrey Cary
first synthesized a gene for making D4E1 using a blueprint of amino acids
the building blocks of all protein from
Dow AgroSciences LLC subsequently
licensed the technology and is collaborating with ARS under a 1998 cooperative
research and development agreement to develop disease resistant cottons.
The researchers used the microbe Agrobacterium tumefaciens to insert
D4E1 into cotton seedling cells and developed a clump of genetically
transformed callus material. From this, they regenerated 100 to 150 plants, but
chose only 10 for further propagation and progeny testing.
The ARS-Dow AgroSciences LLC team is using specialized antibodies and mass
spectrometry techniques to determine how much D4E1 is made by cottonseed, and
pinpoint its location inside cotton cells. ARS is the
U.S. Department of Agriculture's chief
Scientific contacts: Thomas Cleveland or Kanniah Rajah
Rajasekaran, ARS Food and Feed Safety Research Unit, Southern Regional Research
Center (SRRC), New Orleans, La., Cleveland: phone (504) 286-4200, fax (504)
Rajasekaran: phone (504) 286-4482, fax (504) 286-4217,
Ekstrom, Demegen, Inc., (412) 241-2150,
fax (421) 241-2161, firstname.lastname@example.org.