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A Search for Nematodes' Biological Soft Spots

By Luis Pons
August 10, 2004

Agricultural Research Service scientists are seeking ways to use a nematode's own biology against itself.

Searching for vulnerabilities, ARS Nematology Laboratory researchers in Beltsville, Md., are probing the genes and proteins, susceptibility to toxins--and even the cholesterol--of the microscopic worms that cause more than $10 billion in crop losses each year nationwide.

The focus is on basic processes such as locomotion, egg hatch, growth and development and molecules that help maintain cell health and structure.

Physiologist Edward Masler, molecular biologist Andrea Skantar and plant pathologists Lynn Carta and Susan Meyer are exploring whether heat-shock proteins (HSPs) represent a chink in the worms' armor. As part of these studies, Skantar was the first to report HSP-90 in soybean cyst nematodes. This protein regulates other proteins that control normal cell development and metabolism, and it appears to govern adaptation to environmental extremes in many organisms.

Skantar, Carta and Meyer inhibited HSP-90 in nematodes by exposing the worms' eggs to geldanamycin, a bacteria-produced compound. They now plan to examine these bacteria as biocontrol agents against nematodes.

Masler's work led to the discovery in cyst nematodes of HSP-70, which helps them respond to stress, and to the first description of the actin gene in the worms. Actin is a protein active in muscular contraction, cellular movement and cell shape maintenance. The researchers seek to design actin-control agents specific to nematodes but harmless to other organisms.

Carta evaluated the nematode-killing properties of toxins found in Bacillus thuringiensis, a common bacterium that poses no threat to humans but targets nematodes' gut. She found four toxins that damaged at least two nematode species.

Meanwhile, ARS zoologist David Chitwood of the Nematology Laboratory and researchers from Yonsei University in Seoul, South Korea, seek to learn exactly how disruption of sterol metabolism actually kills nematodes. Sterols are chemical compounds found in cells. The most common of these is cholesterol.

Read more about this research in the August issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.