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United States Department of Agriculture

Agricultural Research Service

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2011 Annual Report

1a. Objectives (from AD-416)
1) Discover nematode proteins and peptides that regulate development, growth and survival, and that provide new targets for controlling nematodes; and 2) Disrupt the function of steroid- or lipid-based regulatory systems unique to plant-parasitic nematodes and critical for their life processes.

1b. Approach (from AD-416)
1) Identify proteases and peptides that control hatching or molting in soybean cyst nematode and root-knot nematode and evaluate specific molecular inhibitors; and identify regulatory proteins, including membrane receptors, involved in the nematode response to its environment and plant host; and 2) Isolate and identify lipids and steroids with likely regulatory roles in plant-parasitic nematodes, and elucidate the biochemical pathways involved in the biosynthesis and metabolism of these compounds; and develop rational strategies for nematode management based upon the utilization of knowledge about the endogenous bioregulatory lipids or steroids in phytoparasitic nematodes.

3. Progress Report
A major problem with developing new methods of controlling plant-parasitic nematodes is that scientists do not know many unique aspects of nematode biology that would make these pests vulnerable to a new control method. We have discovered two vulnerabilities. First, we found that the juvenile stages of plant-parasitic nematodes respond to small natural molecules that change behaviors required for both hatching and infecting host plants. Two of the most serious plant-parasitic nematode crop pests, the soybean cyst nematode and the root-knot nematodes, responded differently to the small molecule treatments. Second, we discovered a number of nematode proteins that respond to nutritional and temperature stress; some of these proteins increase in amount while others decrease, thereby providing significant new guidance in targeting internal stress proteins for nematode control.

4. Accomplishments
1. Natural plant molecules reduce nematode reproduction. Safe strategies for managing plant-parasitic nematodes should be potent and efficient in controlling the target pest, while having minimal impact upon the environment and non-target species. Plant metabolites used as nematode control agents are typically applied at substantial levels. Working with root-knot nematodes, the most economically important nematode crop pest worldwide, we demonstrated that a specific plant defensive metabolite, BITC, rapidly and severely disrupts the infective nematode life stage at very low concentrations, and this disruption results in greatly decreased infectivity. Root-knot nematode reproduction on pepper was reduced 70 percent and reproduction on soybean was nearly eliminated when infective nematodes were exposed to BITC for as little as two hours. This discovery is important because it is the first to suppress plant-parasitic nematode reproduction using greatly reduced levels of a plant chemical. This information is expected to be of great value to scientists developing precision treatment strategies for controlling plant-parasitic nematodes and to growers seeking to decrease chemical use in crop protection.

Review Publications
Cheong, M.C., Na, K., Kim, H., Chitwood, D.J., Paik, Y.K. 2011. A potential biochemical mechanism underlying the influence of sterol deprivation stress on Caenorhabditis elegans longevity. Journal of Biological Chemistry. 286(9):7248-7256.

Riepsamen, A.H., Gibson, T., Rowe, J., Chitwood, D.J., Subbotin, S.A., Dowton, M. 2011. Poly(T) variation in heteroderid nematode mitochondrial genomes is predominantly an artifact of amplification. Journal of Molecular Evolution. 72(2):182-192.

Masler, E.P. 2010. In vitro comparison of protease activities in preparations from free-living (Panagrellus redivivus) and plant-parasitic (Meloidogyne incognita) nematodes using FMRFa and FMRFa-like peptides as substrates. Journal of Helminthology. 84(4):425-433.

Last Modified: 2/23/2016
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