2010 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.
A major problem with controlling plant-parasitic nematodes comes from a poor understanding of the vulnerable stages of the nematode life cycle. These provide the most important targets for designing new methods of nematode control, are in contact with the host plant, and are dependent upon specific behaviors for infection. We discovered that small, natural plant molecules that affect nematode behavior potently and specifically strongly suppress plant-parasitic nematode infectivity and reproduction on host plants. We also found that plant-parasitic nematodes cannot properly metabolize peptide mimics of natural nematode control peptides. Because these peptides are needed for normal nematode infectivity behavior, this discovery provides an additional option for designing control strategies that exploit nematode vulnerabilities in combination with potent and specific natural molecules.
Natural plant and nematode molecules control plant-parasitic nematode behavior at very low levels. Ideally, safe strategies for managing nematodes must be potent and efficient in controlling the target pest, but have minimal impact upon the environment and non-target species. ARS scientists at Beltsville, Maryland and Corvallis, Oregon demonstrated that infectivity of root-knot nematodes, the most economically important nematode crop pest worldwide, was reduced nearly 20-fold on pepper and nearly 100 percent on soybean by using very low levels of a specific plant metabolite to disrupt the infective nematode life stage. These ARS scientists also demonstrated that mimics of nematode regulatory peptides are abnormally metabolized in root-knot nematodes, and cannot function properly. These discoveries are important because they are the first that quantify high impact suppression of plant-parasitic nematode reproduction by low levels of a plant chemical, and the first that demonstrate the disruption of plant-parasitic nematode metabolism by a modified nematode peptide. Therefore, this information is expected to be of great value to scientists who are developing precision treatment strategies for controlling plant-parasitic nematodes for the benefit of growers.
Joo, H.J., Wim, Y.H., Jeong, P.Y., Jin, Y.X., Lee, J.E., Kim, H., Jeong, S.K., Chitwood, D.J., Paik, Y.K. 2009. Caenorhabditis elegans utilizes dauer pheromone biosynthesis to dispose of toxic peroxisomal fatty acids for cellular homoeostasis. Biochemical Journal. 422(1):61-71.
Chitwood, D.J., Perry, R.N. 2009. Reproduction, physiology and biochemistry. In: Perry, R.N., Moens, M., Starr, J.L., editors. Root-Knot Nematodes. Wallingford, UK: CAB International. p. 182-200.
Masler, E.P., Zasada, I.A., Sardanelli, S., Rogers, S.T., Halbrendt, J.M. 2010. Effects of benzyl isothiocyanate on the reproduction of Meloidogyne incognita on Glycine max and Capsicum annuum. Nematology. 12(5):693-699.