Location:2009 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 controlling plant-parasitic nematodes comes from a poor understanding of the vulnerable life cycle stages that provide the most important control targets. We discovered that the juvenile stages of plant-parasitic nematodes respond to small molecules that change behaviors required for both hatching and infecting host plants. We demonstrated that these molecules are effective at very low levels, which is important to minimize effects on non-target organisms. In fact, we found that two of the most serious plant-parasitic nematode crop pests, the soybean cyst nematode and the root-knot nematodes, respond differently to the small molecule treatments, which is important in designing control strategies to exploit nematode vulnerabilities. Another important problem involves the lack of information on internal nematode molecules that respond to the environment and are necessary for survival. We discovered a number of nematode proteins that respond to nutritional and temperature stress, with some proteins increasing in amount while others decrease, thereby providing significant new guidance in targeting internal stress proteins for nematode control.
1. Natural molecules control plant-parasitic nematode reproduction at very low levels. One problem with developing safe strategies for nematode management is the need to maximize treatment efficiencies to control the target pest, while minimizing collateral effects upon the environment and non-target species. Therefore, ARS scientists at Beltsville, Maryland and Corvallis, Oregon examined the effects that potent naturally occurring molecules from nematodes and plants have on plant-parasitic nematode behavior and reproduction. They demonstrated that levels of these molecules far below those previously tested effectively change nematode behavior, greatly reducing host plant infection and nearly eliminating nematode reproduction. This discovery is important because it is the first demonstration of such low level effects and will change commonly accepted strategies of nematode control. Therefore, this information is expected to impact scientists who are developing precision treatment strategies for controlling plant-parasitic nematodes for the eventual benefit of growers.
2. Nematode proteins fluctuate in response to environmental stresses. One approach to developing new control measures is to determine which of the tens of thousands of proteins in nematodes are needed for their response to biological and environmental stresses; the biosynthesis of these proteins can then be disrupted in subsequent research. A team of Korean and ARS scientists compared the proteins of a nonparasitic, bacterial-feeding nematode were before and after exposure to heat or deprivation of food. This bacterial-feeding nematode is a useful animal to study most aspects of biology in plant-parasitic nematodes because it can be easily grown in the laboratory. The temperature and starvation stresses were discovered to induce the production of dozens of proteins and suppress the production of dozens more. The results are significant because they provide the first indication that some of these proteins are associated with the resistance of nematodes to nutritional or temperature stress. Consequently, these proteins can now be used by scientists developing new methods for crop nematode control by interfering with the production of stress-related proteins.Masler, E.P. 2008. Responses of Heterodera glycines and Meloidogyne incognita to exogenously applied biogenic amines. Nematology. 10:911-917.