Submitted to: Journal of Helminthology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2012
Publication Date: March 1, 2013
Citation: Masler, E.P. 2013. A comparison of the FMRFamide-like peptide proteolytic activities of preparations from two plant-parasitic nematodes (Heterodera glycines and Meloidogyne incognita): possible targets for novel control. Journal of Helminthology. 87(1):71-77. Interpretive Summary: Plant-parasitic nematodes attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. Because several chemical pesticides used to control nematodes have been withdrawn from use, growers possess a critical need for the discovery of environmentally and economically sound nematode control agents. One approach to discovering new ways to control nematodes is to disrupt their normal biology by interfering with molecules found within the nematode. In this study, we found that small protein molecules called FLPs, that are produced naturally by nematodes and are essential for their survival, are degraded differently in the soybean cyst nematode and the Southern root-knot nematode, and that we can affect the enzymes involved in this degradation. These results are significant because they show that nematode molecules can be manipulated directly to control these pests and protect host plants when they are most susceptible to nematode attack. Consequently, this information will be used by researchers in the agrochemical and agricultural biotechnology industries who are developing safe, selective methods for nematode control.
Technical Abstract: Plant-parasitic nematodes require a family of neuropeptides (FLPs) to regulate their physiology, and FLPs are an important target of research into novel nematode control agents. A critical component in FLP activity is degradation by nematode proteases. Proteolytic activities in extracts from the plant parasitic nematode Heterodera glycines and Meloidogyne incognita were examined for their abilities to digest three FLPs labeled for use in enzyme assays. The FLPs were chosen to include sequences distributed across all nematode species (KSAYMRFa and KHEYLRFa), and a sequence confined to a narrow range of plant-parasitic nematodes (KHEFVRFa). Species variations were observed among substrate affinities, reaction rates, and effect of protease inhibitors. Affinities for KHEYLRFa and KSAYMRFa in H. glycines were each higher than those for the same substrates in M. incognita. The affinity for KHEFVRFa was higher in M. incognita than in H. glycines. Reaction rates for KHEYLRFa were the same for both species, but KSAYMRFa and KHEFVRFa reaction rates were each nearly two-fold higher in M. incognita than H. glycines. Digestion of KSAYMRFa was strongly inhibited in each species by a serine protease inhibitor (AEBSF) and a metalloproteinase inhibitor (EDTA), but M. incognita was more sensitive to inhibition. 1mM AEBSF inhibited M. incognita activity 62.6 % more than H. glycines activity, and 1mM EDTA inhibited 36.6% more. Serine protease activity differed significantly between the two species as detected by inhibition. Maximum inhibition of M. incognita serine proteases was 76% at 1.85mM AEBSF while maximum inhibition of H. glycines was only 40 % at 1.85mM AEBSF, and was not increased with additional AEBSF.