Submitted to: Journal of Helminthology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2010
Publication Date: 12/30/2010
Citation: 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. 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 Because several chemical pesticides used to control nematodes have been withdrawn from use, there is a critical need for the discovery of environmentally and economically sound nematode control agents. One approach to discovering new methods to control nematodes is to identify ways to disrupt their normal biochemical processes by using chemicals that occur naturally inside the nematode. We have previously reported the discovery in plant-parasitic nematodes of small protein molecules called FLPs, which are produced naturally by nematodes and are essential for their survival. In this paper, we describe the discovery that two different species of nematodes, one a plant parasite and the other a bacterial feeder, degrade nearly 20 different FLPs at different rates and in a nematode-specific manner. The discovery is significant because it shows that nematode-specific metabolism of key FLPs can be used to target plant-parasitic nematode control without affecting beneficial nematodes. Consequently, this information will be used by researchers in the agrochemical and agricultural biotechnology industries developing safe, selective methods for nematode control.
Technical Abstract: Extracts prepared from the free-living nematode Panagrellus redivivus and the plant-parasitic nematode Meloidogyne incognita were each capable of degrading a broad range of nematode FMRFamide-like peptides (FLPs), key regulatory messengers of nematode growth and development. Clear quantitative differences between the two extracts were observed using FMRFamide as a substrate. Extract potency assessed at 50 % substrate degradation was 1.77-fold greater for P. redivivus than for M. incognita, and potency assessed at 90 % substrate degradation was 2.46-fold greater. An overall potency difference was also present when screening the degradation of 17 nematode FLPs, but it was not universal. The mean % digestion of 8 of the 17 FLPs (76 %) was 2-fold greater with P. redivivus extract than with M. incognita extract (38 %), but the means for the other 9 FLPs were not different. Three FLPs (KPSFVRFa, AQTFVRFa, RNKFEFIRFa) were degraded extensively by the extracts of both species, and two FLPs (SAPYDPNFLRFa, SAEPFGTMRFa) were degraded 2.9-fold and 5.3-fold greater, respectively, with M. incognita extract than with P. redivivus extract. The ability of each extract to degrade FMRFa and KSAYMRFa was significantly reduced by using peptide analogs containing single D-amino acid substitutions, and the substitution effects were positional. Both FMRFa and KSAYMRFa were competitive substrates for aminopeptidases in each extract, but only the competitive ability of FMRFa was reduced by D-amino acid substitution. The variety and complexity of nematode FLP degradation are discussed.