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.
Proteolytic activities in extracts from the plant-parasitic nematodes Heterodera glycines and Meloidogyne incognita were examined for their abilities to digest three FRET-modified peptide substrates representing members of the large FMRFamide-like peptide (FLP) family in nematodes. Included were 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. K m values for KHEYLRFa (1.48 ± 0.34 μm) and KSAYMRFa (2.13 ± 0.24 μm) in H. glycines were each lower (P< 0.05) than those for the same substrates in M. incognita (5.26 ± 1.30 μm and 3.90 ± 0.61 μm, respectively). The K m of KHEFVRFa was lower (P< 0.05) in M. incognita (5.83 ± 0.36 μm) than in H. glycines (11.01 ± 1.26 μm). Reaction rates (V max/min/μg) for KHEYLRFa were the same for both species, but KSAYMRFa and KHEFVRFa digestion rates were each nearly twofold higher (P< 0.05) in M. incognita than in H. glycines. Digestion of KSAYMRFa was strongly inhibited in both species by 4-(2-aminoethyl)-benzenesulfonyl-fluoride-HCl (AEBSF) and EDTA, but M. incognita was more sensitive (P< 0.05) to inhibition. AEBSF and EDTA (both at 1 mm) inhibited M. incognita activity 62.3% and 36.6% more, respectively, than H. glycines activity. Serine protease inhibition differed significantly (P< 0.05) between the two species. Maximum inhibition of M. incognita (76%) occurred at 1.85 mm AEBSF while maximum inhibition of H. glycines was 40% at 1.19 mm AEBSF.
Nematology Laboratory, United States Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705-2350, USA. edward.masler@ars.usda.gov
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D000818:Animals; D019835:FMRFamide / Q000378:metabolism*; D007700:Kinetics; D010447:Peptide Hydrolases / Q000378:metabolism*; D010944:Plants / Q000469:parasitology; D011480:Protease Inhibitors / Q000378:metabolism; D059748:Proteolysis; D014431:Tylenchoidea / Q000378:metabolism*
D011480:Protease Inhibitors; D019835:FMRFamide; D010447:Peptide Hydrolases