Heterodera glycines cysts contain an extensive array of endoproteases as well as inhibitors of proteases in H. glycines and Meloidogyne incognita infective juvenile stages

Heterodera glycines cysts contain proteases, and inhibitors of protease activities in various nematode species. In this investigation, proteases in H. glycines cysts were identified using a commercially available FRET-peptide library comprising 512 peptide pools qualified to detect up to four endoprotease types (aspartic, cysteine, metallo- and serine). Native cyst content (nHglCE) digested peptides in over 96% of the pools with all four protease types identified. Serine and metalloproteases represented nearly 70% of all proteases detected and were examined further. Trypsin (serine) and matrix metalloprotease (MMP) activities were compared among nHglCE, and H. glycines second-stage juvenile (J2) and Meloidogyne incognita J2 extracts. The relative levels of activity were different for all three enzyme sources. Trypsin activity was up to 60-fold greater in M. incognita than in either H. glycines source, while MMP activity was highest in nHglCE and lowest in M. incognita J2. Heat-denatured cyst content (hHglCE) inhibited proteases in all three nematode preparations and was generally greater in M. incognita than in H. glycines . Largest differences (5.2- to 6.4-fold) were observed between M. incognita and nHglCE trypsin and MMP inhibition. In infective juveniles, hHglCE inhibited M. incognita J2 trypsin (IC 50  = 0.64 hHglCEeq reaction −1 ) and MMP (IC 50  = 0.54) more potently than either H. glycines trypsin (IC 50  = 1.34) or MMP (IC 50  = 1.84). Use of three MMP substrates (73, 74 and 80) revealed clear species differences as well as complex associations between activity and inhibition. MMP73 digestion rates were the same in H. glycines and M. incognita but responses to hHglCE inhibition were different. MMP80 digestion rates were different but inhibition was the same. MMP74 digestion rates and inhibition levels were each different between species. These experiments provide further evidence that the H. glycines cyst should be examined as a source of compounds useful for developing nematode control methods.