A BASIC SERINE-PROTEASE FROM PAECILOMYCES-LILACINUS WITH BIOLOGICAL-ACTIVITY AGAINST MELOIDOGYNE-HAPLA EGGS

Scanning electron micrographs of the nematode-egg-parasitic fungus Pae cilomyces lilacinus infecting eggs of the root-knot nematode Meloidogy ne spp, suggested the involvement of lytic enzymes. When grown on a li quid mineral salts medium, supplemented with different substrates as t he sole N- and C-source, the fungus produced an extracellular protease , Colloidal chitin, vitellin and intact eggs of the root-knot nematode Meloidogyne hapla induced proteolytic activity that was repressed by glucose. The protease was partially purified from the culture filtrate by affinity chromatography, It has a molecular mass of 33.5 kDa, a ph optimum of 10.3, a temperature optimum of 60 degrees C and an isoelec tric point above ph 10.2. The enzyme was completely inhibited by PMSF. The amino acid sequence, as derived from the nucleotide sequence of a cDNA clone, had high homology with several subtilisin-like serine pro teases. It was shown that the purified enzyme degrades vitellin. The p rotease quantitatively bound to nematode eggs, and eggs incubated with the purified protease eventually floated, Incubation of the purified protease with nematode eggs significantly influenced their development as demonstrated by time-lapse microscopy. Immature eggs were highly v ulnerable to protease treatments, whereas those containing a juvenile were more resistant. In addition, hatched larvae were not visibly affe cted by the protease, It can be concluded that the serine protease mig ht play a role in penetration of the fungus through the egg-shell of n ematodes.