Molecular cloning and characterisation of a venom allergen AG5-like cDNA from Meloidogyne incognita

RNA fingerprinting was used to identify RNAs that were expressed in parasit ic second-stage juveniles of Meloidogyne incognita. but absent from or redu ced in preparasitic second-stage juveniles. A cDNA encoding a putative secr etory protein was cloned from a M. incognita second-stage juvenile cDNA lib rary by probing with a 0.5 kb fragment derived from finger-printing that wa s more strongly expressed in parasitic second-stage juveniles. The cDNA, na med Mi-msp-1. contained an open reading frame encoding 231 amino acids. wit h the first 21 amino acids being a putative secretory signal. In Southern b lot analysis the Mi-msp-1 hybridised with genomic DNA from M. incognita, Me loidogyne arenaria, Meloidogyne javanica, but not Meloidogyne hapla, Hetero dera glycines or Caenorhabditis elegans. In Northern blot analysis a 1 kb t ranscript was detected in both preparasitic and parasitic second-stage juve niles, but nor in adult females of M. incognita. Comparing the predicted am ino acid sequence with protein databases revealed significant similarity to the venom allergen antigen 5 family of proteins in hymenoptera insects and homologues found in several other nematode species. (C) 2000 Australian So ciety for Parasitology Inc. Published by Elsevier Science Ltd. All rights r eserved.