Characterization of the venom allergen-like protein (vap-1) and the fatty acid and retinol binding protein (far-1) genes in Meloidogyne hispanica

The root-knot nematode (RKN) Meloidogyne hispanica has been found in all continents associated with a wide host range, including economically, important plants and can be considered a species of emerging importance. Considerable progress has been made to identify nematode effector genes as they are important targets for the development of novel control strategies. The effector genes, venom allergen-like protein (vap-1) and fatty acid and retinol binding protein (far-1), were identified, isolated and sequenced in M. hispanica (Mhi-vap-1 and Mhi-far-1) using the genome information available for the RKNs M. incognita and M. hapla. These genes are differentially expressed during M. hispanica development and their amplification products were observed from cDNA of the eggs, second-stage juveniles (J2) and adult females. However, Mhi-vap-1 showed the highest level of expression in J2. In situ hybridization analysis revealed that the Mhi-vap-1 and Mhi-far-1 transcripts are accumulated within the J2 subventral oesophageal glands. The specific expression in the subventral oesophagel glands and presence of the secretion signal peptide for both genes suggests that these proteins are secreted by the J2 and may play a role in the early parasitic stage of the infection process. These genes were also isolated and sequenced in M. arenaria, M. incognita and M. javanica; and phylogenetic analysis revealed that the predicted protein sequences belonging to M. hispanica and several other species of plant-parasitic nematodes have a high degree of conservation.