An efficient cDNA-AFLP-based strategy for the identification of putative pathogenicity factors from the potato cyst nematode Globodera rostochiensis

A new strategy has been designed to identify putative pathogenicity factors from the dorsal or subventral esophageal glands of the potato cyst nematod e Globodera rostochiensis, Three independent criteria were used for selecti on. First, genes of interest should predominantly be expressed in infective second-stage juveniles, and not, or to a far lesser extent, in younger dev elopmental stages. For this, gene expression profiles from five different d evelopmental stages were generated with cDNA-AFLP (amplified fragment lengt h polymorphism). Secondly, the mRNA corresponding to such a putative pathog enicity factor should predominantly be present in the esophageal glands of pre-parasitic juveniles. This was checked by in situ hybridization. As a th ird criterion, these proteinaceous factors should be preceded by a signal p eptide for secretion, Expression profiles of more than 4,000 genes were gen erated and three up-regulated, dorsal gland-specific proteins preceded by s ignal peptide for secretion were identified. No dorsal gland genes have bee n cloned before from plant-parasitic nematodes, The partial sequence of the se three factors, A4, A18, and A41, showed no significant homology to any k nown gene. Their presence in the dorsal glands of infective juveniles sugge sts that these proteins could be involved in feeding cell initiation, and n ot in migration in the plant root or in protection against plant defense re sponses. Finally, the applicability of this new strategy in other plant-mic robe interactions is discussed.