Single pass cDNA sequencing - a powerful tool to analyse gene expression in preparasitic juveniles of the southern root-knot nematode Meloidogyne incognita

Expressed sequence tags (EST) have been widely used to assist in gene disco very in various organisms (e.g., Arabidopsis thaliana, Caenorhabditis elega ns, Mus musculus, and Homo sapiens). In this paper we describe an EST proje ct, which aims to investigate gene expression in Meloidogyne incognita at t he onset of parasitism. Approximately 1000 5'-end sequence tags were produc ed from a cDNA library made of freshly hatched preparasitic second stage ju veniles (J2). The EST were identified in the primary transformants of the c DNA library, and assigned to nine different functional groups, including (c andidate) parasitism genes. A large fraction of the EST (45%) did not have a putative homologue in public databases. Sixty five percent of the EST tha t could be clustered into a functional group had putative homologues in oth er nematode species. EST were found for virtually all parasitism related ge nes that have been cloned from M. incognita to date. In addition, several n ovel genes were tagged, including a xylanase and a chitinase gene. The effi ciency of EST projects, which produce sequence data for thousands of genes in months time without any difficult pre-selections of mRNA pools, makes ra ndom sequencing cDNA libraries a superior method to identify candidates for parasitism related genes in plant-parasitic nematodes. The sequences in th is paper are retrievable from Genbank with the accession numbers BE191640 t o BE191741, BE217592 to BE217720, BE225324 to BE225598, BE238852 to BE23922 1, and BE240829 to BE240865.