A pectate lyase (PL1) from the tomato vascular wilt pathogen Fusarium oxysporum f.sp. lycopersici was previously characterized, and evidence was obtained for its production in planta. The gene encoding PL1 was isolated from a genomic library of F. oxysporum f. sp. lycopersici. Pl1 encodes a 240 amino-acid polypeptide with one putative N-glycosylation site and a 15 amino-acid N-terminal signal peptide. PL1 showed 89%, 67%, 55% and 56% identity with the products of the Fusarium solani f.sp. pisi pelA, pelB, pelC and pelD genes, respectively. A single copy of the gene was detected in different formae speciales of F. oxysporum. The pl1 transcript was observed during growth on polygalacturonic acid sodium salt and tomato vascular tissue, but not on pectin or glucose. RT-PCR showed pl1 expression in roots and stems of tomato plants infected by F. oxysporum f.sp. lycopersici.