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Cloning and Disruption of pgx4 Encoding an In Planta Expressed Exopolygalacturonase from Fusarium oxysporum

April 2000 , Volume 13 , Number  4
Pages  359 - 365

F. I. García-Maceira , Antonio Di Pietro , and M. Isabel G. Roncero

Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain

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Accepted 20 December 1999.

Fusarium oxysporum f. sp. lycopersici, the causal agent of tomato vascular wilt, produces an array of pectinolytic enzymes, including at least two exo-α1,4-polygalac-turonases (exoPGs). A gene encoding an exoPG, pgx4, was isolated with degenerate polymerase chain reaction primers derived from amino acid sequences conserved in two fungal exoPGs. pgx4 encodes a 454 amino acid polypeptide with nine potential N-glycosylation sites and a putative 21 amino acid N-terminal signal peptide. The deduced mature protein has a calculated molecular mass of 47.9 kDa, a pI of 8.0, and 51 and 49% identity with the exoPGs of Cochliobolus carbonum and Aspergillus tubingensis, respectively. The gene is present in a single copy in different formae speciales of F. oxysporum. Expression of pgx4 was detected during in vitro growth on pectin, polygalacturonic acid, and tomato vascular tissue and in roots and stems of tomato plants infected by F. oxysporum f. sp. lycopersici. Two mutants of F. oxy-sporum f. sp. lycopersici with a copy of pgx4 inactivated by gene replacement were as virulent on tomato plants as the wild-type strain.

© 2000 The American Phytopathological Society