Characterization of endopolygalacturonase of species belonging to the Gibberella fujikuroi complex

The Gibberella fujikuroi complex includes toxigenic and pathogenic fungal species able to produce disease on several economically important crops. In order to understand the involvement of the endopolygalacturonase (endo-PG) in the infection process we have first purified the endo-PG produced in culture by eight species (from two to four isolates of Fusarium verticillioides, F. sacchari, F. fujikuroi, F. proliferatum, F. subglutinans, F. thapsinum, F. nygamai, F. circinatum) belonging to the complex, and then cloned the corresponding genes. The coding sequence of the endo-pg gene permitted to distinguish clearly the different species according to the classification obtained with the partial sequence of the translation elongation factor (TEF), a molecular marker widely used to distinguish identify Fusarium species. The deduced aminoacidic sequence of endo-PGs were very similar among the species and quite identical within the species. The endo-PGs displayed similar properties when assayed against different substrates but showed diverse behaviors in the presence of plant inhibitors (PGIP). In particular, all endo-PGs were not inhibited by PGIP from monocot plants (like aparagus and maize) but presented various degree of inhibition when assayed against the bean PGIP, with the endo-PG from F. verticillioides being the less inhibited. Considering that many species of the G. fujikuroi complex are pathogens of monocot plants, their endo-PG appears particularly adapted to overcome the hindrance of the host PGIPs.