Evidence that polygalacturonase is a virulence determinant in Erwinia carotovora.

Polygalacturonase (PG) was purified from Erwinia carotovora EC. A hybrid cosmid, pSH711, that encodes PG activity but not pectate lyase activity was identified from an E. carotovora genomic library by an immunological screening method. A cell extract of Escherichia coli cells containing pSH711 was able to produce plant tissue maceration when spotted on carrot, potato, or turnip slices. In addition, the E. coli strain containing this plasmid was able to macerate carrot, potato, and turnip slices. Our results suggest that PG plays an important role in soft-rot disease.