Cloning and sequence analysis of a polygalacturonase-encoding gene from the phytopathogenic fungus Sclerotinia sclerotiorum.

The phytopathogenic fungus Sclerotinia sclerotiorum produces a number of extra-cellular pectin-degrading enzymes. We have cloned and determined the complete sequence of a gene (pg1) encoding an endopolygalacturonase (PG1). The coding region consists of a non-interrupted 1143-bp open reading frame. S. sclerotiorum pg1 was compared to other fungal PG-encoding genes. Basic transcription control sequences were identified in the 5' non-coding region. The deduced amino acid (aa) sequence (380 aa) of the enzyme is compared to seven fungal PG sequences and shows a high level of identity (41.5 to 59.8%). Predicted secondary structures were compared, revealing a similar protein organization most probably in antiparallel beta sheets. Hybridization analysis using a pg1 0.65-kb BamHI fragment as a probe allowed the identification of seven different recombinant phages from a genomic library. Analysis of the hybridizing restriction fragments suggests that PG-encoding genes are organized as a family.