Saponins and plant defence - A soap story

Saponins are plant glycosides that derive their name from their soap-like properties. They occur in a great many plant species, and have been implicated as pre-formed determinants of resistance to fungal attack. A number of fungi that succeed in breaching these antimicrobial plant defences produce saponin-detoxifying enzymes. The importance of one of these (avenacinase, produced by Gaeumannomyces graminis) in determining host range has been demonstrated. Recently, avenacinase has been shown to be closely related to another saponin-detoxifying enzyme, tomatinase, which is produced by the tomato pathogen Septoria lycopersici, suggesting that common mechanisms for saponin detoxification may be widespread in phytopathogenic fungi.