Detalle de: Requirement for either a host- or pectin-induced pectate lyase for infection of Pisum sativum by Nectria hematococca

Fungal pathogens usually have multiple genes that encode extracellular hydrolytic enzymes that may degrade the physical barriers in their hosts during the invasion process. Nectria hematococca , a plant pathogen, has two inducible pectate lyase (PL) genes ( pel ) encoding PL that can help degrade the carbohydrate barrier in the host. pel A is induced by pectin, whereas pel D is induced only in planta . We show that the disruption of either the pel A or pel D genes alone causes no detectable decrease in virulence. Disruption of both pel A and pel D drastically reduces virulence. Complementation of the double disruptant with pel D gene, or supplementation of the infection droplets of the double disruptant with either purified enzyme, PLA, or PLD, caused a recovery in virulence. These results show that PL is a virulence factor. Thus, we demonstrate that disruption of all functionally redundant genes is required to demonstrate the role of host barrier-degrading enzymes in pathogenesis and that dismissal of the role of such enzymes based on the effects of single-gene disruption may be premature.