Inactivation of polygalacturonase and pectate lyase produced by pH tolerant fungus Fusarium moniliforme NCIM 1276 in a liquid medium and in the host tissue.

Fusarium moniliforme NCIM 1276 produced pH dependent an extracellular polygalacturonase (PG) and pectate lyase (PL) at pH 5 and pH 8, respectively. In the extracellular medium about 20.3% PG and 54% of PL protein concentrations were present in the active state at pH 5 and pH 8, respectively, whereas in intracellularly, more than 86% of both protein contents remained in the active state at all pH tested. We found two possible reasons, end-product inhibition and effect of environmental pH on conformation of the proteins after their release into the medium. Additionally, in infected tomato and cauliflower plants, the fungus secreted similar proteins which were located near to the epidermal and vascular regions of the hypocotyls. In infected tissues, between 26.9% and to 41.5% of PG and only 0.84%-13.4% of PL protein concentrations were present in active state. Thus, the medium/cell sap pH and concentrations of substrate/end products seem to play an important role in fungal invasion during plant pathogenesis are discussed with current literature.