The roles of cellulase enzymes and mechanical force in host penetration by Erysiphe graminis f.sp hordei

Immunofluorescence microscopy with two monoclonal antibodies raised to two Trichoderma reesei cellobiohydrolases revealed antigen localization at the germ tube tips of Erysiphe graminis f.sp. hordei. Cellobiohydrolase II was present principally at the appressorial germ tube tip and cellobiohydrolase I at the primary germ tube tip. Cell turgor measurements, determined by cytorrhysis and plasmolysis experiments revealed that mature E. graminis appressoria produced a maximum turgor pressure of approximately 2-4 MPa, coincident with host cell penetration from the appressorium. Taken collectively, these results imply that host penetration by E. graminis is effected by a combination of enzyme activity and mechanical force. (C) 1999 Academic Press.