Preparation of the infection court by Erysiphe graminis: II. Release of esterase enzyme from conidia in response to a contact stimulus

Abstract

The release of esterase enzyme activity by conidia of Erysiphe graminis is described as a tropic response to the stimulus of contact with leaf or cellophane surfaces. The release of esterase was completed within 30 minutes of the contact stimulus, and activity was released in two stages. The first began within 2 minutes of conidium contact and the second began between 10 and 15 minutes after contact. A portion of the esterase activity was solubilized in aqueous buffer and a portion remained bound to the conidial wall. Preparations of soluble proteins containing esterase activity were separated by sodium dodecyl sulfate-polyacrylamide and native gel electrophoresis which revealed the presence of several proteins and three zones that possessed esterase activity. The release of enzyme activity was correlated with changes in surface morphology described to occur within the first 30 minutes of initiation by the contact stimulus. The results are discussed in the context of cuticular degradation and preparation of the infection court by the fungus prior to the time of conidium germination.