THE PLANT CELL, Vol 4, Issue 9 1101-1111, Copyright © 1992 by American Society of Plant Biologists
Adhesion Pad Formation and the Involvement of Cutinase and Esterases in the Attachment of Uredospores to the Host Cuticle
H. Deising, R. L. Nicholson, M. Haug, R. J. Howard and K. Mendgen
Universitat Konstanz, Fakultat fur Biologie, Phytopatologie, Universitatsstrasse 10, W-7750 Konstanz, Germany
We have investigated the basis of adhesion of uredospores of the obligately
parasitic rust fungus Uromyces viciae-fabae to leaves of its broad bean
host. Upon contact with an aqueous environment, spores form a structure
that we have termed an adhesion pad. The adhesion pad is formed by both
living and autoclaved spores, but only adhesion pads formed by living
spores adhered to the cuticle of leaves of the host plant. Treatment of
living spores with the serine-esterase inhibitor diisopropyl
fluorophosphate prevented the adhesion of the pad to the leaf surface,
suggesting a functional role for esterase or cutinase in the process of
adhesion. A cutinase and two nonspecific serine-esterases were found to be
localized on the surface of spores. These enzymes were released rapidly
from the spore surface upon contact with an aqueous environment. The
addition of the cutinase and the nonspecific esterases to autoclaved spores
restored their ability to adhere to the host cuticle. Thus, whereas pad
formation appears to be a passive response to the aqueous environment, the
actual adhesion of pads to the host cuticle appears to depend on the
cutinase and esterases associated with the spore surface. These results
suggest a new role for cutinases and serine-esterases in the fungal
infection process.
