THE PLANT CELL, Vol 1, Issue 3 265-273, Copyright © 1989 by American Society of Plant Biologists
Production of Cell Wall-Degrading Enzymes by Aspergillus nidulans: A Model System for Fungal Pathogenesis of Plants
R. A. Dean and W. E. Timberlake
Department of Plant Pathology, University of Georgia, Athens, Georgia 30602
The cell wall-degrading enzymes polygalacturonase and pectate lyase have
been suggested to be crucial for penetration and colonization of plant
tissues by some fungal pathogens. We have found that Aspergillus nidulans
(=Emericella nidulans), a saprophytic Ascomycete, produces levels of these
enzymes equal to those produced by soft-rotting Erwinia species. Induction
of polygalacturonase and pectate lyase in A. nidulans requires substrate
and is completely repressed by glucose. Surprisingly, inoculation of
excised plant tissues with A. nidulans conidia leads to formation of
necrotic, water-soaked lesions within which the organism sporulates. Thus,
A. nidulans has phytopathogenic potential. The release of glucose and other
sugars from wounded tissues may repress pectolytic enzyme production and
limit disease development. Therefore, we tested creA204, a mutation that
relieves glucose repression of some A. nidulans carbon utilization enzymes,
for its effect on production of pectolytic enzymes. creA204 failed to
relieve catabolite repression of polygalacturonase or pectate lyase and had
no effect on disease severity.
