<Emphasis Type="Italic">Aspergillus flavus</Emphasis> hydrolases: their roles in pathogenesis and substrate utilization |
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Authors: | Jay E Mellon Peter J Cotty Michael K Dowd |
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Institution: | (1) US Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, P. O. Box 19687, New Orleans, LA 70179, USA;(2) US Department of Agriculture, Agricultural Research Service, Department of Plant Pathology, University of Arizona, 1140 E. South Campus Dr., Tucson, AZ 85721, USA |
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Abstract: | Aspergillus flavus is a fungus that principally obtains resources for growth in a saprophytic mode. Yet, it also possesses the characteristics
of an opportunistic pathogen with a wide, non-specific host range (plants, animals, and insects). It has attained a high level
of agricultural significance due to production of the carcinogen aflatoxin, which significantly reduces the value of contaminated
crops. To access a large variety of nutrient substrates and penetrate host tissues, A. flavus possesses the capacity to produce numerous extracellular hydrolases. Most work on A. flavus hydrolases has focused on the serine and metalloproteinases, pectinase P2c, and amylase. Many hydrolases are presumed to
function in polymer degradation and nutrient capture, but the regulation of hydrolase secretion is complex and substrate dependent.
Proteinases are employed not only to help access protein substrates, such as elastin that is found in mammals and insects,
but may also play roles in fungal defense and virulence. Secretion of the endopolygalacturonase P2c is strongly correlated
with isolate virulence (against plants) and maceration of cotton boll tissues. In some hosts, secretion of α-amylase is critical
for starch digestion and may play a critical role in induction of aflatoxin biosynthesis. Despite a significant body of work,
much remains to be learned about hydrolase production and utilization by A. flavus. This information may be critical for the formulation of successful strategies to control aflatoxin contamination in affected
commodities. |
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Keywords: | Aspergillus flavus Hydrolases Pathogenesis Nutrient capture Saprophytic |
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