Evidence for cutinase production by Aspergillus flavus and its possible role in infection of corn kernels

Document Type

Article

Publication Date

1-1-1996

Abstract

Aspergillus flavus can infect nondamaged corn kernels and produce aflatoxins before harvest. Experiments were conducted to determine if A. flavus produces cutinase and, if so, to investigate its possible role in kernel infection. Plate assays in vitro showed that A. flavus can grow on purified cutin as the sole carbon source and that it secretes extracellular cutinase, A. flavus grew better in liquid culture at pH 8 than at pH 6. Most cutinase substrate (p-nitrophenyl butyrate [PNB]) hydrolysis activity was in the 30% ammonium sulfate fraction. Two proteins with different PNB hydrolysis activity, designated C1 and C2 were isolated from A. flavus culture filtrates using native polyacrylamide gel electrophoresis. C2 had greater PNB hydrolysis activity than C1. The molecular weights for C1 and C2 were 36 kDa and 22 to 23 kDa, respectively. Kernels pretreated with bacterial cutinase or the 30% ammonium sulfate fraction from A. flavus culture filtrate supported increased levels of aflatoxin production similar to those in wounded kernels. The cutinase activity was strongly inhibited by diisopropyl fluorophosphate (DFP), a specific inhibitor of fungal cutinase, which indicated that A. flavus cutinase may be a serine esterase. Adding DFP to the spore suspension reduced aflatoxin production in kernels of Pioneer 3154 (susceptible) but not kernels of GT-MAS:gk (resistant). These data demonstrate that A. flavus secretes extracellular cutinase when growing on cutin-containing medium and suggest a possible role for cutinase in pathogenicity of A. flavus.

Publication Source (Journal or Book title)

Phytopathology

First Page

824

Last Page

829

This document is currently not available here.

Share

COinS