NP Keller; R Butchko; A Sarr; T Phillips
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Abstract: Different Aspergillw species f$avus, parasilinrs, and nidulons), which produce- difFecent intermediates and end products of the aflatoxin pathway (norsolorinic acid, NOR; sterigmatocystin, ST; and aflatoxin, Am, are useful in studying the maize-Asper~illus-mycotoxinin teraction. Aspergilhx AF mutants, which produce NOR (a visible orange intermediate of both ST and AF), were used to visualize mycatoxin deposition in host and fungal tissues. NOR was seen in specific maize kernel tissues (embryo and aleurone) and specific fungal tissues (substrate mycelium but not spomlating mycelium) within 24 h after inoculation of kernels or growth media. ST and AF were found in the same maize tissues but only after organic extracts of these tissues were quantitated by timeconsuming chromatography methodologies. Mycotoxin production and fungal ingress by all three Aspergillus spp. were subject to regulation by the developmental stage oi the maize kernel: both fungar colonizatian and NOR deuosition shifted from ernbrvonic to endosoerm tissues in germinating maize kernels, The appearan& of NOR flag&d the progress of fungal invasion through kernel tissues. We suaest that NOR mutants may be useful tools to identify Likely infection sites in maize kernels and that the genetically characterized A. nidulans may be useful in helping identify global regulatory mechanisms in the maize-Aspergillus-my~otoxni interaction.