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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION AND IMPROVEMENT OF CEREAL GERMPLASM FOR DISEASE RESISTANCE AND WINTER-HARDINESS

Location: Plant Science Research

Title: Interaction between maize seed and Aspergillus flavus

Authors
item Shu, Xisomei -
item Obrian, Greg -
item Livingston, David
item Payne, Gary -

Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: July 25, 2011
Publication Date: N/A

Interpretive Summary: Aspergillus flavus is a fungus that infects corn seeds and contaminates them with aflatoxin. The fungus is localized in the endosperm and aleurone. We wanted to identify the precise seed tissues that are infected by the fungus and to identify where the plant resistance genes are being turned on. We discovered that The fungus moves from the infection site to first colonize the aleurone layer of the seed. While some fungal mycelium was observed in the endosperm around the infection site, the most extensive accumulation of fungus was in the aleurone and at the interface between the endosperm and scutellum. These two tissues expressed two plant defense genes, which suggests that increasing the expression or timing of expression of these genes may confer greater resistance to the fungus. This information will be important in the development of transgenic resistance or the identification of gene markers for marker assisted selection.

Technical Abstract: Aspergillus flavus is an opportunistic fungal pathogen that colonizes maize seeds and contaminates them with aflatoxin. The fungus is localized in the endosperm and aleurone. To investigate the plant microbe interaction, we conducted histological and molecular studies to characterize the internal colonization of A. flavus in maize seed, and to profile transcriptional changes and tissue specific gene expression of maize seed during A. flavus infection. Self-pollinated maize inbred line B73 was inoculated with A. flavus in the field 21-22 days after pollination by wounding the seed with a needle bearing approximately 13 conidia. Seeds were harvested at 3, 4, 5, 6, and 7 days post inoculation and examined for either the presence of the fungus, in situ gene expression, or Illunina RNA-seq transcriptional profiling. Infection of maize kernels by Aspergillus flavus followed a predictable pattern. The fungus moves from the infection site to first colonize the aleurone layer of the seed. While some fungal mycelium was observed in the endosperm around the infection site, the most extensive accumulation of hyphae appeared in the aleurone and at the interface between the endosperm and scutellum. These two tissues expressed the plant defense genes, PRms (Murillo et al., 1999) and UGT (Ma et al., 2010) which suggests that increasing the expression or timing of expression of these genes may confer greater resistance to the fungus. Transcripts from these genes accumulated before we could detect the fungus in this tissue, suggesting that the seed is responding to signals produced by the fungus prior to colonization. This information will be important in the development of transgenic resistance or the identification of gene markers for marker assisted selection.

Last Modified: 7/28/2014
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