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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 Title: Genomic analysis of aspergillus flavus pathogenesis

Authors
item Shu, Xisomei -
item Obrian, Greg -
item Nielsen, Dahlia -
item Livingston, David
item Woloshuk, Charles -
item Bhatnagar, Deepak
item Payne, Gary -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 24, 2012
Publication Date: N/A

Technical Abstract: Aspergillus flavus and Fusarium verticillioides colonize developing maize seeds and contaminate them with mycotoxins. Maize genotypes differ in resistance to these fungi, but incorporation of adequate resistance into desirable hybrids has been challenging.Little is known about pathogenesis of seeds by these two fungi, and whetherknown pathways of defense condition host resistance. To better understand the dynamic interaction between these two fungi and maize seeds, we followed tissue colonization and host response of developing seed for three days. Field-grown and greenhouse-grown inbred B73 was inoculated witheitherA. flavus or F. verticillioides 21-22 days after pollination. Seeds were harvested at 4, 12, 24, 48, and 72 hours post inoculation (hpi). In the first 48 hpi, colonization was restricted to aleurone and endosperm tissues that received the inoculum. By 72 hpi, both fungi were detected in the aleurone, endosperm and embryo-endosperm interface. F. verticillioides more extensively colonized the kernel than A. flavus. To determine if known maize defense genes are expressed in tissues colonized by the fungi, RNA in situ hybridization was used to assess transcript accumulation of PRms(Pathogenesis related protein, maize seeds) and UGT(UDP-glucosyltransferases) during infection. PRms was differentially expressed in the aleurone and scutellum of greenhouse and field grown seeds infected with each fungal species. UGT was expressed in the aleurone, endosperm, and scutellum of the field-grown seeds, but was only expressed in the scutellum of the greenhouse-grown seeds.PRms and UGT were expressed in advance of visible colonization by the two fungi. Tissue localization and host response appear similar for these two fungi even though F. verticillioides is an endophyte and A. flavus is predominately saprophytic. Next-Gen sequencing along with Gene Set Enrichment Analysis (GSEA) is being usedto examine maize metabolic pathways that respond to infection by A. flavus. Our initial analyses show increased expression of genes in pathways known to be involved in non-host resistance.

Last Modified: 10/22/2014
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