ARS | Publication request: Aspergillus flavus and Fusariumverticillioides Induce Tissue Specific Gene Expression of PRms and UGT in Maize Seed before Fungal Colonization

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 4, 2012
Publication Date: N/A

Technical Abstract: Aspergillus flavus and Fusariumverticillioides are fungal pathogens that colonize maize seeds and contaminate them with mycotoxins. To investigate the plant microbe interactions, we conducted histological and molecular studies to characterize the internal colonization of maize seed by the two fungal species, and to localize tissue specific gene expression in maize seed during infection. Field-grown and greenhouse-grown self-pollinated maize inbred line B73 was inoculated with A. flavus and F. verticillioides 21-22 days after pollination by wounding the seed with a needle bearing approximately 13 conidia. Seeds were harvested at 4, 12, 24, 48, and 72 hours post inoculation. During early stages of colonization the fungus is localized in the endosperm at the site of inoculation. Later, the fungus colonizes the aleurone and embryo-endosperm interface. Plant defense related genes PRms(Pathogenesis related protein, maize seeds) and UGT(UDP-glucosyltransferases)are induced in the tissues before fungal colonization. PRms was differentially expressed in the aleurone and scutellum of the seeds infected with both fungal species growing in greenhouse or field. 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 infected with both fungi. Results from these studies show that these fungi colonize specific seed tissues and trigger plant defense response in tissues before fungal colonization. And F. verticillioides is more aggressive than A. flavus with more extensive colonization and earlier induction of plant defense genes. By changing the timing or absolute expression of these genes it may be possible to confer resistance to these fungi. The long-term goal is to identify genetic markers for plant resistance breeding and unravel the plant-microbe interaction. This study will provide critical knowledge in this new area of research and contribute to the improvement of food safety and human health.