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Title: Comparative histological and transcriptional analysis of maize kernels infected with Aspergillus flavus and Fusarium verticillioides

Author
item SHU, XIAOMEI - North Carolina State University
item Livingston, David
item WOLOSHUK, CHARLES - Purdue University
item PAYNE, GARY - North Carolina State University

Submitted to: Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2017
Publication Date: 12/10/2017
Citation: Shu, X., Livingston, D.P., Woloshuk, C., Payne, G. 2017. Comparative histological and transcriptional analysis of maize kernels infected with Aspergillus flavus and Fusarium verticillioides. Molecular Plant Pathology. 8:2075-2085.

Interpretive Summary: Asperfillus and Fusarium are two fungi that can infect corn kernels and contaminate them with toxins that are harmful to animals and humans. In a histological and genetic examination of corn kernels infected with the 2 fungi we found that 4 hours after infection differences in gene expression were observed between the 2 organisms. Differences in tissue infection as well as gene expression were even more pronounced between 48 and 72h after inoculation. A cluster analysis of the 5863 genes expressed after inoculation indicated that many of the genes were known plant defense genes but many were genes of unknown function. These findings provide a basis for breeders to select genotypes that are resistant to these fungi.

Technical Abstract: Aspergillus flavus and Fusarium verticillioides infect maize kernels and contaminate them with the mycotoxins aflatoxin and fumonisin, respectively. Combined histological examination of fungal colonization and transcriptional changes in maize kernels at 4, 12, 24, 48, and 72 hours post inoculation (hpi) provided a direct comparison of maize seed response to two maize pathogens that can establish different nutritional associations with maize. Simultaneous measurements of fungal colonization and gene transcription in maize kernels during infection also allowed an association of maize seed transcription with stages of fungal colonization. Maize kernels responded by differential gene expression to each fungus within 4 hpi and before the fungi could be observed visually, but more genes were differentially expressed between 48- 72 hpi, when fungal colonization was more extensive. Two-way hierarchal clustering analysis grouped the temporal expression profiles of maize genes expressed in response to each fungus into two broad categories: those expressed 4-12 hpi and those expressed 24-72 hpi. Working under the hypothesis that genes of unknown function may show similar expression profiles to those of known defense related genes, the expression profiles of all 5863 differentially expressed genes over all time points were grouped by hierarchal clustering into 12 clusters. Many clusters were enriched for genes previously associated with defense responses to either A. flavus or F. verticillioides. Within these clusters were genes that lacked either annotation or assignment to functional categories. Grouping genes of unknown function with similarly expressed defense related genes could inform selection of new genes as targets in breeding strategies.