Histology and transcriptional changes of maize seed infected by Aspergillus flavus and Fusarium verticillioides
X. SHU (1), D. Livingston (1), R. G. Franks (1), G. A. Payne (1). (1) North Carolina State University, Raleigh, NC, U.S.A.
Maize ear rots caused by <i>Aspergillus flavus</i> and <i>Fusarium verticillioides</i> are major concerns for human and animal health. Infection and colonization by these two fungi remain poorly understood, and there is limited knowledge of how maize kernels respond to these fungi. We followed colonization, transcriptome changes and tissue-specific gene expression of developing B73 maize seeds inoculated with each of these fungi. Within three days, both fungi colonized in the aleurone, endosperm and embryo tissue, but the pattern for colonization by the two fungi differed. Transcriptome analysis using RNA-seq and qRT-PCR revealed a set of genes that was similarly expressed during infection by these two fungi. RNA in situ hybridization showed that two maize defense genes, <i>PRms</i> (Pathogenesis related protein, maize seeds) and <i>UGT</i> (UDP-glucosyltransferases), were induced in the aleurone and scutellum of seeds inoculated with either <i>A. flavus</i> or <i>F. verticillioides</i>. By comparing histological and in situ hybridization results in adjacent serial sections, we found that these two genes were expressed in the tissue before fungal colonization. These results show that these two fungi colonize three major tissue types of the seed and induce defense gene expression in a tissue-specific fashion in advance of hyphal invasion.
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