Survey of Maize Differential Gene Expression Upon Environmental Exposure to the Tar Spot Pathogen, <i>Phyllachora maydis</i>

Tar spot of maize, caused by Phyllachora maydis, is an emerging threat to crop production across the United States and Canada. Current effective management of the disease includes application of fungicides and use of partially resistant maize varieties. Several studies have focused on mapping of tar spot-resistant loci from maize diversity panels. However, no additional analyses have been reported to further our understanding of the maize defense response to P. maydis. Therefore, prior to the availability of inoculation procedures, we performed transcriptome sequencing from maize leaf tissue exposed to P. maydis from a tar spot-infested field and assessed differential gene transcript expression. Over the course of disease development, leaves were sampled at two time points: 10 and 24 days post-exposure. Differentially expressed genes (DEGs) were determined by comparing gene transcript expression of exposed to non-exposed samples at the respective time points. These experiments revealed 3,160 significant DEGs at 10 days post-exposure and 3,953 significant DEGs at 24 days post-exposure. Further examination of the DEGs revealed transcript enrichment in Gene Ontology biological processes and Kyoto Encyclopedia of Genes and Genomes pathways involved in defense response, photosynthesis, cell wall biogenesis, and plant secondary metabolite biosynthesis. Importantly, several DEGs were previously implicated in having a putative role in P. maydis resistance. Furthermore, construction of gene regulatory networks revealed several transcription factors that may function in the regulation of maize defense responses to P. maydis. This study provides an initial survey of maize responses to P. maydis and identifies candidate genes that may be important in host–pathogen interactions. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .