Characterization of the Maize Defense Response to Cercospora zeina

Maize is an important crop in Africa and one of the major food sources for southern and eastern Africa.  The growth of maize by large-scale and developing farmers is hampered by disease losses, of which grey leaf spot (GLS), caused by the fungus Cercospora zeina, is one of the most severe.  In order to characterize the defense response in a GLS-resistant African maize line, we carried out two transcriptome profiling experiments using the Agilent-016047 maize “whole genome” Microarray, which consists of 42,034 maize reporters.  In experiment 1, we identified differentially expressed genes in RNA extracted from field grown, naturally C. zeina-infected maize material.  In experiment 2, RNA was extracted from glasshouse plants artificially inoculated with C. zeina spore cultures and harvested 3, 6 and 13 days post-infection (dpi).  Considerable overlap in differentially expressed genes was observed between the field infected and 13dpi glasshouse plants.  We used our in-house Maize Microarray Annotation Database (http://MaizeArrayAnnot.bi.up.ac.za/) to annotate this list and found multiple BLAST2GO descriptions for pathogenesis-related proteins, secondary metabolism and signal transduction.  RT-qPCR was used to validate a subset of the identified differentially expressed genes.