The ascomycetous fungus Fusarium graminearum is an important plant pathogen causing Fusarium head blight disease of wheat and barley. To understand early developmental stages of this organism, we followed the germination of macroconidia microscopically to understand the timing of key events. These events, recorded after suspension of spores in liquid germination medium, included spore swelling at 2 h, germination tube emergence and elongation from conidia at 8 h and hyphal branching at 24 h. To understand changes in gene expression during these developmental changes, RNA was isolated from spores and used to interrogate the F. graminearum Affymetrix GeneChip. RNAs corresponding to 5813 genes were detected in fresh spores and 5146, 5249 and 5993, respectively, in spores incubated in germination medium after 2, 8 or 24 h (P < 0.001). Gene expression data were used to predict the cellular and physiological state of each developmental stage for known processes. Predictions were confirmed microscopically for several previously unreported developmental events such as manifestation of peroxisomes in fresh spores and nuclear division resulting in binuclear cells within macroconidia prior to spore germination. Knowledge of stage-specific gene expression and changes in gene expression levels between developmental stages are an important first step to understanding the molecular mechanisms responsible for spore germination and development.
Bibliographical noteFunding Information:
The authors thank Karen Hilburn for excellent technical support. This project was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service (Award #2004-35604-14327) and the German Federal Ministry of Education and Research (BMBF) within the BFAM framework (031U112C / 212C). The US Wheat and Barley Scab Initiative is also acknowledged for the continuing support of research. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.
- Gibberella zeae