Overexpression of an elongation factor 1-alpha in Fusarium graminearum leads to reduced fitness

Fusarium graminearum is the causative agent in Fusarium head blight (FHB) of wheat and related cereals. We have generated a F. graminearum mutant overexpressing the gene encoding for elongation factor 1-alpha (FgEF1a), and evaluated changes in pathogenicity. Disease symptoms were reduced by 77.4 % in spray inoculated susceptible wheat cultivar ‘Roblin’, and by 39.1% in spray inoculated Brachypodium distachyon ecotype Bd21, when inoculated with the FgEF1a-overexpression (OX) strain compared to the wild-type. This apparent reduction in pathogenicity seems to be related to a reduction in fitness in the FgEF1a-OX strain, which was observed in mycelium growth and spore germination assays. Eukaryotic EF1a plays a vital role in protein synthesis, but has also been shown to be involved in various other cellular activities including cytoskeletal organization, cell cycle and signalling. Thus, alterations in the physiological levels of EF1a expression could theoretically impact one or more aspects of cell biology/biochemistry, explaining the reduced fitness in F. graminearum. In fact, it has been reported that EF1a overexpression in yeast leads to a similar reduction in fitness due to interactions with actin, thus affecting cytoskeletal function. Additional characterization of FgEF1a-OX is underway to identify changes in cell cycle and morphology to provide insights into the reduced fitness associated with this strain.