Pathogenic and phenotypic traits of a Fusarium graminearum strain overexpressing translation elongation factor 1-alpha

Fusarium graminearum is the predominant causative agent in Fusarium head blight (FHB) of wheat and related cereals. We have generated a F. graminearum mutant (FgEF1a-OX) overexpressing a gene encoding for elongation factor 1-alpha (FgEF1a). Eukaryotic EF1a plays a vital role in protein synthesis, but has also been shown to involve in various other cellular activities including cytoskeletal organization, cell cycle and signalling. Compared to wild-type, the FgEF1a-OX mutant reduced the disease symptoms in susceptible wheat cultivar, Roblin by 77 and 61 % in spray and point inoculations, respectively. A reduction in visual symptoms was also observed in highly resistant cultivars, CM82036 and Tenacious. This apparent reduction in pathogenicity seems to be related to a loss of fitness in the FgEF1a-OX strain, which was observed through mycelial growth and spore germination assays. The germination of wild-type macroconidal spores was 60% at 6 h and increased to nearly 100% by 9 h incubation. In contrast, only 15 and 53 % of the FgEF1a-OX macroconidia were germinated at similar time points of incubation. The alteration in physiological levels of EF1a might have negatively impacted one or more aspects associated with cell biology/biochemistry. A report on EF1a overexpression in yeast leading to a similar loss in fitness due to interactions with actin suggests an altered cytoskeletal function in F. graminearum. Additional characterization of FgEF1a-OX is underway to identify changes in cell cycle and morphology to get in-sight into fitness loss associated with this strain.