Characterization of a secreted Fusarium graminearum elongation factor – an elicitor of host defence?

Elongation factor 1-alpha (EF1a) was previously identified in the secretome of Fusarium graminearum cultured in trichothecene-inducing medium. Under these conditions, secreted proteins are predicted to reflect those that are secreted during the infection process in host plants, and are candidate elicitors of host-defence responses. Eukaryotic EF1a is highly conserved in the plant kingdom and is responsible for coordinating aminoacyl-tRNA positioning in the ribosome during peptide bond formation. Its prokaryotic counterpart, EF-thermo unstable (EF-Tu), is also a well characterized pathogen-associated molecular pattern (PAMP). PAMPs are elicitors of plant defence known to interact with host-cell pattern recognition receptors (PRRs), which detect foreign signatures characteristic of pathogens. Sequence analysis of EFTu from a handful of bacterial species showed 30-33% sequence identity with EF1a from a number of plant species. While the prokaryotic EF-Tu is sufficiently foreign to eukaryotic species to elicit plant defense responses, it is not known if the same is true for fungal eukaryotic EF1a which share roughly 70-80% identity with their homologues in plants. Here, a F. graminearum mutant overexpressing FgEF1a was found to have significantly reduced aggressiveness by both point and spray inoculation in five wheat cultivars. In highly susceptible ‘Roblin’ disease was reduced by 60.7% and 77.4% in point and spray inoculated plants, respectively, compared to the wild-type. In highly resistant cultivars ‘CM82036’ and ‘Tenacious’, reduction in visual symptoms were also observed in the point inoculated spikelets. Molecular characterization of FgEF1a and analysis of the effect of this protein on plant host defense will be presented.