Abstract
Activation of eukaryotic translation initiation factor eIF5A requires a posttranslational modification, forming the unique amino acid hypusine. This activation is mediated by two enzymes, deoxyhypusine synthase, DHS, and deoxyhypusine hydroxylase, DOHH. The impact of this enzymatic complex on the life cycle of a fungal pathogen is unknown. Plant pathogenic ascomycetes possess a single copy of the eIF5A activated by hypusination. We evaluated the importance of imbalances in eIF5A hypusination in Fusarium graminearum, a devastating fungal pathogen of cereals. Overexpression of DHS leads to increased virulence in wheat, elevated production of the mycotoxin deoxynivalenol, more infection structures, faster wheat tissue invasion in plants and increases vegetatively produced conidia. In contrast, overexpression of DOHH completely prevents infection structure formation, pathogenicity in wheat and maize, leads to overproduction of ROS, reduced DON production and increased sexual reproduction. Simultaneous overexpression of both genes restores wild type-like phenotypes. Analysis of eIF5A posttranslational modification displayed strongly increased hypusinated eIF5A in DOHH overexpression mutant in comparison to wild type, and the DHS overexpression mutants. These are the first results pointing to different functions of differently modified eIF5A.
Highlights
Activation of eukaryotic translation initiation factor eukaryotic translation initiation factor 5A (eIF5A) requires a posttranslational modification, forming the unique amino acid hypusine
deoxyhypusine hydroxylase (DOHH) genes to determine the importance of eIF5A hypusination in F. graminearum
We demonstrate the repercussions of unbalanced expression of the eIF5A activating enzymes deoxyhypusine synthase (DHS) and DOHH, and the tight regulation of eIF5A hypusine modification in the necrotrophic fungus F. graminearum during both vegetative and sexual reproduction, as well as during plant infection
Summary
Activation of eukaryotic translation initiation factor eIF5A requires a posttranslational modification, forming the unique amino acid hypusine This activation is mediated by two enzymes, deoxyhypusine synthase, DHS, and deoxyhypusine hydroxylase, DOHH. Activation of eIF5A requires a posttranslational modification forming the unique amino acid hypusine This posttranslational modification, only found in the eIF5A protein, is mediated by two enzymes, deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH). A recent example of using novel compounds to reduce disease incidence in both wheat and maize was the external application of CNI-1493, a compound that inhibits fungal DHS activity without affecting grain development This specific inhibitor of DHS confirmed that this protein is essential in F. graminearum[12]. In this study we evaluated the importance of the two enzymes which activate eIF5A post-translationally during the life cycle of F. graminearum
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