EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
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SESSION 1: FUSARIUM – GENETICS, GENOMICS AND SYSTEMS BIOLOGY<br />
The GABA shunt <strong>of</strong> Fusarium graminearum is<br />
essential for successful colonization <strong>of</strong> wheat spikes<br />
J. Bönnighausen, J. Bormann, W. Schäfer<br />
Molecular Phytopathology and Genetics, University Hamburg, Germany<br />
E-mail: jakobboennighausen@gmail.com<br />
We evaluated the roles <strong>of</strong> the non protein amino acid y-amino butyric acid (GABA)<br />
in the Triticum aestivum - Fusarium graminearum interactions. The GABA shunt is<br />
a conserved stress releated pathway which can be used as an alternative route to<br />
bypass two steps <strong>of</strong> the tricaboxylic acid (TCA) cycle. Its importance for the life<br />
cycle <strong>of</strong> a fungal pathogen has not been described yet. We constructed single and<br />
double deletion mutants for both GABA transaminases.<br />
Growth <strong>of</strong> F graminearum wild type with GABA as the sole N-source strongly<br />
induced deoxynivalenol (DON) production. The ΔΔGAT1;2 mutants were unable<br />
to produce DON after GABA induction in culture, instead we observed by HPLC a<br />
massive accumulation <strong>of</strong> GABA in the mycelium <strong>of</strong> the double mutant. During<br />
vegetative growth, the ΔΔGAT1;2 mutant showed a decreased resistance against<br />
hydrogen peroxide mediated stress. During wheat infection, the individual single<br />
disruptants were only slightly reduced, whereas the double mutant exhibited a<br />
strong reduction in virulence. During initial infection, ΔΔGAT1;2 mutants were<br />
able to infect the inoculated spikelet, crossed the rachis node and grew into the<br />
rachis. Later, they failed to colonize more than one spikelet above and below the<br />
inoculated one, maintaining only app. 25% <strong>of</strong> wild type virulence.<br />
Interestingly, no significant differences were found regarding the expression <strong>of</strong> the<br />
trichothecene biosynthesis genes or the amount <strong>of</strong> DON during infection.<br />
However, the expression levels <strong>of</strong> the SSADH genes and a GABA permease<br />
were highly up-regulated in the ΔΔGAT1;2 mutants, suggesting a disturbed<br />
internal GABA level. Concomitantly, the expression level <strong>of</strong> the citrate synthase<br />
gene, a marker gene for the activity <strong>of</strong> the TCA cycle, decreased 50%. We<br />
conclude that the GABA shunt modulates the fungal stress response, possibly to<br />
ROS, during wheat colonization and is necessary to maintain the primary energy<br />
metabolism under energy demanding conditions.<br />
Keywords: Fusarium, stress metabolism, GABA<br />
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