Molecular, physiological, and histological evaluations of secreted lipases of Fusarium graminearum during wheat colonisation and in culture

• Applicant: Professor Dr. Wilhelm Schäfer
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 41140498

The ascomycetous fungus Fusarium graminearum (teleomorph Gibberella zeae) is the major cause of Fusarium head blight (FHB) on wheat, barley and other small grain cereals and of ear rot on maize. The cereal-Fusarium pathosystem is characterized by non-race and nonhost specific relationships. The outcome of infection varies between total destruction of the host and minor damage. Virulence of F. graminearum is most probably the consequence of a specific collection of several, additively acting virulence factors. However, only mycotoxins of the trichothecen-class were known to be secreted virulence factors. We have shown recently that a secreted fungal lipase is a new virulence factor, in addition to the already known secreted trichothecenes. Knowledge of the role of all virulence factors in promoting virulence and their distribution in different isolates would contribute to the understanding of the cereal- Fusarium interaction and could offer new approaches to resistance breeding. We identified now three other lipases as virulence factors, whereas we showed that another secreted lipase is not involved in fungal virulence. We want to elucidate why some secreted fungal lipases are important for fungal virulence whereas others are not. Therefore, we ask what distinguishes a „Virulence lipase" from a "saprophytic lipase". We want to do this on transcriptional as well as enzymatic levels. Secondly, we ask how these individual "virulence lipases" are involved in infection and colonization of wheat. We have evidence that a single secreted lipase suppresses a specific wheat defence system. Act other "virulence lipases“ in a similar way, or will we detect different fungal-wheat interactions? Histological evaluation of the infection process of wild type and gene-deletion strains, together with evaluations of host plant defences will answer this question.

• DFG Programme: Research Grants