EFS12- Book of abstracts - Contact

SESSION 2: SECONDARY METABOLITES – BIOCHEMISTRY,
BIOSYNTHESIS, FEED AND FOOD SAFETY
'Awaking' silent gene clusters in the rice pathogen
Fusarium fujikuroi
S. M. Rösler 1,2 , E. M. Niehaus 1 , J. J. Espino 1 , H. U. Humpf 2 , B. Tudzynksi 1
1 Institute for Biology and Biotechnology of Plants, Westfälische Wilhelms-University, Schlossplatz 8,
D-48149 Münster, Germany; 2 Institute of Food Chemistry, Westfälische Wilhelms-University,
Corrensstraße 45, D-48149 Münster, Germany
E-mail: s.roesler@uni-muenster.de
The filamentous fungus Fusarium fujikuroi is a phytopathogenic ascomycete
causing the bakanae disease (“foolish seedlings”) in rice plants. This disease is
triggered by the best known secondary metabolites produced by the fungus,
namely gibberellins. Additionally, F. fujikuroi is able to produce several other well
investigated secondary metabolites which we can easily detect and quantify by
now (i.e. bikaverin, fusarubin, fusarin C). Besides these known ones, the fungus
also possesses the potential to produce a broad spectrum of further, yet
unknown, secondary metabolites. A genome-wide bioinformatical screening
approach revealed that the F. fujikuroi genome encodes 45 key enzymes for
secondary metabolite production, like 18 polyketide synthases (PKSs) and 16
nonribosomal peptide synthetases (NRPSs), all organized in putative gene
clusters.
However, first microarray analyses showed that the majority of these gene
clusters is silent in the wild type under the tested standard conditions (low and
high nitrogen concentration, alkaline and acidic pH), which could explain the
limited knowledge of produced metabolites. The aim of this project is now to
activate silent pathways of F. fujikuroi in order to discover and identify novel
secondary metabolites. Therefore, key enzymes (PKSs) and cluster internal
transcription factors are overexpressed under control of the constitutive gpd
promoter. Comparative expression and product analyses (Northern blot, qPCR,
HPLC/LC-MS) of the wild type and the mutant strains are ongoing. Furthermore,
previous experiments indicated that fungal-plant interaction triggers the
expression of known secondary metabolite clusters. Hence, the expression of the
novel cluster genes will be monitored during rice infection and colonization in
comparison to the expression on maize plants, which are no natural hosts of
F. fujikuroi, in order to gain further insight into the specificity fungal-plant
interaction.
Keywords: Fusarium fujikuroi, secondary metabolites, PKS, infection
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