10th INTERNATIONAL VERTICILLIUM SYMPOSIUM 16-20 ...

RNAi-BASED GENE SILENCING OF A PUTATIVETRANSCRIPTION FACTOR IN VERTICILLIUM LONGISPORUMAND ITS ROLE IN PATHOGENICITYHAIQUAN XU, MALTE BEINHOFF, ARNE WEIBERG AND PETRKARLOVSKYwww.gwdg.de/~instphyt/karlovsky/Verticillium longisporium (VL) is a soil-borne pathogen of Brassicaceaeinfecting economical important crops like oil seed rape (Brassica napus). Due to itssystemic infection chemical plant protection is insufficient for crop protection. Thedesign of resistant varieties is on demand and the discovery of new gene targets beinginvolved in VL pathogenicity will help us to develop improved resistance traitsagainst VL.In a cDNA-AFLP approach investigating the effect of xylem sap metabolitesof B. napus on the transcriptome of VL we identified a regulated transcript Vl12.1showing homology to a zinc-finger transcription factor (ZnF_C2H2). We profiled theexpression of Vl_12.1 during infection of B. napus in root/hypocotyl tissue and founda reduced transcript accumulation in reference to in vitro grown mycelium in a xylemsimulating artificial medium, indicating a suppression of this gene during theinfection process.pBLAST sequence analysis of Vl_12.1 showed the highest homology to theace1 transcription factor in Trichoderma reseii. In this saprophytic fungus ace1 actsas a regulated transcriptional suppressor of cellulase and xylanase genes.We applied RNAi technology for gene silencing of this ace1-like gene in VL byexpressing a gene-specific RNA-hairpin. Gene-silenced mutants did not show anyvisual difference in triggering typical infection symptoms in B. napus. Also testing foralterations in cellulase activities on cellulose-containing agar medium indicated nodifference between the silenced mutants and the VL wild type. To further clarify roleof the VL ace1-like gene in cellulase regulation as well as in pathogenicity to B.napus an over-expression of this gene is under construction.58