10th INTERNATIONAL VERTICILLIUM SYMPOSIUM 16-20 ...

CHARACTERIZATION OF NEP-LIKE PROTEINS (NLPS) OFVERTICILLIUM LONGISPORUM ACCORDING TO THEIRRELEVANCE FOR PATHOGENICITY IN BRASSICA NAPUSMALTE BEINHOFF, ARNE WEIBERG, HAIQUAN XU AND PETRKARLOVSKYInstitute of Plant Pathology and Plant Protection, Göttingen University,Grisebachstrasse 6, 37077 Göttingen, Germanywww.gwdg.de/~instphyt/karlovsky/Recently, a new family of small phytotoxic peptides, called Necrosis andEtylen induceng Peptides (NEPs), was described. Since the first NEP were detectedmore than 10 years ago, many other NEP-like proteins (NLPs) were detected invarious microbiological species. Most of them are plant pathogens wich have morethan one copy of NLPs, although it is known that many of these copies arepseudogenes. Conserved sequence structures of NLPs are the GHRHDWE motif inthe centre and cysteine residues at the N-terminus supposed to be relevant of peptideactivity. In many dicotyle plants NLPs have the ability to trigger cell death. Thecellular role of the peptides is not clear yet: NLPs may act as true elicitors byinducing plant immune system or necrotic leasons may result from their phytoxiceffects.In this study we identified and characterized genes for 6 NEPs in Verticilliumlongisporum. These VlNEP genes are homologous genes to VdNEP originating fromVerticillium dahliae. Southern hybridisation was performed to determine to copynumber of the genes in amphidiploid genome of V. longisporum. We analysed theexpression of the gene in hypocotyl tissue of infected Brassica napus plants. ForVlNEP type A, strongly enhanced transcript levels were detected in planta, whichmotivated us to construct knock-down mutants of V. longisporum by RNA-mediatedgene silencing. Typical symptoms caused by V. longisporum such as stunting andearly flowering has rarely been described for the effects of NEPs from other fungi.Infection assays on Brassica napus plants with silenced VlNEP gene type A showed astrong reduction in symptom severity.61