10th INTERNATIONAL VERTICILLIUM SYMPOSIUM 16-20 ...

INVOLVEMENT OF GENES RELATED TO PROGRAMMEDCELL DEATHIN ARABIDOPSIS - VERTICILLIUM DAHLIAE INTERACTIONKOUNTOURI S.D. 1 , PANAGIOTOPOULOU M.X. 1 , KOUTELIERI X. 1 , JONESJ.D.G. 2 AND TSITSIGIANNIS D.I. 1*1Department of Plant Pathology, Faculty of Crop Science, Agricultural University of Athens, IeraOdos 75, Athens 11855, Greece2 The Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, United Kingdom*E-mail: dimtsi@aua.grThe plant hypersensitive response (HR), a form of programmed cell deathwith many common characteristics with the mammalian apoptosis, is associated withthe rapid death of host cells triggered during the entrance of the pathogen in planttissues. When the pathogen elicits a host HR, it fails to multiply to high populationlevels and causes no disease symptoms. Many recent studies indicate the existence ofcommon biochemical pathways of programmed cell death/apoptosis between theplant, mammalian and microbial cells. A detailed bioinformatics analysis of thegenome of Arabidopsis led to the identification of mammalian orthologous genesknown to be involved in programmed cell death. In the present study, we investigatedthe role of mammalian AIF (Apoptosis Inducing Factor) and the frataxin orthologousgenes known to play essential role in apoptosis. Τhe mammalian AIF protein is aphylogenetically old, 57 kDa flavoprotein, which shares similarity to bacterial, fungusand plant oxidoreductases. The frataxin (FT) is involved in iron-sulfur clusterbiosynthesis, controls the oxidative stress response, is essential for development andits defective expression causes Friedreich’s Ataxia in humans. A. thaliana contains 5different putative homologous AIF genes and 1 frataxin. T-DNA knock-out mutantsin these genes were characterized in Arabidopsis and the mutants were tested forwhether they are compromised in HR and disease resistance against differentpathogens included Verticillium dahliae. Characterization of these lines and theresults of the virulence and HR assays will be presented.Another important protein required for the activation of hypersensitiveresponse (HR) and disease resistance against Cladosporium fulvum and Pseudomonassyringae pv. tomato in tomato as well as Tobacco Mosaic Virus (TMV) andPseudomonas syringae pv. tabacci in tobacco is the F-box protein ACF1. ACF1 isexpressed in plant cells in the first 30 minutes after the recognition of theCladosporium fulvum avirulence protein Avr9 by the tomato resistance protein Cf9.Inactivation of the F-box protein in tobacco using gene silencing methodologies leadsto a signification reduction in the development of HR and a significant increase inplant sensitivity to several pathogens. In the present study, characterization of theArabidopsis ACF1 homologues, vfb genes led to the conclusion that these proteins arealso involved in activation of HR. The mutants were studied for the susceptibilityand/or resistance to different pathogens such as Verticillium dahliae,Hyaloperonospora arabidopsis and Pseudomonas syringae pv. tomato DC3000.34