1.4.20
THE IDENTIFICATION OF GENES INVOLVED IN SYSTEMIC RESISTANCE INDUCED BY BIOCONTROL BACTERIA IN ARABIDOPSIS

KM LEON-KLOOSTERZIEL, CMJ PIETERSE and LC VAN LOON

Section of Plant Pathology, Department of Plant Ecology and Evolutionary Biology, Utrecht University, PO Box 800.84, 3508 TB Utrecht, The Netherlands

Background and objectives
Different forms of induced resistance have been identified in plants. Systemic acquired resistance (SAR) is induced upon infection with a necrotizing pathogen. The plant shows enhanced resistance against a wide range of plant pathogens, which is associated with PR gene expression and salicylic acid (SA) accumulation. Several non-pathogenic Pseudomonas spp. can induce systemic resistance as well, without causing any symptoms themselves [1]. In this induced systemic resistance (ISR) response, SA is not involved and PR proteins do not accumulate . Like SAR, ISR is effective against a broad spectrum of pathogens. To identify genes that are expressed upon induction of ISR, we use a collection of Arabidopsis thaliana enhancer trap and gene trap lines. These lines contain a reporter gene (GUS) without promoter or with a weak promoter, and have been constructed using the Ac/Ds transposon system [2]. We recently started a screen for GUS expression upon root colonization by the non-pathogenic rhizobacterium P. fluorescens strain WCS417r, which is effective in inducing ISR in Arabidopsis. Lines selected in this way can be used to clone and characterize the corresponding genes. Furthermore, they are useful as molecular markers for ISR.

References
1. Pieterse CMJ, van Wees SCM, Hoffland E et al., 1996. Plant Cell 8, 1225-1237.
2. Vroemen CW, Aarts N, In der Rieden et al., 1998. In Morelli G, Last R, eds, Cellular Integration of Signal Transduction Pathways. Springer Verlag, in press.