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The identification and characterization of the poplar flagellin receptor

PtFLS, an Arabidopsis FLS2 orthologue

        Abstract

The bacterial flagellin (flg), a protein of the flagellum of gram negative bacteria is an important virulence factor for pathogenic bacteria and acts as a “general elicitor” in animals and plants. Elicitor activity is attributed to the most conserved domain within the Nterminal part of flagellin (Felix et al. 1999 and Bauer et al. 2001) comprising 22 amino acids (QRLS TGSR INSA KDDA AGLQ IA) and in most cases derived from Pseudomonas syringae. This peptide (flg22) exhibits full elicitor activity of basal defence by inducing responses in Arabidopsis thaliana and tomato in subnanomolar concentrations. Even though the flagellin protein is high conserved, there are sequence variations in some plant associated bacteria e.g. Rhizobium melioti and Ralstonia solanacearum, which might indicate a selection pressure for non-detectable flg22-domains (Felix et al.1999; Pfund et al. 2004). The shorter epitope derived from Escherichia coli, flg15 E. coli, is highly active as an elicitor in tomato but not in Arabidopsis thaliana or Nicotiana benthamiana. I used these species-specific differences in flagellin perception abilities for the identification and characterization of the poplar flagellin receptor PtFLS. Transiently expression of the PtFLS gene in Nicotiana benthamiana was functional because PtFLS-GFP fusion acquired responsiveness to flg15 E. coli to which this species is normally unresponsive. Additional, corresponding protein accumulation of PtFLS-GFP fusions were indicated by several Western blots. Similar experiments of PtFLS-GFP fusions in Arabidopsis thaliana must be done in further studies, but stable transformation with PtFLS in Arabidopsis thaliana were successful in T1 generations of Ws-0 and fls2-c plants. Thus, PtFLS encodes a functional flagellin receptor. Besides, this study gives evidence that the FLS2 receptor is conserved.

 

Ulrike Rüdiger-Ludwig

 

for further information contact me on uli@fls2.de or uli@fls2.info

 

see also EFR / EF-Tu

 

Keywords : FLS2 orthologue - flg22 – Innate immunity - PAMP - Populus trichocarpa

 

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