Plant J. (2012): Arabidopsis wat1 (walls are thin1)-mediated resistance to the bacterial vascular pathogen, Ralstonia solanacearum, is accompanied by cross-regulation of salicylic acid and tryptoph... | Arabidopsis mediated resistance to the bacterial vascular pathogen |

The inactivation of Arabidopsis WAT1 (Walls Are Thin1), a gene required for secondary cell wall deposition, conferred a broad-spectrum resistance to vascular pathogens, including the bacteria Ralstonia solanacearum and Xanthomonas campestris pv. campestris, and the fungi, Verticillium dahliae and V. albo-atrum. The introduction of NahG, the bacterial salicylic acid (SA)-degrading salicylate hydroxylase gene, into wat1 restored full susceptibility to both R. solanacearum and X. campestris pv. campestris. Moreover, SA content was constitutively higher in wat1 roots, further supporting a role for SA in wat1-mediated resistance to vascular pathogens. By combining transcriptomic and metabolomic data, we demonstrated a general repression of indole metabolism in wat1-1 roots as shown by a constitutive down-regulation of several genes encoding proteins along the indole glucosinolate (IGS) biosynthetic pathway and reduced amounts of tryptophan (Trp), IAA and neoglucobrassicin, the major form of IGS in roots. Furthermore, wat1 susceptibility to R. solanacearum was partially restored when crossed with either trp5, an overaccumulator of Trp or Pro35S:AFB1-myc in which IAA signaling is constitutively activated. Our original hypothesis placed cell wall modifications at the heart of wat1 resistance phenotype. However, the results presented here point to a mechanism involving root-localized, metabolic channeling away from indole metabolites to SA as a central feature of wat1 resistance to R. solanacearum.


Nicolas Denancé*, Philippe Ranocha*, Nicolas Oria, Xavier Barlet, Marie-Pierre Rivière, Koste A. Yadeta, Laurent Hoffmann, François Perreau, Gilles Clément, Alessandra Maia-Grondard, Grardy C.M. van den Berg, Bruno Savelli, Sylvie Fournier, Yann Aubert, Sandra Pelletier, Bart P.H.J. Thomma, Antonio Molina, Lise Jouanin, Yves Marco, Deborah Goffner