Mechanisms of plant protection against oxalate-producing fungal pathogens by oxalotrophic strains of Stenotrophomonas spp.

ROMERO FM; VILLAREAL N; GÁRRIZ A; MARTÍNEZ G; PIECKENSTAIN FL; MARINA M

Corrientes

Congreso; XXXI Reunión Argentina de Fisiología Vegetal; 2016

Oxalic acid plays a key role as a virulence factor for the necrotrophic fungi Botrytis cinerea andSclerotinia sclerotiorum. Two oxalotrophic strains (OxA and OxB) of the bacterial genusStenotrophomonas were isolated from the rhizosphere of tomato plants. These strains were able toendophytically colonize Arabidopsis leaves and protected them from damage caused by oxalateapplication. OxA and OxB did not induce defence-gene expression in Arabidopsis (PR1 and PDF1.2)and tomato (PR1 and pinII). Both strains induced callose deposition and accumulation of phenoliccompounds. Moreover, OxB down-regulated the expression of plant genes involved in cell wallmetabolism, suggesting that cell wall degradation is attenuated in leaves colonised by this strain. Inaddition, OxA and OxB protected Arabidopsis leaves from S. sclerotiorum and B. cinerea infection,although none of these bacteria inhibited growth of the above-mentioned pathogens in vitro. Moreover,in sid2-2 and coi1 Arabidopsis mutants respectively affected in signalling pathways mediated bysalicylic acid and jasmonates, both isolates exerted a protective effect against fungal pathogens in asimilar way to wild type plants. Results hereby presented suggest that these oxalotrophic bacteriaprotect plants against oxalate-producing pathogens by degrading oxalic acid and strengthening plantcell walls