THE PGPR BURKHOLDERIA SP. (AU4i) PROTECTS ARABIDOPSIS THALIANA AGAINST FUNGAL PATHOGENS THROUGH DIRECT INHIBITION AND MODULATION OF DEFENSE AND PLANT CELL WALL METABOLISM

COLAVOLPE, BELÉN; GARRIZ, ANDRES; VILLARREAL, NATALIA; ROSSI FRANCO; ROMERO FERNANDO MATÍAS; RUIZ, OSCAR; SAINI, ADESH; MARINA MARÍA

Barcelona

Congreso; XXI CONGRESO DE LA SOCIEDAD ESPAÑOLA DE FISIOLOGÍA VEGETAL; 2017

Sociedad Española de Fisiología Vegetal

Burkholderiasp. (AU4i), a strain which can acts as PGPR (Plant Growth-Promoting Rhizobacteria)in plants, was previously isolated from pea. We demonstrated that AU4i is ableto grow endophytically on Arabidopsis plants and promote Arabidopsis growthincreasing the number of lateral roots as well as root and shoot dry weight. Toevaluate the potential of AU4i as a biocontrol agent, leaves inoculated withAU4i were challenged with the necrotrophic pathogens Botrytis cinerea andSclerotinia sclerotiorum. The necrotic lesion areas provoked by both pathogenswere reduced in leaves previously inoculated by AU4i. Additionally, AU4i wascapable to inhibit the in vitro growth of B. cinerea, but not of S. sclerotiorum.In other hand, AU4i was able to induce the expression of the jasmonateresponsive marker gene PDF1.2, but not the expression of salicylic acid markergene (PR-1). The protective effect of AU4i against fungal pathogens wasevaluated in Arabidopsis defense signaling pathways mutant plants, coi1(defective in jasmonate perception) and sid2‐2 (defective in salicylic acidsynthesis). Similar protective effect was observed in both lines in comparisonto Col‐0 plants, suggesting the independence of the AU4i protective effect andplant signaling pathways. As well, the effect of AU4i inoculation on plant cellwall metabolism during that endophytic interaction was evaluated. As a resultit was revealed that AU4i modulates host cell wall metabolism, through thedown-­‐regulation of genes involved in hemicellulose and pectins lateral chainsdegradation (AtExp8 and AtAra1, respectively) and the up-regulation of AtPME3,a gene encoding a putative pectin methylesterase involved in pectin main chainesterification. Taken together, our results suggest that Burkholderia sp. AU4imight be a good candidate as a biocontrol agent.