The bacteriophytochrome protein modulates virulence in Xanthomonas campestris pv. campestris.

FLORENCIA MALAMUD; HERNAN R. BONOMI; LAILA TOUM; GUSTAVO GUDESBLAT; FERNANDO A GOLDBAUM; ADRIAN A VOJNOV; CARLOS L. BALLARÉ

Mar del Plata

Congreso; XV congreso latinoamericano; XXX reunion argentina de fisiologia vegetal; 2014

Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot of crucifers is a biotrophic-necrotrophic phytopathogen of worldwide economic relevance. In previous work we have shown that Xcc possesses a functional bacteriophytochrome (phy). The phy mutation leads to altered production of xanthan, the principal exopolysaccharide produced by these bacteria that functions as a virulence factor. Our results also showed that the phy mutant is more virulent in Arabidopsis than the wild-type strain. Preliminary experiments showed that when inoculated on npr1 mutant Arabidopsis plants, the differences in virulence between the Xcc wild-type and phy mutant strains are no longer apparent. We have further demonstrated that the infection efficiency of both wild-type Xcc and the phy mutant is greatly reduced on coi1 mutant Arabidopsis plants, which are insensitive to jasmonic acid (JA). Since NPR1 is involved in the majority of the plant defense responses controlled by salicylic acid (SA), our results suggest that the phy mutation increases Xcc virulence by circumventing SA-mediated plant immunity, perhaps by activating JA signaling.