Oxalotrophic bacteria protect plants from fungal infection independently of classic plant defense signaling pathways

VILLARREAL NATALIA M.; PIECKENSTAIN FERNANDO L.; ROMERO FERNANDO M.; MARTÍNEZ GUSTAVO A.; GÁRRIZ ANDRÉS; MARINA MARÍA

Corrientes

Congreso; XXXI Reunión Argentina de Fisiología Vegetal (RAFV); 2017

Sociedad Argentina de Fisiología Vegetal

Two oxalotrophic bacteria belonging to the   genus  Stenotrophomonas, OxA and OxB, were isolated from the  rhizosphere  of  tomato  plants.  These  strains  were  able  to  growth  endophytically  in  Arabidopsis  leaves and protect them from the damage caused by oxalate application. In addition, OxA and OxB also protected  Arabidopsis   leaves from the infections provoked by two oxalate-producing pathogens, Sclerotinia sclerotiorum   and  Botrytis cinerea,  even though none of the isolates were able to inhibit the growth of these pathogens in  vitro . Neither OxA nor OxB i nduced the expression of defence-related genes  in Arabidopsis   (PR1   and  PDF1.2)  or  tomato  (PR1   and  pinII ).  Moreover,  in  Arabidopsis   sid2 -2 mutant  plants  (affected  in  the  signalling  pathway  mediated  by  salicylic  acid,  SA)  both  isolates originated  the  same  effects  than  those  observed  in  wild  type  plants.  Surprisingly,  plant  protection induced  by  oxalotrophic  bacteria  was  more  evident  in   Arabidopsis   coi1   mutants  (affected  in  the signalling  pathway  mediated  by  jasmonates).  This  was  associated with a  higher  rate  of  callose deposition and production of phenolic compounds in response to OxA and OxB inoculation. Finally, OxB down-regulated  the expression of  genes involved in plant  cell wall  metabolism, suggesting that cell  wall  degradation  would  be  attenuated  during the  interaction  with  this  strain.  Results  hereby presented demonstrate that these oxalotrophic bacteria protect the plant against oxalate-producing pathogens independently of known plant defence pathways.