The role of chloroplast-generated reactive oxygen species in the response to a virulent pathogen

ZURBRIGGEN, M.; FRANCESCUTTI, N.; A R KRAPP; HAJIREZAI, M.; CARRILLO, N.

San Miguel de Tucumán

Congreso; XLIV Reunión anual de SAIB; 2009

SAIB

Plants growing in their natural environment are exposed to a wide variety ofpathogens. Upon infection they activate defence mechanisms including theinduction of defence-associated genes and a localised cell death (LCD),conjointly known as the hypersensitive response (HR). There is a concomitantproduction of reactive oxygen species (ROS) in diverse cellular compartmentsreported to play a decisive role in the deployment and modulation of the HR.Transgenic tobacco plants expressing a cyanobacterial flavodoxin (Fld) inchloroplasts, an electron shuttle of prokaryotes and algae, display enhancedtolerance to several abiotic stress conditions by specifically preventing ROSformation in plastids. Fld antioxidant protection in chloroplasts also preventsthe onset of LCD upon exposure to a non-host bacterium leaving unaffectedother aspects of the HR. We use here Fld as a tool to probe the role ofchloroplast generated ROS in the plant response to a virulent pathogen,namely P. syringae pv tabaci. Under normal irradiation conditions, Fldexpression delays the appearance of LCD lesions and oxidative stresssymptoms in infected leaves of transgenic plants in comparison to wild-typesiblings, while failing to provide protection when plants are incubated in thedarkness. These observations are discussed in the context of the role playedby plastid-generated ROS in this type of interaction