In planta measurements of oxidative bursts elicited by avirulent and virulent bacterial pathogens suggests that H₂O₂ is insufficient to elicit cell death in tobacco

Abstract

A rapid and localized programmed cell death -the hypersensitive response (HR) -is a widely utilized plant resistance mechanism against pathogens. Studies have implicated H 2 O 2 generation as a key elicitory mechanism in the HR. The causal relationship between the kinetics of the in planta oxidative burst, the HR and certain defence gene expression was examined. H 2 O 2 generation following challenge with avirulent strains of Pseudomonas syringae pv. ( P. s. pv.) syringae occurred in two phases. The effects of ROS generation were investigated using the H 2 O 2 -responsive transgene AoPR10-GUS, the dually responsive (H 2 O 2 and salicylic acid) PR1a-GUS as well as measures of cell death. Co-application of catalase with P. s. pv. syringae into tobacco leaf panels suppressed AoPR10-and PR1a-GUS expression and cell death. Conversely, varying H 2 O 2 generation with glucose: glucose oxidase influenced both defence gene expression and cell death. AoPR10-GUS proved to be primarily responsive to apoplastic not intracellular oxidative stress, suggesting that the apoplasm was a distinctive source of oxidative signals. A biphasic oxidative burst was also observed with virulent P. s. pv. tabaci , which, although delayed compared to that observed during HR, persisted at equivalent levels for a longer period. Taking all these data together we suggest that either (1) additional factors to the apoplastic oxidative burst are required to explain the rapid kinetics of defence signalling and cell death associated with the HR or (2) P. s. pv. tabaci successfully suppresses the effects of H 2 O 2 generation by an unknown mechanism.

Effects of Feeding Spodoptera littoralis on Lima Bean Leaves. III. Membrane Depolarization and Involvement of Hydrogen Peroxide

“…This suggests that apoplast-specific components might be the source of additional signals, the generation of which requires locally high ROS levels that cannot be supplied by diffusion of intracellular H 2 O 2 (Foyer and Noctor, 2005;Mur et al, 2005). MD lima bean leaves reacted fast and dramatically to H 2 O 2 by inducing a strong V m depolarization.…”

“…In response to pathogen invasion, plants mount a broad range of defense responses, including the generation of reactive oxygen species (ROS; Lamb and Dixon, 1997;Mur et al, 2005). ROS are also generated in plant tissues in response to wounding (Angelini et al, 1990;Bradley et al, 1992;Olson and Varner, 1993;Felton et al, 1994;Bi and Felton, 1995;Orozco-Cárdenas and Ryan, 1999), mechanical stimulation of isolated cells (Yahraus et al, 1995;Gus-Mayer et al, 1998), and the treatment of cell suspension cultures with elicitors (Legendre et al, 1993;Mithö fer et al, 1997;Stennis et al, 1998).…”

Nitric Oxide Interacts with Salicylate to Regulate Biphasic Ethylene Production during the Hypersensitive Response

“…Some evidence for this was provided by Moeder et al (2002), who noted that ozone induced biphasic expression patterns in tomato ACS gene expression, with the second increase being dependent on previous ethylene production. In this study, G:GO was injected into the apoplast to generate H 2 O 2 at levels that we had previously shown to be an effective initiator of plant defense (Mur et al, 2005a). G:GO only produced a single burst of ethylene production (Supplemental Fig.…”

“…We here extend our previous investigations on signal production during the nonhost HR elicited by P. s. pv phaseolicola (Psph) in tobacco (Nicotiana tabacum; Kenton et al, 1999;Mur et al, 2000Mur et al, , 2005aMur et al, , 2005b to describe the kinetics of ethylene production during interaction with various P. syringae pathovars, using laser photoacoustic detection (LPAD). These revealed biphasic patterns of ethylene production reflecting elicitation by PAMP and AVR elicitors in a manner reminiscent of biphasic H 2 O 2 and calcium production Grant et al, 2000).…”

Type and cellular location of reactive oxygen species determine activation or suppression of programmed cell death in Arabidopsis suspension cultures

“…1); this agrees with findings from a previous study that showed that catalase temporally suppressed pathogen-induced cell death. 15 The overall balance of various forms of ROS, antioxidants and antioxidative enzymes plays important roles during plant cell signaling. 18 Controlled production of various antioxidants and different ROS forms allows for effective redox signaling and the ratios of reduced to oxidized antioxidants also act as effective cell signals.…”