Role of the Plasmalemma H⁺-ATPase in Pseudomonas syringae-Induced K⁺/H⁺ Exchange in Suspension-Cultured Tobacco Cells

Abstract

Activation of a host plasma membrane K+ efflux/net H+ uptake exchange by pathogenic pseudomonads plays an important role in the development of hypersensitivity in tobacco (Nicotiana tabacum). Involvement of the plasmalemma H+-pumping ATPase in this response was investigated. The exchange response of suspension-cultured tobacco cells to Pseudomonas syringae pv syringae was reduced 90% or more by ATPase inhibitors including vanadate, N-ethylmaleimide, and N,N'-dicyclohexylcarbodiimide. The exchange was also strongly inhibited by the protonophore carbonyl cyanide m-chlorophenylhydrazone and by slightly alkaline external pH. Respiratory inhibitors such as oligomycin and sodium azide reduced the exchange by 50% to 75%, while glycolysis inhibitors such as sodium arsenite and sodium iodoacetate decreased exchange by approximately 90%. These results suggest that plasmalemma H -ATPase activity is required for the exchange response and that this may reflect a requirement for a plasmalemma pH and/or electrical potential gradient.The HR3 is characterized by rapid and localized death of plant cells that come into contact with incompatible pathogens and is associated with disease resistance (14). The molecular basis for hypersensitivity and its association with resistance is not well understood. Activation of a plasmalemma K+ efflux/net H+ uptake exchange in tobacco is an early indicator of HR induction by incompatible Pseudomonas syringae pathovars (5, 6). The rapid loss of intracellular K+ along with the disruption of plasmalemma H+ gradients and intracellular pH regulation are believed to contribute to host cell death (5), although other factors such as lipid peroxidation and active oxygen production also appear to be important (11)(12)(13). Induction of the exchange response also occurs in the compatible interaction of P. syringae pv syringae with bean leaf tissue and may promote bacterial multiplication by increasing the availability of nutrients in host intercellular

Involvement of Plasma Membrane Calcium Influx in Bacterial Induction of the K+/H+ and Hypersensitive Responses in Tobacco

“…The K+/H+ response was initially described as a K+ efflux/H+ influx exchange (3), but H+ influx is unproven. Inhibition of this response and HR-associated cell death by increased extracellular pH and ATPase inhibitors (1,27) is consistent with an exchange but does not necessarily exclude K+/HCO3-cotransport as suggested by Murphy and coworkers (14,23) (4). Tn5 resides in a 31 kb gene cluster that has been partially characterized (13 twice by resuspension and subsequent centrifugation in washing medium.…”

“…The K+/H+ response was initially described as a K+ efflux/H+ influx exchange (3), but H+ influx is unproven. Inhibition of this response and HR-associated cell death by increased extracellular pH and ATPase inhibitors (1, 27 …”

Ultraviolet-B Activates Components of the Systemin Signaling Pathway in Lycopersicon peruvianum Suspension-cultured Cells

“…This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. systemin show striking similarities to UV-B signaling, including proton and potassium fluxes (25)(26)(27), increases in intracellular Ca 2ϩ concentrations (28 -30), activation of calmodulin genes (28,31,32), activation of MAPKs (15,22,33,34), activation of an NADPH-dependent oxidase (35)(36)(37), generation of reactive oxygen species (11,25,35,38), and increases in levels of ethylene (27,39,40), and jasmonic acid (39,41,42). However, it is still largely unknown how these signaling events are initiated by UV-B, what their precise cellular function is, and whether wounding/systemin-induced pathways and UV-B-induced pathways utilize some common signaling components.…”

The cDNA Microarray Analysis Using an Arabidopsis pad3 Mutant Reveals the Expression Profiles and Classification of Genes Induced by Alternaria brassicicola Attack

“…Subsequent to the recognition, signal transduction pathways are engaged in host cells. Both generation of reactive oxygen species (ROS) and changes in ion fluxes are observed during the early phases of many plantpathogen interactions Orlandi 1995, Atkinson andBaker 1989). The signals elicit the challenged cells to rapidly collapse and a battery of inducible defenses is deployed in both the challenged cells and surrounding cells (Lamb et al 1989).…”