Extracellular ATP affects cell viability, respiratory O2 uptake, and intracellular ATP production of tobacco cell suspension culture in response to hydrogen peroxide-induced oxidative stress

Extracellular adenosine 5′-triphosphate (ATP) is a well-known signalling molecule in plants and plays important roles during plant stress response. In the present work, the treatment of tobacco cell suspension culture with exogenous hydrogen peroxide (H 2 O 2 ) caused the decreases of respiratory O 2 uptake, intracellular ATP production, extracellular ATP level, and reduction of cell viability. Combining this observation with the finding that the oxidative phosphorylation uncoupler or the respiratory inhibitor not only decreased intracellular ATP production but also decreased the extracellular ATP level and cell viability, it is suggested that the decrease of extracellular ATP level and cell viability under H 2 O 2 stress could be a result of the suppressed production of intracellular ATP. Treatment with ATP-degrading enzyme, apyrase, also caused the decreases of cell viability, respiratory O 2 uptake, and intracellular ATP production. More importantly, addition of exogenous ATP alleviated the H 2 O 2 -induced decreases of cell viability, respiratory O 2 uptake, and production of intracellular ATP. These results indicate that extracellular ATP could be an important effector in regulating the cell viability, respiratory O 2 uptake, and intracellular ATP production of tobacco cell suspension culture under H 2 O 2 stress.