Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 22, 2002
Publication Date: N/A
Interpretive Summary: The goal of this project is to gain new insights into plant/pathogen interaction in order to develop new means to improve crop resistance to disease. Here we report the effect of antioxidants on a plant/bacterial interaction. These antioxidants can mask the oxidative burst which has been shown to be important for triggering resistance mechanisms in plants. By being aware of and quantifying these antioxidants in plants, we can improve our understanding of how plants are able to detect the presence of pathogens and subsequently determine the outcome of the interaction - susceptibility or resistance. This work will benefit ARS and scientists by providing new knowledge about plant/pathogen interactions and help further investigations leading to improved crop disease resistance.
Technical Abstract: Suspension cells of Solanacearum tuberosum and Nicotiana tabacum placed in fresh buffer rapidly produce and maintain significant pools of extracellular antioxidants. The extracellular antioxidant was detected by first adding a known amount of exogenous H2O2 to samples and then immediately measuring the remaining H2O2. The difference between the amount added and amount remaining was used to determine the antioxidant capacity of the sample. This extracellular antioxidant pool attenuates levels of hydrogen peroxide produced during plant-bacterial interactions. Cells of tobacco were inoculated with an isolate Pseudomonas syringae pv. syringae that causes a hypersensitive response. It was apparent when analyzing samples of these treatments that much of the antioxidant capacity had been expended neutralizing the oxidative burst which is characteristic in these interactions. Extracellular phenolics were measured in suspension cells of tobacco and potato and , like the antioxidant capacity, after a brief delay the levels increased within 2 to 4 hr. These extracellular phenolic fractions had strong absorbance within 250 and 350 nm. This property was used to follow oxidation of these phenolics upon reaction with H2O2. This extracellular antioxidant pool is an important consideration in cell suspension studies of the plant-microbe oxidative burst. If the key parameter of an oxidative burst is the detection of reactive oxygen species, the true magnitude may be masked by the extracellular antioxidants.