Oxidative metabolism in plant/bacteria interactions: characterization of a unique oxygen uptake response of potato suspension cells

Plant suspension cells have been shown to respond to bacteria or microbial elicitors by producing active oxygen as well as increasing oxygen uptake. Here we characterize a unique two stage oxygen uptake response of potato suspension cells to heat-killed bacteria. Stage I occurred within minutes after the addition of heat-killed bacteria; the potato suspension cells responded with a rapid increase in oxygen uptake and reached a steady state approximately 50 % greater than the initial basal rate, Stage 2 began 20 30 min after this new steady state was achieved and was characterized by a slow increase in the oxygen uptake rate over the remaining 90 min period, Calculation of the total oxygen consumption by the plant cells indicated that only a small fraction of the increased oxygen uptake was due to the concomitant production of reactive oxygen species. The protein kinase inhibitor, K-252, inhibited the oxygen uptake response by 80 90 %, suggesting the involvement of protein phosphorylation in the oxygen uptake response. The alternate oxidase inhibitor, SHAM, inhibited the elicited oxygen uptake response by about 25 % while a combination of SHAM and KCN almost completely blocked respiration as well as the elicited response, The data indicate that mitochondrial respiration and, in Particular, the alternate oxidase, play a significant role in the elicited oxygen uptake response of potato cells.