RAPID CHANGES IN OXIDATIVE-METABOLISM AS A CONSEQUENCE OF ELICITOR TREATMENT OF SUSPENSION-CULTURED CELLS OF FRENCH BEAN (PHASEOLUS-VULGARIS L)

Stressed plant cells often show increased oxygen uptake which can mani fest itself in the transient production of active oxygen species, the oxidative burst. There is a lack of information on the redox status of cells during the early stages of biotic stress. In this paper we meas ure oxygen uptake and the levels of redox intermediates NAD/NADH and A TP and show the transient induction of the marker enzyme for redox str ess, alcohol dehydrogenase. Rapid changes in the redox potential of el icitor-treated suspension cultures of French bean cells indicate that, paradoxically, during the period of maximum oxygen uptake the levels of ATP and the NADH/NAD ratio fall in a way that indicates the occurre nce of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H2O2. The cel ls recover and start producing ATP immediately upon the cessation of H 2O2 production. This indicates that the increased O-2 uptake is primar ily incorporated into active O-2 species. A second consequence of thes e changes is probably a transient compromising of the respiratory stat us of the cells as indicated in expression of alcohol dehydrogenase. E licitor-induced bean ADH was purified to homogeneity and the M(r) 4000 0 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearl y 100% sequence similarity to the amino acid sequence for pea ADH1 (PS ADH1). The cDNA coding for the pea enzyme was used to demonstrate the transient induction of ADH mRNA in elicitor-treated bean cells. Enzyme activity levels also increased transiently subsequently. Increased ox ygen uptake has previously been thought to be associated with provisio n of energy for the changes in biosynthesis that occur rapidly after p erception of the stress signal. However the present work shows that th is rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration.