Rapid changes in oxidative metabolism as a consequence of elicitor treatment of suspension-cultured cells of French bean (Phaseolus vulgaris L.)

Abstract

Stressed plant cells often show increased oxygen uptake which can manifest 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 measure oxygen uptake and the levels of redox intermediates NAD/NADH and ATP and show the transient induction of the marker enzyme for redox stress, alcohol dehydrogenase. Rapid changes in the redox potential of elicitor-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 occurrence of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H2O2. The cells recover and start producing ATP immediately of H2O2 production. This indicates that the increased O2 uptake is primarily incorporated into active O2 species. A second consequence of these changes is probably a transient compromising of the respiratory status of the cells as indicated in expression of alcohol dehydrogenase. Elicitor-induced bean ADH was purified to homogeneity and the M(r) 40,000 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearly 100% sequence similarity to the amino acid sequence for pea ADH1 (PSADH1). 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 oxygen uptake has previously been thought to be associated with provision of energy for the changes in biosynthesis that occur rapidly after perception of the stress signal. However the present work shows that this rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration.

Involvement of a Glycerol-3-Phosphate Dehydrogenase in Modulating the NADH/NAD+ Ratio Provides Evidence of a Mitochondrial Glycerol-3-Phosphate Shuttle in Arabidopsis

“…The expression pattern of GPDHc1 is most likely a reflection of the variable requirement for cytoplasmic redox adjustment in different developmental stages since pronounced changes of pyridine nucleotide patterns were associated with induction of flowering (Bonzon et al, 1983). There is also a significant body of literature describing environmental factors affecting NADH/NAD þ ratio in plants ( Oh-hama and Miyachi, 1959;Yamamoto, 1963;Ogren and Krogmann, 1965;Kuraishi et al, 1968;Bonzon et al, 1983;Zagdanska, 1989;Robertson et al, 1995). We used ABA treatment to simulate stress conditions because increased ABA is a shared signaling event in various stress responses.…”

Tansley Review No. 86 Accumulation of phytoalexins: defence mechanism and stimulus response system

“…One of the earh' responses of plant tissues to treatment with eiicitors or challenge with pathogens is an 'oxidati\"e burst' that is characterized b\-increased oxygen uptake (Robertson et al, 1995) et al, 1995). It has been suggested therefore that the critical trigger for the elicitation process is the formation of the superoxide anion or other active oxygen radicals Legendre et al, 1993;Mehedy.…”

Molecular cloning of the cDNA encoding a stress-inducible protein phosphatase 1 (PP1) catalytic subunit from French bean (Phaseolus vulgaris L.)

“…The kinetics o f m R N A induction are rapid enough to suggest that the PP1 could be involved in adjusting to the redox stresses arising from the early events upon elicitor perception by French bean cells. Certainly there are early changes in bean cells in the levels of A T P and N A D H in response to elicitor [20]. A rapid depletion of A T P in the system [20] and a reciprocal increased level of c A M P [1] have been observed which m a y both be related to the profound changes in the oxidative state of the cells following elicitor treatment.…”

“…Since PP1 is considered to be regulated by A T P its expression could also be related to the redox status of the cells which changes rapidly upon elicitation [ 17,20]. The kinetics o f m R N A induction are rapid enough to suggest that the PP1 could be involved in adjusting to the redox stresses arising from the early events upon elicitor perception by French bean cells.…”