PLANT PHYSIOLOGY , Vol 110, Issue 1 137-145, Copyright © 1996 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
The Complexity of Enzymic Control of Hydrogen Peroxide Concentration May Affect the Regeneration Potential of Plant Protoplasts
A. de Marco and K. A. Roubelakis-Angelakis
Department of Biology, University of Crete, P.O. Box 1470, 71 110 Heraklio Crete, Greece
Total peroxidase, NADH-peroxidase, ascorbate peroxidase, superoxide
dismutase, and catalase activities were measured in tobacco (Nicotiana
tabacum) leaves and in regenerating and nonregenerating protoplasts
isolated from the same tissue and cultured for 2 weeks. The specific ranges
of H2O2 concentration at which the enzymes scavenging the active forms of
oxygen may efficiently operate and the activities of those enzymes were
determined in an extract from tobacco leaves and in dividing and
nondividing tobacco mesophyll protoplasts. The overall H2O2-scavenging
enzyme activities were similar in both protoplast populations during the 2
to 3 d of culture. After 3 d, the regenerating protoplasts started to
divide and both the antioxidant enzyme activities and the total peroxidase
activity increased; in contrast, the viability and the H2O2-scavenging
enzyme activities in nonregenerating protoplasts dramatically decreased.
Surprisingly, the regenerative potentiality in dividing protoplasts was
specifically correlated with a higher NADH-peroxidase activity, which
resulted in a net H2O2 accumulation in the cells. Light, which causes the
accumulation of active forms of oxygen in photosynthetic organelles, also
stimulated catalase and ascorbate peroxidase activities in dividing
protoplasts. We suggest that the localization of H2O2 rather than its
absolute concentration might be responsible for oxidative stress and that
controlled amounts of H2O2 are necessary to allow proper cell-wall
reconstitution and the consequent cell division.
