PLANT PHYSIOLOGY , Vol 115, Issue 2 617-622, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Changes in Mitochondrial Respiratory Chain Components of Petunia Cells during Culture in the Presence of Antimycin A
A. M. Wagner and M. J. Wagner
Department of Physiology and Biochemistry of Plants, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
When petunia (Petunia hybrida Vilm, cv Rosy Morn) cells are cultured in the
presence of 2 [mu]M antimycin A (AA), respiration proceeds mainly via the
cyanide-resistant pathway. Cyanide-resistant respiratory rates were higher
in mitochondria from AA cells than in control mitochondria. Compared with
control cells, an increase in alternative oxidase protein was observed in
AA cells, as well as an increase in ubiquinone (UQ) content. A change in
the kinetics of succinate dehydrogenase was observed: there was a much
higher activity at high UQ reduction in mitochondria from AA cells compared
with control mitochondria. No changes were found for external NADH
dehydrogenase kinetics. In AA cells in vivo, UQ reduction was only slightly
higher than in control cells, indicating that increased electron transport
via the alternative pathway can prevent high UQ reduction levels. Moreover,
O2 consumption continues at a similar rate as in control cells, preventing
O2 danger. These adaptations to stress conditions, in which the cytochrome
pathway is restricted, apparently require, in addition to an increase in
alternative oxidase protein, a new setup of the relative amounts and/or
kinetic parameters of all of the separate components of the respiratory
network.
