PLANT PHYSIOLOGY , Vol 106, Issue 1 97-102, Copyright © 1994 by American Society of Plant Biologists
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PLANT-MICROBE INTERACTIONS |
Plant Defense Response to Fungal Pathogens (II. G-Protein-Mediated Changes in Host Plasma Membrane Redox Reactions)
R. Vera-Estrella, V. J. Higgins and E. Blumwald
Centre for Plant Biotechnology and Department of Botany, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
Elicitor preparations containing the avr5 gene products from races 4 and
2.3 of Cladosporium fulvum, and tomato (Lycopersicon esculentum L.) cells
containing the resistance gene Cf5 were used to investigate the involvement
of redox processes in the production of active oxygen species associated
with the plant response to the fungal elicitors. Here we demonstrate that
certain race-specific elicitors of C. fulvum induced an increase in
ferricyanide reduction in enriched plasma membrane fractions of tomato
cells. The addition of elicitors to plasma membranes also induced increases
in NADH oxidase and NADH-dependent cytochrome c reductase activities,
whereas ascorbate peroxidase activity was decreased. These results suggest
that changes in the host plasma membrane redox processes, transferring
electrons from reducing agents to oxygen, could be involved in the
increased production of active oxygen species by the race-specific
elicitors. Our results also show that the dephosphorylation of enzymes
involved in redox reactions is responsible for the race-specific induced
redox activity. The effects of guanidine nucleotide analogs and mastoparan
on the activation of plasma membrane redox reactions support the role of
GTP-binding proteins in the transduction of signals leading to the
activation of the defense response mechanisms of tomato against fungal
pathogens.
