PLANT PHYSIOLOGY , Vol 109, Issue 2 659-665, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Chill-Induced Changes in the Activity and Abundance of the Vacuolar Proton-Pumping Pyrophosphatase from Mung Bean Hypocotyls
C. P. Darley, J. M. Davies and D. Sanders
Plant Laboratory, Department of Biology, University of York, P.O. Box 373, York YO1 5YW, United Kingdom
Changes in the properties of extractable vacuolar H+-pumping
pyrophosphatase (V-PPase) and vacuolar ATPase activities in
chilling-sensitive seedlings of mung bean (Vigna radiata) were
investigated. Following chilling at 4[deg]C for 48 h, both hydrolytic and
proton-pumping activities of the V-PPase increased 1.5- to 2-fold over
controls and remained elevated even after 72 h at low temperatures.
Vacuolar ATPase levels did not change significantly throughout the chilling
regime. However a large increase in alcohol dehydrogenase activity during
chilling suggests a shift toward fermentative metabolism, which can be
expected to decrease ATPase activity in situ. Western blotting of vacuolar
membrane-enriched fractions from control and treated plants has confirmed
that the changes in V-PPase activity are mirrored by increases in the
amount of pump protein. Results suggest a specific role for the V-PPase in
protecting chill-sensitive plants from the injurious effects of low
temperatures via the maintenance of the proton gradient across the vacuolar
membrane.
