PLANT PHYSIOLOGY , Vol 113, Issue 3 685-693, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Spaceflight Exposure Effects on Transcription, Activity, and Localization of Alcohol Dehydrogenase in the Roots of Arabidopsis thaliana
D. M. Porterfield, S. W. Matthews, C. J. Daugherty and M. E. Musgrave
Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center (D.M.P., C.J.D., M.E.M.), and Department of Plant Biology, Louisiana State University (S.W.M.), Baton Rouge, Louisiana 70803
Although considerable research and speculation have been directed toward
understanding a plant's perception of gravity and the resulting gravitropic
responses, little is known about the role of gravity-dependent physical
processes in normal physiological function. These studies were conducted to
determine whether the roots of plants exposed to spaceflight conditions may
be experiencing hypoxia. Arabidopsis thaliana (L.) Heynh. plants were grown
in agar medium during 6 or 11 d of spaceflight exposure on shuttle missions
STS-54 (CHROMEX-03) and STS-68 (CHROMEX-05), respectively. The analysis
included measurement of agar redox potential and root alcohol dehydrogenase
(ADH) activity, localization, and expression. ADH activity increased by 89%
as a result of spaceflight exposure for both CHROMEX-03 and -05
experiments, and ADH RNase protection assays revealed a 136% increase in
ADH mRNA. The increase in ADH activity associated with the spaceflight
roots was realized by a 28% decrease in oxygen availability in a
ground-based study; however, no reduction in redox potential was observed
in measurements of the spaceflight bulk agar. Spaceflight exposure appears
to effect a hypoxic response in the roots of agar-grown plants that may be
caused by changes in gravity-mediated fluid and/or gas behavior.
