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Tissue Specific Hypoxic Stress of Arabidopsis.  J.A. Barney, A.-L. Paul, R.J. Ferl Dept. of Horticultural Sciences, University of Florida, Gainesville

   Hypoxic conditions induce Alcohol dehydrogenase (Adh) gene expression in Arabidopsis thaliana.  In this study, transgenic Arabidopsis were used to monitor signal transduction as a result of variable hypoxic stress conditions. The development of a transgenic line of Arabidopsis using the Adh gene promoter attached to в-glucuronidase (GUS) reporter gene has facilitated tissue specific monitoring Adh expression in response to abiotic stress.  Plants were exposed environments of 2% and 10% oxygen levels for 24 hours to establish a base-line level of transgene expression, and then histochemical staining was utilized to show gene expression.  Signal transduction was further examined by tissue specific stressing of the plants.  By allowing only the roots or shoots to be exposed to hypoxic conditions, we were able to observe if signal transduction occurred.  Tissue specific stress included blanketing the roots using agar growth medium for controlling the amount of oxygen available to the roots.  Medium blankets containing gadolinium chloride, a calcium inhibitor, were utilized to control effects of calcium signal transduction. In addition; plant tissues were selectively exposed to atmospheres composed of 2%, 10% or 21% oxygen, and Adh/GUS expression monitored throughout the plants.  The level of carbon dioxide remained constant at 0.035% balanced by nitrogen.  The Adh/GUS staining patterns of the plants grown in 10% oxygen were only minimally affected by the hypoxic conditions, as seen at the ends of the roots and no expression in the leaves or apex.  Plants grown at 2% oxygen showed expression throughout the roots as well as in the apex and leaves of the plant. When 10% and 2% oxygen concentrations were applied only to the roots of the plant, no signal was noted in the apex or leaves at 10% oxygen; however, at 2% oxygen Adh/GUS expression appears in the apex of the plant, even though the shoots of the plant received ambient levels (21%) of oxygen. 

(Supported by: NASA: NAG10-316)