ASGSB 1999 Annual Meeting Abstracts

REPORTER GENE EXPRESSION IN ALTERED GRAVITY ENVIRONMENTS. R.J. Ferl, H.J. Chung, C.J. Daugherty, E.A. Bihn, C.R. Lyerly, M Dolan-O'Keefe and A-L. Paul. Dept of Horticultural Sciences and the Biotechnology Program, University of Florida, Gainesville, FL

We have used transgenic Arabidopsis containing an Adh/GUS promoter reporter fusion gene to assay the influence of gravity and gravitational environment on stress gene activity. It is widely accepted that the Arabidopsis Adh gene is greatly induced by metabolic stresses, cold, ABA and hypoxic stresses. GUS expression driven by the Adh promoter was examined by growing transgenic plants in different growing systems, and during episodic microgravity aboard the KC-135. While roots from vertical-positioned plates had no Adh/GUS expression, roots grown in 1g on horizontal-positioned plates showed high Adh/GUS expression levels. Additional results indicate that growth on horizontal plates resulted in induction of Adh/GUS expression that is consistent with hypoxic conditions within the agar of the root zone. Surprisingly, Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca²⁺ signal transduction from the root to the shoot.

Results from KC-135 tests indicate that there is a rapid onset of reporter gene shoot expression that occurs within the first 20 parabolas, and continues through the rest of a typical parabolic flight. The expression levels rapidly return to baseline after landing, and re-occur during the next flight. Centrifugal reconstruction of the hyper-g phase of the flight profile indicates that it is the micro-g portion of the KC-135 flight that causes induction. These same transgenic plant lines will fly on STS-93 as the PGIM-01 payload. Preliminary flight data may be available.

(Supported by NASA: NAG10-0145)

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