## 1 Introduction  
Transgenic plants, engineered with promoters driving the production of conveniently detectable protein products, have proven to be remarkably potent and robust tools for the dissection of gene activities. Such transgenic reporter gene constructions have been used broadly across multiple biological disciplines, in studies ranging from large scale genomic studies of expression patterns of unknown genes and gene networks, to the fine scale mapping of the expression patterns and characteristics of individual specific genes. Reporter gene constructions have employed many detectable protein products, including antibiotic or herbicide resistance proteins that govern growth, enzymatic activities such as \(\beta\)-glucuronidase (GUS) that produce visible precipitates in plant tissues when presented with appropriate substrates, and light emitting proteins such as luciferase and the green fluorescent protein (GFP). While all these classes of reporter gene construction have proven valuable for a variety of applications, constructions using GFP are being utilized ever more widely since the assay procedure does not affect plant growth and development, whereas other methods require the addition of a substrate and usually sacrifice of the plant. To visualize GFP the plant need only be illuminated with a specific wavelength of light and imaged at another wavelength, and the plant is not damaged in the process [1; 2]. As an increasing number of genes become extremely well characterized in terms of the environmental conditions that affect their expression, the promoters of these genes can in turn be deployed as effective in situ and in vivo sensors of plant reactions to their environment. For examples, genes induced by cold, heat, drought, flooding, touch, heavy metals, nutrients, light quality and atmospheric gas content have all been well characterized [e.g. : 3, 4-8]. When the promoters for these genes are coupled with GFP in reporter gene constructions within transgenic plants, those plants become incredibly effective monitors of those particular environmental conditions, identifying both quantitatively and qualitatively the cells, tissues and organs of a plant responding to the condition. Once well characterized in controlled environmental conditions, transgenic reporter gene plants can be deployed to unknown or poorly characterized environments as useful biological monitors to examine the biological response to those environments. Extraterrestrial environments present unique challenges to terrestrial organisms, presenting conditions that have not been faced during biological evolution on Earth. Altered gravity, hard radiation levels, atmospheric compositions and light qualities are all likely to be encountered in orbital, lunar and Martian habitats - habitats most likely to be encountered by humans and the organisms that will accompany humans. Plants certainly have been and will be a part of human spaceflight and extraterrestrial habitation efforts as parts of bioregenerative life support systems [9, 10]. Therefore a clear understanding of plant responses to extraterrestrial environments is not only an interesting study of the limits of biology in the solar system, but also a strategic human life support imperative. Transgenic _Arabidopsis thaliana_ (Arabidopsis) plants employing GUS as part of the reporter construction have been used in orbital space shuttle experiments to examine specific gene responses to the spaceflight environment [11, 12]. Astronauts harvested the plants on orbit and conducted the staining experiments necessary to see the GUS reporter gene activity. The plants were returned to Earth and the results from that study have helped characterize plant responses to spaceflight. However, future spaceflights will have limited access to crew time for experimentation. In addition, early biological experiments in High Earth Orbit, on the moon and on Mars are very likely to be robotic or autonomous missions requiring that gene expression information be returned to Earth via telemetry.