In 2008, the 'Cell Wall' experiment is scheduled to be launched and conducted on the International Space Station with the European Modular Cultivation System (EMCS). The main aim of this in-orbit plant science experiment is to elucidate the effect of gravitational conditions on supporting tissue formation in plants, thereby gaining new insight into the molecular mechanisms by which plants adapted to the land environment. In this first space experiment with in-orbit control experiments, we will specifically aim to elucidate the expression profiles of several candidate genes encoding proteins that are involved in the construction and restructuring of the secondary cell wall in the stem of Arabidopsis thaliana grown both in microgravity and 1G conditions. This review article deals with biological background pertinent to the 'Cell Wall' experiment, the anticipated experimental procedures to be used, together with a perspective of how this space experiment will extend our knowledge in both pure and applied life sciences.
Resistance to the gravitational force is one of two major graviresponses in plants. However, only limited information has been obtained for its mechanism. The Resist Wall experiment aims to examine the role of the cortical microtubule-plasma membrane-cell wall continuum in gravity resistance, thereby clarifying its mechanism. For this purpose, we will cultivate Arabidopsis mutants defective in organization of cortical microtubules (tua6) or synthesis of membrane sterols (hmg1) as well as the wild type Columbia under microgravity and 1G conditions in the European Modular Cultivation System on the International Space Station up to reproductive stage, and compare phenotypes on growth and development using video images. These mutants are unable to form the normal cell wall and show disordered growth pattern on Earth. However, it is expected that the defects of such mutants are rescued and they can grow and develop more or less normally under microgravity in space, where formation of the tough cell wall is not required. We will also analyze changes in expression of genes involved in formation of the continuum and properties of related cellular components under microgravity conditions. The results of the Resist Wall experiment will clarify the molecular mechanism of gravity resistance and benefit efficient plant production not only in space but on Earth.
The European Modular Cultivation System (EMCS) installed within the US laboratory module, Destiny, and/or the European experiment module, Columbus, onboard the International Space Station (ISS), is an ESA facility available for plant research and biological experiments. The EMCS facility uses standard experiment containers (ECs) mounted on centrifuges and provides life support such as water and gas supply systems as well as observation systems. The experiment-specific hardware such as the plant cultivation chamber, root phototropism observation chamber, and plant root gravitropism observation chamber is integrated into the EC. JAXA has five themes concerning space plant research, of which two-Cell Wall and Resist Wall-will include conducting space experiments using the EMCS facility; according to the present shuttle flight schedule, they are due to be launched in mid February 2007. The objectives of the Cell Wall / Resist Wall experiment include in-orbit growth of 10-cm-long inflorescence stems of Arabidopsis and subsequent, post-flight morphology, biological, gene expression, and cell-wall properties analyses on the ground. In this article, we describe the EMCS facility, the plant cultivation and onboard chemical fixation system. Furthermore, we also discuss the verification experiments conducted by JAXA.
TANPOPO, dandelion, is the name of a grass whose seeds with floss are spread by the wind. We propose the analyses of interplanetary migration of microbes, organic compounds and meteoroids on ISS-JEM. Ultra low density aerogel will be used to capture micrometeoroid and debris. Particles captured by aerogel will be used for several analyses after the initial inspection of the gel and tracks. Careful analysis of the tracks in the aerogel will provide the size and velocity dependence of debris flux. The particles will be analyzed for mineralogical, organic and microbiological characteristics. To test the survival of microbes in space environment, microbial cells will be exposed. Organic compounds are also exposed to evaluate the possible denaturation under the conditions. Aerogels are ready for production in Japan. Aerogels and trays are space proven. All the analytical techniques are ready.
Nearly 50 multicelluar animal species have ever been flown on the near earth orbit or further. Animals used in space experiments range from Primates to Cnidaria. Widely used laboratory animals on the ground, such as rats and fruit flies, are frequently flown species. Mice, however, seem less popular in space experiments, probably because of their relatively poor resistance to the stressful space environment. To keep rodents onboard the space craft in a health state requires tremendous efforts. Moreover, the use of rodents onboard the International Space Station (ISS) has become extremely difficult, due to the cancellation of the Centrifuge facility. Rearing fish in space, on the other hand, is easier than to keep rodents, since their waste excretions are borne by the water flow and can be effectively removed by filtering. Fish are suitable model for the studies on development, radiation effects and vestibular functions. Among fish, Medaka (Oryzias latipes) will be the most useful species for space experiments, with the inventory of inbred and mutant strains, their genome sequence data, and the established gene knockout technologies. Medaka together with established small laboratory animals, such as C. elegans, are most promising species for the experiments onboard the ISS. Other unique groups of animals in space experiment are those inhabit in the arid area. These animals, such as Mongolian Gerbil (Meriones unguiculatus), generally require few drinking water and produce little amount of waste. This enables flight hardware being simpler. Although the lack of their genome sequence data is a big drawback, they are useful for space experiments, especially for those utilizing recoverable capsule satellites.