A relationship between lignin formation and gravity is important in biological development of plants in space, because lignin is considered to have played one of the most important roles in the evolution of land plants. This relationship has been studied from a basic biological point of view in herbaceous plants. On the other hand, this relationship is mainly focused on formation of reaction wood in woody plants and has been studied from a practical point of view because of deleterious features of reaction wood for wood manufacture. The International Space Station (ISS) is currently in operation and unique space experiments are to be performed using both herbaceous and woody plants. Recent advances in the study of roles of gravity on lignin and secondary wall formation are reviewed.

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We have started a space experiment using an experimental organism, the nematode Caenorhabditis elegans, in the Japanese Experiment Module, KIBO, of the International Space Station (ISS). The specimens were boarded by space shuttle Atlantis on mission STS-129 which launched from NASA Kennedy Space Center on November 16, 2009. The purpose of the experiment was several-fold: (i) to verify the efficacy of RNA interference (RNAi) in space, (ii) to monitor transcriptional and post-translational alterations in the entire genome in space, and (iii) to investigate mechanisms regulating and countermeasures for muscle alterations in response to the space environment. In particular, this will be the first study to utilize RNAi in space.

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Skeletal muscle atrophy is an often-unavoidable response to a prolonged lack of muscle use or spaceflight (referred to as "unloading"), and presents a particular challenge for astronauts during spaceflight. An increased understanding of the molecular mechanisms of muscle atrophy may lead to the development of effective therapies to combat this widespread condition. In this project, we aim to elucidate the molecular mechanisms of microgravity-induced skeletal muscle atrophy, especially physiological relevance of Cbl-b ubiquitin ligase. Japanese experimental module (JEM), "Kibo", in International Space Station has been constructed until June, 2009. This enables us to perform cell culture experiment, which is an easy system to observe direct effects of microgravity on the cell, in space for a long term. This project is called "Myo Lab", which means "Laboratory for Skeletal Muscle". This decal images our dream (space shuttle) that flight beyond Earth forward to "Kibo". In addition, the flame from shuttle means skeletal muscle.

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Ionizing radiation-induced bystander effect is the phenomenon whereby cells that are not themselves irradiated but received signals from directly irradiated cells exhibit biological responses. Human exposure to heavy-ion radiation occurs during manned space missions at the dose and dose rate much lower than those for cancer therapy. It should be noted herein that less irradiated cells coexist with more non-irradiated counterparts in a cell population exposed to a lower dose of radiation whose linear energy transfer is higher. The bystander effect should be thence examined to decipher the action mechanism of low-dose heavy ions. The bystander effect of heavy ions is manifested as inactivated clonogenic potential, a transient apoptotic response, delayed p53 phosphorylation, gene expression changes, a transient cell-cycle arrest, chromosome aberrations, elevated mutation frequency and micronucleation. Proposed underpinning mechanisms involve gap junctional intercellular communication and reactive oxygen/nitrogen species. This paper reviews briefly the current knowledge of the heavy ion-induced bystander effect.

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The growth of terrestrial cyanobacterium, Nostoc sp., on the Martian Regolith Simulant (MRS) and its vacuum tolerance were examined in relevance of our challenges to inhabit Mars. The viability of the cyanobacteria was evaluated by microscopic observation after staining by fluorescein diacetate (FDA). The general terrestrial cyanobacterial lump collected from the ground showed a significantly high tolerance against exposure to high vacuum environment for more than one year. To elucidate its high tolerance function scientifically, Nostoc sp. HK-01 was used as another material for this study. After two weeks exposure to high vacuum environment (10^-5 Pa), Nostoc sp. HK-01 start to grow again in a liquid culture medium. The A'MED (Arai's Mars Ecosystem Dome) is designed to be installed on Mars for agricultural production. A'MED was found useful to conduct our study. Nostoc sp. HK-01 grew for over 140 days, and chlorophyll synthesis was normal on the MRS. These results verify the possible adaptation of cyanobacteria, and growth under the low atmospheric pressure environment on Mars.

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It is known that the teleost scale regenerates after being removed. We previously reported that the osteogenesis in regenerating scales was very similar to that in calvarial bone, which suggests that regenerating scale can be used as a model for osteogenesis to analyze the interaction between osteoblasts and osteoclasts. In the present study, we developed an assay system using regenerating scales by modifying our assay system with normal scales. The weight of one regenerating scale cannot be measured precisely because the rate of calcification in regenerating scales is lower than that in normal scales. In regenerating scales, thus, the respective marker enzyme activity, i.e., alkaline phosphatase (ALP) for osteoblasts and tartrate-resistant acid phosphatase (TRAP) for osteoclasts, was normalized by the surface area (mm²) of each goldfish scale. With this modified method, we were able to detect ALP and TRAP activities with no variation in the lines of regenerating scales. In addition, we found that the ALP activity in the regenerating scales significantly increased under 3G acceleration loading by vibration, while the TRAP activity in the loaded regenerating scales significantly decreased. We strongly believe that the regenerating scale is a good material for the analysis of bone metabolism under different gravity environments.

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