髙橋 秀幸

Green plants produce carbohydrate as an energy for all organisms by photosynthesis. It is therefore considered that plant cultivation is necessary for life support not only on Earth but also in space. To inhabit the space for a long duration, human needs to be closed in the life support system in which plants provide them with foods and a stress-relief circumstance. During evolution, on the other hand, plants developed various strategies to survive terrestrial environment on Earth because of their sessile nature. Plant responses to gravity and lights are examples of such strategy to avoid or mitigate stressful environment they come across. Now, space environment is available for biological studies to understand how plants respond to gravity and how plants are influenced by microgravity and/or space radiation. We extend such studies to understand the effects of space environment on plant growth and development in the seed-to-seed or the generation-to-generation experiments. To explore the deeper space or inhabit planets such as the moon or Mars, we next need to establish a sustainable recycling-oriented life support system with plant cultivation and environmental control facilities. Here, we show our research scenario of the space-utilizing plant science to achieve such objective, which is important to efficiently cultivate plants and develop the life support system in space. We believe our approach, in cooperation with various communities of the related fields, enables us to further reveal the biological systems required for not only colonizing to space but also conserving or improving the living Earth.

第29回宇宙環境利用シンポジウム (2015年1月24日-25日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000035014

Roots show tropisms in response to environmental cues such as gravity, light, moisture gradient. Each tropism is affected by the other stimulations. For instance, graviresponse interferes root hydrotropism and phototropism. We have identified MIZ1 gene as a regulator of hydrotropism. However, regulation and function of MIZ1 have been unknown. Here, we showed that light and ABA signal affect hydrotropism via modulation of MIZ1 expression. We found that hydrotropism was reduced in dark-grown roots when compared with light-grown ones. In addition, we found that light signal was necessary for MIZ1-GFP expression at the root cap. Moreover, both of hydrotropism and MIZ1 expression are decreased in hy5 mutant. Because HY5 regulates light-dependent transcription, the result suggests that HY5-dependent light signaling is required for expression of MIZ1 and thus for appropriate hydrotropic response. It is also known that HY5 is involved in ABA signaling, and that ABA is an important player for hydrotropism. To assess the possibility that HY5 also regulates ABA-mediated MIZ1 expression, we analyzed MIZ1-GFP level in ABA-treated hy5 roots. The result shows that ABA could recover MIZ1-GFP level similar to that of WT. Moreover, ABA-treated hy5 showed normal hydrotropic response as did ABA-treated WT. These results suggest that HY5 is not involved in ABA-dependent regulation of hydrotropism which acts even in darkness. These machineries may profit for plants to acquire water adequately.

第26回宇宙利用シンポジウム(2010年1月25日-26日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス)形態: カラー図版あり共催: 日本学術会議著者人数: 16人資料番号: AA0064730062

第25回宇宙利用シンポジウム(2009年1月14日-15日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス)資料番号: AA0064297012

第25回宇宙利用シンポジウム(2009年1月14日-15日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス)形態: カラー図版あり資料番号: AA0064297011

When cucumber seeds are placed in a horizontal position for germination, the resulting seedlings develop a protuberance called peg on the lower side of the transition zone between hypocotyl and root. Peg formation is suppressed on the upper side of the gravistimulated transition zone. We have shown that auxin plays an essential role in the lateral placement of a peg. That is, auxin level was significantly reduced in the upper side of the gravistimulated transition zone, and application of exogenous auxin caused a peg formation on both sides. On the other hand, treatment of seedlings with inhibitors of auxin efflux resulted in development of a peg on both upper and lower sides of the transition zone. Thus, active efflux of auxin might occur on the upper side of the gravistimulated transition zone for reducing auxin level and thereby suppressing peg formation. To develop a model for testing this hypothesis, we isolated cDNAs encoding auxin efflux carriers from cucumber and analyzed their expressions. Also, we examined a possible involvement of differential regulation of auxin-mediated transcription in peg formation. In addition, we have investigated other gravity-dependent phenomena: hydrotropism and its interference by gravitropism in roots, and gravity-dependency of circumnutation and lateral bud outgrowth. These experimental systems provide us with clues to understand the regulatory mechanisms of plant gravimorphogenesis by auxin.

資料番号: AA0063706115

資料番号: AA0063349105

第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京)共催: 日本学術会議著者人数: 13人資料番号: AA0064113098

第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京)共催: 日本学術会議著者人数: 15人資料番号: AA0064113101

第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京)共催: 日本学術会議著者人数: 16人資料番号: AA0064113095