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第37回宇宙環境利用シンポジウム (2023年1月17日-18日. オンライン開催), Space Utilization Research (January 17-18, 2023. Online Meeting), 著者人数: 22名ほか, 資料番号: SA6000180007, G-1

Heavy-ion beams have been widely utilized as a novel and effective mutagen for mutation breeding in diverse species, including algae, but a preferred mutant cannot be easily obtained without a suitable large-scale screening method. We devised a unique, convenient, and effective method for screening mutants of Haematococcus pluvialis to isolate a strain resistant to environmental stress with low white fluorescence, i.e., a robust strain. Haematococcus was irradiated with heavy-ion beams of carbon ions, argon ions, and iron ions at various doses, after which approximately 10,000 surviving colonies were inoculated into 96-well plates, cultured for approximately 2 weeks, and then left to dry in a refrigerator for 3–12 months without a lid. In these unattended 96-well plates, cells in approximately one-third of the wells died and became white, and the remaining wells were approximately evenly split between red and green. The robustness of wild-type and mutant strains isolated from red and green wells was compared under severe environmental-stress conditions (125 µmol photons m−2 s−1, continuous light period, 45 mM sodium acetate). In the wild-type strain, most cells died, and 93.9% of cells emitted white autofluorescence. In contrast, few G4 cells emitted white autofluorescence, indicating a survival rate of 91.8%. Strains with excellent carotenoid production, such as G7 and R1, showed greater robustness compared to wild-type strains.

The evolution of dioecy from hermaphroditism allows for avoidance of self-pollination, and its evolutionary background has been investigated both experimentally and theoretically since it was first proposed by Darwin. To reproduce this evolution, we screened hermaphroditic mutants of Silene latifolia using heavy-ion beam or γ-ray irradiation and characterized the phenotypes of their floral organs. Our scatterplots indicate severe deviations from the trade-off relationships between pollen and ovule numbers and between seed and germinated pollen numbers in hermaphroditic mutant S. latifolia. These deviations presumably led to promotion of dioecy from the ancestral state of S. latifolia. To infer the likely flower phenotypic characteristics of the ancestral plant of S. latifolia before evolving dioecy, the flowers of Silene viscosa, a naturally hermaphroditic plant related to S. latifolia were also characterized. S. viscosa exhibits both spatial separation of stamens from pistils within the flower (reverse herkogamy) and temporal separation of stamen and pistil maturation (dichogamy), raising the question of whether hermaphroditic mutant S. latifolia, which is thought to be the ancestral state, would possess these functions. We show that two hermaphroditic mutants of the dioecious plant S. latifolia exhibit signs of protogyny (reverse dichogamy) and approach herkogamy, as pistils were constantly longer than stamens. These findings illustrate the evolution of dioecy from hermaphroditism as a self-pollination avoidance mechanism and to balance the investments into male and female functions.

第36回宇宙環境利用シンポジウム (2022年1月18日-19日. オンライン開催), Space Utilization Research (January 18-19, 2022. Online Meeting), 著者人数: 11名ほか, 資料番号: SA6000168003, G-02

第36回宇宙環境利用シンポジウム (2022年1月18日-19日. オンライン開催), Space Utilization Research (January 18-19, 2022. Online Meeting), 著者人数: 23名ほか, 資料番号: SA6000168002, G-01

We have developed a unique technology for mutation induction of plants using energetic ion beams at the RI Beam Factory (RIBF) of Rikagaku Kenkyūjo (RIKEN) (Institute of Physical and Chemical Research). Ion beams effectively induce mutations at relatively low doses without severely inhibiting growth. The irradiation treatment can be given to various plant materials and mutation can be induced in a short time, between seconds and a few minutes. The linear energy transfer (LET) of ions depends on the nuclide and velocity. Since LET value affects the mutation frequency, it is an important parameter to determine the most effective irradiation condition in mutagenesis. We determined the most effective dose in each LET for mutation induction in imbibed rice seeds. Subsequently, we analysed the mutated DNA responsible for the phenotype in morphological mutants. Most of the mutations were small deletions of less than 100 bp. Irradiations of C-ions and Ne-ions are effective for plant breeding because of the very high mutation rate and sufficient energy to disrupt a single gene. On the other hand, all mutations induced by Ar-ion (290 keV/μm) irradiation were large deletions ranging from 176 bp to approximately 620 kb. The average number of mutations in the target exon regions was 7.3, 8.5 and 4.3 per M3 mutant plant in C-ions, Ne-ions and Ar-ions, respectively. The number of mutations induced by heavy-ion irradiation was relatively small. We could identify six responsible genes for eight mutants induced by C-ion and Ne-ion irradiations and two responsible genes for four mutants induced by Ar-ion irradiation. Three of these were genes not previously described.

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第34回宇宙環境利用シンポジウム (2020年1月21日-22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, Space Utilization Research (January 21-22, 2020. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 著者人数: 28名ほか, 資料番号: SA6000145010, G-02

第20回宇宙科学シンポジウム (2020年1月8日-9日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 20th Space Science Symposium (January 8-9, 2020. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 著者人数: 18名, 資料番号: SA6000152073, レポート番号: P1.47

第20回宇宙科学シンポジウム (2020年1月8日-9日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 20th Space Science Symposium (January 8-9, 2020. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000152075, レポート番号: P1.49

Argon-ion beam is an effective mutagen capable of inducing a variety of mutation types. In this study, an argon ion-induced pale green mutant of was isolated and characterized. The mutant, designated Ar50-33-pg1, exhibited moderate defects of growth and greening and exhibited rapid chlorosis in photosynthetic tissues. Fluorescence microscopy confirmed that mesophyll chloroplasts underwent substantial shrinkage during the chlorotic process. Genetic and whole-genome resequencing analyses revealed that Ar50-33-pg1 contained a large 940 kb deletion in chromosome V that encompassed more than 100 annotated genes, including 41 protein-coding genes such as /, , and . One of the deleted genes, , for a thylakoid membrane-localized metalloprotease, was the major contributory gene responsible for the pale mutant phenotype. Both an mutant and F progeny of an Ar50-33-pg1 × cross-exhibited chlorotic phenotypes similar to those of Ar50-33-pg1. Furthermore, ultrastructural analysis of mesophyll cells revealed that Ar50-33-pg1 and initially developed wild type-like chloroplasts, but these were rapidly disassembled, resulting in thylakoid disorganization and fragmentation, as well as plastoglobule accumulation, as terminal phenotypes. Together, these data support the utility of heavy-ion mutagenesis for plant genetic analysis and highlight the importance of in the structural maintenance of grana in mesophyll chloroplasts.

Purpose: To assess the unique biological effects of different forms of ionizing radiation causing DNA double-strand breaks (DSBs), we compared the killing effect, mutagenesis frequency, and mutation type spectrum using the model filamentous fungus Neurospora. Materials and methods: Asexual spores of wild-type Neurospora and two DSB repair-deficient strains [one homologous recombination- and the other non-homologous end-joining (NHEJ) pathway-deficient] were irradiated with argon (Ar)-ion beams, ferrous (Fe)-ion beams, or X-rays. Relative biological effectiveness (RBE), forward mutation frequencies at the ad-3 loci, and mutation spectra at the ad-3B gene were determined. Results: The canonical NHEJ (cNHEJ)-deficient strain showed resistance to higher X-ray doses, while other strains showed dose-dependent sensitivity. In contrast, the killing effects of Ar-ion and Fe-ion beam irradiation were dose-dependent in all strains tested. The rank order of RBE was Ar-ion > Fe-ion > C-ion. Deletion mutations were the most common, but deletion size incremented with the increasing value of linear energy transfer (LET). Conclusions: We found marked differences in killing effect of a cNHEJ-deficient mutant between X-ray and high-LET ion beam irradiations (Ar and Fe). The mutation spectra also differed between irradiation types. These differences may be due to the physical properties of each radiation and the repair mechanism of induced damage in Neurospora crassa. These results may guide the choice of irradiation beam to kill or mutagenize fungi for agricultural applications or further research.

第18回宇宙科学シンポジウム (2018年1月9日-10日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 18th Space Science Symposium (January 9-10, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000118051, レポート番号: P-017

In Sayaka Murata's novel Convenience Store Woman, the heroine, Keiko Furukura, is a woman chained by the three shackles of being a virgin, unmarried and a part-time worker. To Furukura, the convenience store is a holy place that enables her function as a "normal part of society". There are various kinds of sounds in the store such as music. However, her encounter with Shiraha causes discord and her belief in the convenience store is shaken. Led by a "heavenly voice" in the convenience store, her conscience is awakened just as she quits the job and is about to surrender to society. She turns down a proposal from Shiraha and becomes a convenience store woman in a true sense. This novel expresses the author's reflection on rebellion against modern society and the concern of humanity with a sense of humor.

第17回宇宙科学シンポジウム (2017年1月5日-6日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 17th Space Science Symposium (January 5-6, 2017. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000060155, レポート番号: P-113

RIKEN RI Beam Factory is one of the world-leading heavy-ion facilities where nuclear physics research and application research have been conducted. One important application, performed more than twenty years at RIBF, is breeding plants and others where energetic heavy ions are used as very effective mutagens. Our previous main accelerator RIKEN Ring Cyclotron has been used for this purpose but available beam energies and resultant ion ranges are limited for medium heavy ions such as argon and iron ions. Hence, a new beam transport line delivering beams accelerated by one of our new-generation cyclotrons, RIKEN Intermediate Ring Cyclotron, to E5H experimental vault, where biological samples are irradiated in air, has been constructed. We will report design of the new beam line and the results obtained by the beam-commissioning test performed using a 160 MeV/nucleon argon beam in January 2015. We obtained performances as designed, for example, nearly 100% transmission efficiency, and a threefold increase of ion ranges. The higher-energy argon beam delivered by the new beam line was used to induce seaweed mutations immediately after the beam test., Proceedings of the 13th Heavy Ion Accelerator Technology Conference, HIAT2015, Yokohama, Japan

第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 16th Space Science Symposium (January 6-7, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000046041, レポート番号: P-042

著者人数: 16名, Accepted: 2010-11-20, 資料番号: SA1002792000

We previously used heavy-ion beam irradiation to generate a self-incompatible mutant of Verbena×hybrida ‘Temari Coral Pink’ (SC), which exhibits a late-acting self-incompatibility system. In the present study, the behavior of pollen tubes and seed productivity after self-pollination were comparatively investigated in SC and wild species Verbena peruviana (VP), one of the parental species of Verbena×hybrida. Although reciprocal cross-pollination between VP and SC produced seeds with high frequencies, namely 57.1% for SC×VP and 59.7% for VP×SC, self-pollinated VP flowers produced no seeds. In the latter, almost all of the pollen germinated on the stigma, but further growth of the pollen tube was inhibited at the upper part of the style. These observations of pollen tube behavior may indicate that the SI system of VP was different from that of SC. VP may possess a homomorphic gametophytic SI system, which is characterized by the inhibition of pollen tube growth at style. We propose a set of SC and VP as a novel model plants for genetic analysis of the SI mechanism in the Verbenaceae family.

A poly (3-hydroxybutyrate) (PHB) depolymerase was purified 4, 400-fold from the supernatant fraction of Ralstonia eutropha cells through fractionation with ammonium sulfate and chromatography with Toyopearl DEAE, Q Sepharose, and Toyopearl Ether. The partially purified preparation showed a high level of specific activity to hydrolyze amorphous PHB, comparable to PhaZd from R. eutropha. The degradation was inhibited by diisopropylphosphate (10mM) and dithiothreitol (100mM). Most of the degradation products were 3-hydroxybutyrate oligomers. The properties of the enzyme closely resembled those of PhaZd, but some differences were observed. This distinction from PhaZd was discussed.

The original publication is available at www.springerlink.com.

第15回宇宙科学シンポジウム (2015年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 15th Space Science Symposium (January 6-7, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000034241, レポート番号: P-242

Ralstonia eutropha H16 mobilizes intracellularly accumulated poly(3-hydroxybutyrate) with intracellular poly(3-hydroxybutyrate) depolymerases. Different types of depolymerase, PhaZ1 and its homologs, account for the mobilization significantly but incompletely, and it is proposed that further unknown depolymerases or related enzymes complement the mobilization. A novel hydrolase was therefore investigated. The amino acid sequence of the intracellular 3HB-oligomer hydrolase of Acidovoraxsp. SA1 and the genome sequence of Ralstonia solanacearum, a close relative of R. eutropha, revealed a candidate for the hydrolase gene. The DNA sequence of its hydrolase was used for the design of a pair of primes. With chromosomal DNA of R. eutropha as a template, these primers were used to amplify about a 1.3-kbp fragment including the equivalent gene, phaZc. Then the phaZc gene was cloned by Southern hybridization using the amplified DNA fragment as a probe. The hydrolase (PhaZc) was purified from Escherichia coli overexpressing phaZc and characterized. Immunoblot analysis revealed that PhaZc exists mainly in the cytosolic fraction of R. eutropha. PhaZc degraded various 3-hydroxybutyrate-oligomers at a high rate and artificial amorphous poly (3-hydroxybutyrate) at a lower rate. A phaZ-rmLl mutation enhanced the deposition of PHB in the logarithmic phase in a nutrient-rich medium. PhaZc differs from the previously reported hydrolases in R. eutropha and is a novel type of intracellular 3HB-oligomer hydrolase, which participates in the mobilization of PHB along with other hydrolases.

The different forms of flowers in a species have attracted the attention of many evolutionary biologists, including Charles Darwin. In Fagopyrum esculentum (common buckwheat), the occurrence of dimorphic flowers, namely short-styled and long-styled flowers, is associated with a type of self-incompatibility (SI) called heteromorphic SI. The floral morphology and intra-morph incompatibility are both determined by a single genetic locus named the S-locus. Plants with short-styled flowers are heterozygous (S/s) and plants with long-styled flowers are homozygous recessive (s/s) at the S-locus. Despite recent progress in our understanding of the molecular basis of flower development and plant SI systems, the molecular mechanisms underlying heteromorphic SI remain unresolved. By examining differentially expressed genes from the styles of the two floral morphs, we identified a gene that is expressed only in short-styled plants. The novel gene identified was completely linked to the S-locus in a linkage analysis of 1,373 plants and had homology to EARLY FLOWERING 3. We named this gene S-LOCUS EARLY FLOWERING 3 (S-ELF3). In an ion-beam-induced mutant that harbored a deletion in the genomic region spanning S-ELF3, a phenotype shift from short-styled flowers to long-styled flowers was observed. Furthermore, S-ELF3 was present in the genome of short-styled plants and absent from that of long-styled plants both in world-wide landraces of buckwheat and in two distantly related Fagopyrum species that exhibit heteromorphic SI. Moreover, independent disruptions of S-ELF3 were detected in a recently emerged self-compatible Fagopyrum species and a self-compatible line of buckwheat. The nonessential role of S-ELF3 in the survival of individuals and the prolonged evolutionary presence only in the genomes of short-styled plants exhibiting heteromorphic SI suggests that S-ELF3 is a suitable candidate gene for the control of the short-styled phenotype of buckwheat plants.

A simple amphiphilic low-molecular-weight gelator based on L -lysine, N α -acetyl- N e -lauroyl- L -lysine ( 1 ), its alkali metal salts [Na ( 2 ) and K ( 3 )], and two-component gelators [ 1 and 2 and 1 and 3 ] were synthesized. Compound 1 had a good hydrogelation ability that formed a pure water gel at 2 g L −1 (0.2 wt.%) and a saline gel at 4 g L −1 (0.4 wt.%). Two-component compounds were able to form hydrogels in aqueous solutions containing alkali metal and alkali earth metal ions in addition to pure water and saline. Although 1 formed organogels in a few organic solvents, two-component compounds also functioned as a good organogelator. The FT-IR study indicated that the driving forces for the formation of supramolecular gels were hydrogen-bonding and hydrophobic interactions. Furthermore, the thermal properties of the hydrogels are discussed.

The electrical, optical and structural properties of Al0.5In0.5P and Ga0.5In0.5P layers grown on (001) GaAs substrates by gas source molecular beam epitaxy (GSMBE) using phosphine (PH3) gas have been studied. For heavy Be doping, the electrical activity was found to be unity up to atomic Be concentration of 2 × 1018 cm-3 in Al0.5In0.5P and 3 × 1019 cm-3 in Ga0.5In0.5P. The maximum hole concentrations achieved are 3.5 × 1018 cm-3 in Al0.5In0.5P and 4 × 1019 cm-3 in Ga0.5In0.5P. 20 K photoluminescence (PL) measurements for heavily Be-doped Al0.5In0.5P showed that the decrease in electrical activity is due to deep levels resulting possibly from Al-Be related defects. An ordered structure and a compositional modulated structure were first observed in Ga0.5In0.5P grown by GSMBE. The degree of ordering was found to be less perfect than that for metalorganic vapor phase epitaxy (MOVPE) due to the lower growth temperature. Typical 300 K PL energy was found to be 1.88 eV which was 20 meV lower than the “normal” energy (1.9 eV).

36, KJ00004196386, 資料

2019年度

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