研究者詳細 - 西村　和紗

A low-cost dpMIG-seq method for elucidating complex inheritance in polysomic crops: A case study in tetraploid blueberry 査読

Anekomochi glutinous rice provides low postprandial glycemic response by enhanced insulin action via GLP-1 release and vagal afferents activation 査読

Kento Ohbayashi, Yudai Sugiyama, Taichi Nohmi, Kazusa Nishimura, Tetsuya Nakazaki, Yo-Ichiro Sato, Takehiro Masumura, Yusaku Iwasaki

The Journal of Physiological Sciences 74 47 2024年9月

Kyoka Nagasaka, Kazusa Nishimura, Ko Motoki, Keigo Yamagata, Soichiro Nishiyama, Hisayo Yamane, Ryutaro Tao, Ryohei Nakano, Tetsuya Nakazaki

Horticulture Research uhae248 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Oxford University Press (OUP)

Abstract

Next-generation sequencing (NGS) library construction often requires high-quality DNA extraction, precise adjustment of DNA concentration, and restriction enzyme digestion to reduce genome complexity, which results in increased time and cost in sample preparation and processing. To address these challenges, a PCR-based method for rapid NGS library preparation, named dpMIG-seq, has been developed and proven effective for high-throughput genotyping. However, the application of dpMIG-seq has been limited to diploid and polyploid species with disomic inheritance. In this study, we obtained genome-wide single nucleotide polymorphism (SNP) markers for tetraploid blueberry to evaluate genotyping and downstream analysis outcomes. Comparison of genotyping qualities inferred across samples with different DNA concentrations and multiple bioinformatics approaches revealed high accuracy and reproducibility of dpMIG-seq-based genotyping, with Pearson’s correlation coefficients between replicates in the range of 0.91 to 0.98. Furthermore, we demonstrated that dpMIG-seq enables accurate genotyping of samples with low DNA concentrations. Subsequently, we applied dpMIG-seq to a tetraploid F1 population to examine the inheritance probability of parental alleles. Pairing configuration analysis supported the random meiotic pairing of homologous chromosomes on a genome-wide level. On the other hand, preferential pairing was observed on chr-11, suggesting that there may be an exception to the random pairing. Genotypic data suggested quadrivalent formation within the population, although the frequency of quadrivalent formation varied by chromosome and cultivar. Collectively, the results confirmed applicability of dpMIG-seq for allele dosage genotyping and are expected to catalyze the adoption of this cost-effective and rapid genotyping technology in polyploid studies.

DOI： 10.1093/hr/uhae248

Chromosome-level genome assemblies for two quinoa inbred lines from northern and southern highlands of Altiplano where quinoa originated 査読

Yasufumi Kobayashi, Hideki Hirakawa, Kenta Shirasawa, Kazusa Nishimura, Kenichiro Fujii, Rolando Oros, Giovanna R. Almanza, Yukari Nagatoshi, Yasuo Yasui, Yasunari Fujita

Frontiers in Plant Science 15 2024年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers Media SA

Quinoa is emerging as a key seed crop for global food security due to its ability to grow in marginal environments and its excellent nutritional properties. Because quinoa is partially allogamous, we have developed quinoa inbred lines necessary for molecular genetic analysis. Our comprehensive genomic analysis showed that the quinoa inbred lines fall into three genetic subpopulations: northern highland, southern highland, and lowland. Lowland and highland quinoa are the same species, but have very different genotypes and phenotypes. Lowland quinoa has relatively small grains and a darker grain color, and is widely tested and grown around the world. In contrast, the white, large-grained highland quinoa is grown in the Andean highlands, including the region where quinoa originated, and is exported worldwide as high-quality quinoa. Recently, we have shown that viral vectors can be used to regulate endogenous genes in quinoa, paving the way for functional genomics to reveal the diversity of quinoa. However, although a high-quality assembly has recently been reported for a lowland quinoa line, genomic resources of the quality required for functional genomics are not available for highland quinoa lines. Here we present high-quality chromosome-level genome assemblies for two highland inbred quinoa lines, J075 representing the northern highland line and J100 representing the southern highland line, using PacBio HiFi sequencing and dpMIG-seq. In addition, we demonstrate the importance of verifying and correcting reference-based scaffold assembly with other approaches such as linkage maps. The assembled genome sizes of J075 and J100 are 1.29 and 1.32 Gb, with contigs N50 of 66.3 and 12.6 Mb, and scaffold N50 of 71.2 and 70.6 Mb, respectively, comprising 18 pseudochromosomes. The repetitive sequences of J075 and J100 represent 72.6% and 71.5% of the genome, the majority of which are long terminal repeats, representing 44.0% and 42.7% of the genome, respectively. The de novo assembled genomes of J075 and J100 were predicted to contain 65,303 and 64,945 protein-coding genes, respectively. The high quality genomes of these highland quinoa lines will facilitate quinoa functional genomics research on quinoa and contribute to the identification of key genes involved in environmental adaptation and quinoa domestication.

DOI： 10.3389/fpls.2024.1434388

Workflow for development of CAPS markers with one type of restriction enzyme to identify citrus cultivars 査読

Kazusa Nishimura, Maho Okuma, Junko Kaneyoshi, Atsu Yamasaki, Kyoka Nagasaka, Kazuki Murata, Yuki Monden, Kenji Kato, Hidetaka Nishida, Tetsuya Nakazaki, Ryohei Nakano

Tree Genetics & Genomes 20 ( 5 ) 2024年8月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

Given the ease of propagating fruit tree species through cloning, the economic viability of their breeding programs hinges on protecting breeders' rights. This necessitates the development of highly accurate DNA markers for cultivar identification. Here, we present a methodology for the rapid design of cleaved amplified polymorphic sequence (CAPS) markers to discriminate newly bred Japanese citrus cultivars from genetically related cultivars. We first compared the performance of ddRAD-seq and MIG-seq in citrus germplasm. The ddRAD-seq libraries generated using EcoRI and HindIII restriction enzymes yielded the highest number of polymorphisms. Subsequently, ddRAD-seq with EcoRI and HindIII was employed to analyze 29 citrus cultivars and thus identify 331,801 genome-wide polymorphisms. A semi-automated bioinformatics pipeline was then utilized to identify candidate CAPS markers, resulting in the discovery of 14,072 potential markers. Of these candidates, 52 were chosen for validation based on their recognition by the PstI restriction enzyme. This evaluation resulted in the development of 11 highly discriminative CAPS markers. Remarkably, a combination of only six such markers was sufficient to differentiate newly bred cultivars from their genetically related parents. The single restriction enzyme employed for these markers facilitates straightforward multiplexing. Finally, a combination of one multiplex marker testing two loci and four singleplex markers was successfully selected that completely discriminated the cultivars other than the bud sports used in this study. The pipeline established here extends beyond citrus and has the potential to simplify marker development and cultivar protection in various plant species.

DOI： 10.1007/s11295-024-01661-x

Degenerate oligonucleotide primer MIG‐seq: an effective PCR‐based method for high‐throughput genotyping 査読

その他リンク： https://link.springer.com/article/10.1007/s11295-024-01661-x/fulltext.html

Kazusa Nishimura, Hiroyuki Kokaji, Ko Motoki, Akira Yamazaki, Kyoka Nagasaka, Takashi Mori, Rihito Takisawa, Yasuo Yasui, Takashi Kawai, Koichiro Ushijima, Masanori Yamasaki, Hiroki Saito, Ryohei Nakano, Tetsuya Nakazaki

The Plant Journal 2024年3月

担当区分：筆頭著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

SUMMARY

Next‐generation sequencing (NGS) library construction often involves using restriction enzymes to decrease genome complexity, enabling versatile polymorphism detection in plants. However, plant leaves frequently contain impurities, such as polyphenols, necessitating DNA purification before enzymatic reactions. To overcome this problem, we developed a PCR‐based method for expeditious NGS library preparation, offering flexibility in number of detected polymorphisms. By substituting a segment of the simple sequence repeat sequence in the MIG‐seq primer set (MIG‐seq being a PCR method enabling library construction with low‐quality DNA) with degenerate oligonucleotides, we introduced variability in detectable polymorphisms across various crops. This innovation, named degenerate oligonucleotide primer MIG‐seq (dpMIG‐seq), enabled a streamlined protocol for constructing dpMIG‐seq libraries from unpurified DNA, which was implemented stably in several crop species, including fruit trees. Furthermore, dpMIG‐seq facilitated efficient lineage selection in wheat and enabled linkage map construction and quantitative trait loci analysis in tomato, rice, and soybean without necessitating DNA concentration adjustments. These findings underscore the potential of the dpMIG‐seq protocol for advancing genetic analyses across diverse plant species.

DOI： 10.1111/tpj.16708

Pollen Dispersion is a Key Factor for Autonomous Fruit Set Under High Temperatures in the Capsicum annuum ‘Takanotsume’ 査読

Introduction of a diverse genetic background of Pyrus into Malus through intergeneric hybridization. 査読

Takuya Morimoto, Ryuya Narazaki, Hiroaki Okabe, Lumin Zhang, Kazusa Nishimura, Akihiro Itai

Molecular Genetics and Genomics 299 21 2024年3月

Akira Yamazaki, Ao Takezawa, Kazusa Nishimura, Ko Motoki, Kyoka Nagasaka, Ryohei Nakano, Tetsuya Nakazaki, Munetaka Hosokawa

The Horticulture Journal QH-094 2023年10月

Genome sequencing reveals the genetic architecture of heterostyly and domestication history of common buckwheat. 査読国際誌

Jeffrey A Fawcett, Ryoma Takeshima, Shinji Kikuchi, Euki Yazaki, Tomoyuki Katsube-Tanaka, Yumei Dong, Meifang Li, Harriet V Hunt, Martin K Jones, Diane L Lister, Takanori Ohsako, Eri Ogiso-Tanaka, Kenichiro Fujii, Takashi Hara, Katsuhiro Matsui, Nobuyuki Mizuno, Kazusa Nishimura, Tetsuya Nakazaki, Hiroki Saito, Naoko Takeuchi, Mariko Ueno, Daiki Matsumoto, Miyu Norizuki, Kenta Shirasawa, Chengyun Li, Hideki Hirakawa, Tatsuya Ota, Yasuo Yasui

Nature plants 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

Common buckwheat, Fagopyrum esculentum, is an orphan crop domesticated in southwest China that exhibits heterostylous self-incompatibility. Here we present chromosome-scale assemblies of a self-compatible F. esculentum accession and a self-compatible wild relative, Fagopyrum homotropicum, together with the resequencing of 104 wild and cultivated F. esculentum accessions. Using these genomic data, we report the roles of transposable elements and whole-genome duplications in the evolution of Fagopyrum. In addition, we show that (1) the breakdown of heterostyly occurs through the disruption of a hemizygous gene jointly regulating the style length and female compatibility and (2) southeast Tibet was involved in common buckwheat domestication. Moreover, we obtained mutants conferring the waxy phenotype for the first time in buckwheat. These findings demonstrate the utility of our F. esculentum assembly as a reference genome and promise to accelerate buckwheat research and breeding.

DOI： 10.1038/s41477-023-01474-1

A simple method for measuring pollen germination rate using machine learning 査読

Akira Yamazaki, Ao Takezawa, Kyoka Nagasaka, Ko Motoki, Kazusa Nishimura, Ryohei Nakano, Tetsuya Nakazaki

Plant Reproduction 36 ( 4 ) 355 - 364 2023年6月

Indicator Candidate Traits for Autonomous Fruit Set Ability Under High Temperatures in Capsicum 査読

Akira Yamazaki, Ao Takezawa, Ryohei Nakano, Kazusa Nishimura, Ko Motoki, Munetaka Hosokawa, Tetsuya Nakazaki

Journal of Horticultural Research 30 ( 2 ) 105 - 116 2023年1月

掲載種別：研究論文（学術雑誌）出版者・発行元：Walter de Gruyter GmbH

Abstract

“Autonomous fruit set” refers to self-pollination and fruit set without pollen vectors such as vibration or insects. Autonomous fruit set under high-temperature stress is an important breeding goal as climate change can reduce fruit yields in Capsicum. We screened Capsicum cultivars for autonomous fruit set ability in a greenhouse environment and investigated pollen germination, viability, pollen grains number, chlorophyll fluorescence (Fv/Fm), style length, anther cone length, and anthesis stage under high temperatures in order to identify indicator traits for screening more genotypes with autonomous fruit set ability. The fruit set of the ‘Takanotsume’ (57.7 ± 20.6%) and ‘Goshiki Kyokko’ (52.2 ± 14.2%) cultivars (both C. annuum) were higher than those of other cultivars. Correlation analysis showed that pollen germination had the highest correlation with fruit set in C. annuum cultivars (r = 0.63). These results indicate that ‘Takanotsume’ and ‘Goshiki Kyokko’ are useful cultivars for novel breeding programs focusing on autonomous fruit sets under high temperatures, and pollen germination in C. annuum was a convincing candidate for an indicator trait of autonomous fruit set ability under high temperatures.

DOI： 10.2478/johr-2022-0017

Analysis of mechanism regulating high total soluble solid content in the parthenocarpic tomato fruit induced by pat-k gene 査読

Chiaki Fukudome, Rihito Takisawa, Ryohei Nakano, Miyako Kusano, Makoto Kobayashi, Ko Motoki, Kazusa Nishimura, Tetsuya Nakazaki

Scientia Horticulturae 301 111070 - 111070 2022年7月

MIG-seq is an effective method for high-throughput genotyping in wheat (Triticum spp.) 査読国際誌

Kazusa Nishimura, Ko Motoki, Akira Yamazaki, Rihito Takisawa, Yasuo Yasui, Takashi Kawai, Koichiro Ushijima, Ryohei Nakano, Tetsuya Nakazaki

DNA Research 29 ( 2 ) 2022年4月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Oxford University Press (OUP)

Abstract

MIG-seq (Multiplexed inter-simple sequence repeats genotyping by sequencing) has been developed as a low cost genotyping technology, although the number of polymorphisms obtained is assumed to be minimal, resulting in the low application of this technique to analyses of agricultural plants. We applied MIG-seq to 12 plant species that include various crops and investigated the relationship between genome size and the number of bases that can be stably sequenced. The genome size and the number of loci, which can be sequenced by MIG-seq, are positively correlated. This is due to the linkage between genome size and the number of simple sequence repeats (SSRs) through the genome. The applicability of MIG-seq to population structure analysis, linkage mapping, and quantitative trait loci (QTL) analysis in wheat, which has a relatively large genome, was further evaluated. The results of population structure analysis for tetraploid wheat showed the differences among collection sites and subspecies, which agreed with previous findings. Additionally, in wheat biparental mapping populations, over 3,000 SNPs/indels with low deficiency were detected using MIG-seq, and the QTL analysis was able to detect recognized flowering-related genes. These results revealed the effectiveness of MIG-seq for genomic analysis of agricultural plants with large genomes, including wheat.

DOI： 10.1093/dnares/dsac011

その他リンク： https://academic.oup.com/dnaresearch/article-pdf/29/2/dsac011/43439343/dsac011.pdf

Geographical distribution and adaptive variation of VRN-A3 alleles in worldwide polyploid wheat (Triticum spp.) species collection 査読国際誌

Nishimura, K, H. Handa, N. Mori, K. Kawaura, A. Kitajima, T, Nakazaki

Planta 256 ( 6 ) 132 - 132 2021年5月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

MAIN CONCLUSION: The distribution of early flowering alleles of VRN-A3 was found to be biased to low latitudes, and these alleles may contribute to environmental adaptability to low latitudes in cultivated emmer wheat. In wheat (Triticum spp.), the flowering time is an important trait for successful seed production and yield by adapting to the regional environment. An early flowering allele of VRN-A3 with 7- and 25-bp insertions in the promoter region (Vrn-A3a-h1) has recently been reported from the analysis of an emmer wheat (Triticum turgidum L. ssp. dicoccum) accession, TN26. This early flowering allele of VRN-A3 might be associated with the regional adaptation of wheat. In this study, we elucidated its geographic distribution to assess the importance of the early flowering allele of VRN-A3 in worldwide wheat collection. From sequence analysis, we identified six VRN-A3 alleles with the 7- and 25-bp insertions, namely, Vrn-A3a-h2, Vrn-A3a-h3, Vrn-A3a-h4, Vrn-A3a-h5, Vrn-A3a-h6, and Vrn-A3c-h2 from wild emmer wheat, while we identified two VRN-A3 alleles with these insertions, Vrn-A3a-h2 and Vrn-A3c-h1 from cultivated tetraploid and hexaploid wheat species in addition to Vrn-A3a-h1. Among VRN-A3 alleles distributed in cultivated wheat, we found that Vrn-A3a-h2 promoted early heading, whereas Vrn-A3c-h1 did not affect heading time. Our analysis showed that the distribution of early flowering alleles of VRN-A3 dominated in cultivated emmer wheat in Ethiopia and India, which actually showed an early flowering phenotype. This implied that the early flowering alleles of VRN-A3 contribute to adaptability to a low-latitude environment in cultivated emmer wheat. We could not find durum (T. turgidum L. ssp. durum) and bread wheat (T. aestivum L. ssp. aestivum) accessions with these early flowering alleles. Our findings indicated that Vrn-A3a-h1 and Vrn-A3a-h2 were useful for breeding of early flowering cultivars in durum and bread wheat varieties.

DOI： 10.1007/s00425-021-03646-9

De Novo Genome Assembly of the Japanese Wheat Cultivar Norin 61 Highlights Functional Variation in Flowering Time and Fusarium-Resistant Genes in East Asian Genotypes. 査読

Kentaro K Shimizu, Dario Copetti, Moeko Okada, Thomas Wicker, Toshiaki Tameshige, Masaomi Hatakeyama, Rie Shimizu-Inatsugi, Catharine Aquino, Kazusa Nishimura, Fuminori Kobayashi, Kazuki Murata, Tony Kuo, Emily Delorean, Jesse Poland, Georg Haberer, Manuel Spannagl, Klaus F X Mayer, Juan Gutierrez-Gonzalez, Gary J Muehlbauer, Cecile Monat, Axel Himmelbach, Sudharsan Padmarasu, Martin Mascher, Sean Walkowiak, Tetsuya Nakazaki, Tomohiro Ban, Kanako Kawaura, Hiroyuki Tsuji, Curtis Pozniak, Nils Stein, Jun Sese, Shuhei Nasuda, Hirokazu Handa

Plant & cell physiology 62 ( 1 ) 8 - 27 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

Bread wheat is a major crop that has long been the focus of basic and breeding research. Assembly of its genome has been difficult because of its large size and allohexaploid nature (AABBDD genome). Following the first reported assembly of the genome of the experimental strain Chinese Spring (CS), the 10+ Wheat Genomes Project was launched to produce multiple assemblies of worldwide modern cultivars. The only Asian cultivar in the project is Norin 61, a representative Japanese cultivar adapted to grow across a broad latitudinal range, mostly characterized by a wet climate and a short growing season. Here, we characterize the key aspects of its chromosome-scale genome assembly spanning 15 Gb with a raw scaffold N50 of 22 Mb. Analysis of the repetitive elements identified chromosomal regions unique to Norin 61 that encompass a tandem array of the pathogenesis-related 13 family. We report novel copy-number variations in the B homeolog of the florigen gene FT1/VRN3, pseudogenization of its D homeolog and the association of its A homeologous alleles with the spring/winter growth habit. Furthermore, the Norin 61 genome carries typical East Asian functional variants different from CS, ranging from a single nucleotide to multi-Mb scale. Examples of such variation are the Fhb1 locus, which confers Fusarium head-blight resistance, Ppd-D1a, which confers early flowering, Glu-D1f for Asian noodle quality and Rht-D1b, which introduced semi-dwarfism during the green revolution. The adoption of Norin 61 as a reference assembly for functional and evolutionary studies will enable comprehensive characterization of the underexploited Asian bread wheat diversity.

DOI： 10.1093/pcp/pcaa152

Characterization of Parthenocarpic Fruit of 'Miyazaki-wase No. 1', a Tropical Squash (Cucurbita moschata L.) Cultivar 査読

Rihito Takisawa, Megumi Ogawa, Eri Maai, Kazusa Nishimura, Ryohei Nakano, Tetsuya Nakazaki

HORTICULTURE JOURNAL 90 ( 1 ) 68 - 74 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC HORTICULTURAL SCI

Parthenocarpy is a trait in which fruit set and development are induced without fertilization, thereby contributing to labor saving in fruit production. In Cucurbita species, parthenocarpic cultivars have been reported in Cucurbita pepo, but not in Cucurbita maxima and Cucurbita moschata. In this regard, the identification of parthenocarpic cultivars and clarification of their characteristics will contribute greatly to the research and breeding of the parthenocarpic trait in Cucurbita species. In this study, we aimed to genetically screen diverse Cucurbita accessions for high parthenocarpic ability and to elucidate the characteristics of the parthenocarpic cultivars discovered by the screening. We screened 33 accessions from squash genetic resources and found that a Cucurbita moschata cultivar, `Miyazaki-wale No. 1', exhibited parthenocarpy. In order to clarify the characteristics, we examined the fruit set rate, fruit expansion, and fruit quality of `Miyazaki-wase No. 1'. In the spring and fall experiments, the fruit set rate of parthenocarpic fruit was lower than that of pollinated fruit. On the other hand, there was no significant difference in the transverse diameter and weight of parthenocarpic and pollinated fruits at harvest. These results indicated that the fruit set ability of parthenocarpic fruit is inferior to that of pollinated fruit, although the fruit expansion ability of parthenocarpic fruit was almost the same as that of pollinated fruit. In addition, we compared the composition of parthenocarpic fruit with that of pollinated fruit at harvest and after storage in the fall experiment. The results demonstrated that there was no significant difference in all the examined compositions between the parthenocarpic and pollinated fruits at harvest. On the other hand, the beta-carotene concentration of parthenocarpic fruit was significantly lower than that of pollinated fruit one month and two months after harvest. These results indicated that parthenocarpic fruit development did not affect fruit quality at harvest, but had an effect on beta-carotene metabolism during storage. We showed that 'Miyazaki-wase No.1' is a parthenocarpic cultivar and clarified its characteristics. Based on the results, progress in research and breeding of parthenocarpic cultivars in Cucurbita species is anticipated in the future.

DOI： 10.2503/hortj.UTD-219

Identification of Genetic Factors Affecting Fruit Weight in the Tomato (Solanum lycopersicum L.) Cultivar 'Micro-Tom' 査読

Rihito Takisawa, Atsushi Nishida, Eri Maai, Kazusa Nishimura, Ryohei Nakano, Tetsuya Nakazaki

HORTICULTURE JOURNAL 90 ( 2 ) 209 - 214 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC HORTICULTURAL SCI

'Micro-Tom', a dwarf tomato cultivar, has been used as a convenient model system in tomato research. Previous studies have shown that several genes are involved in the phenotype, but to date no studs has focused on the fruit weight. In this study, we tried to clarify genetic factors that regulate the fruit weight of 'Micro-Tom' using an F-2 population derived from 'Micro-Tom' and `MPK-1', a mid-size tomato cultivar. The F-2 population showed a continuous and transgressive segregation in terms of fruit weight, suggesting that the fruit weight was regulated by multiple loci. To identify these loci, quantitative trait loci (QTL) analysis was performed. Three QTLs located on chromosomes 4, 7, and 9 were found to regulate fruit weight, and were designated as qfw4.1, qfw7.1, and qfw9.1. Of these QTLs, qfw4.1 exhibited the highest logarithm of the odds score. We confirmed the effect of qfw4.1 in the F3 population and showed that it regulates fruit weight without affecting locule number. In addition, being homozygous for the Micro-Tom allele at the marker linked to qfw4.1 reduced vegetative size, suggesting that qfw4.1 regulates not only fruit weight, but also vegetative size in 'Micro-Tom'.

DOI： 10.2503/hortj.UTD-252

Diurnal changes in chloroplast positioning and photosynthetic traits of C-4 grass finger millet 査読

Eri Maai, Kazusa Nishimura, Rihito Takisawa, Tetsuya Nakazaki

PLANT PRODUCTION SCIENCE 23 ( 4 ) 477 - 489 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

Mesophyll (M) chloroplasts in finger millet are known to aggregate to the bundle sheath side when leaves are constantly irradiated with extremely high-intensity light. This aggregative movement of M chloroplasts is also observed in natural environment, but whether a natural light regime is effective in inducing the response remains unclear. Abscisic acid is reported to trigger not only the aggregative movement but also stomatal closure, but photosynthetic responses accompanying the aggregative movement also remain unknown.We investigated changes in chloroplast positioning and photosynthetic traits under diurnal patterns of light, mimicking the natural light environment. M chloroplasts showed the aggregative movement with increasing light intensity whether it frequently fluctuated or not, and kept their aggregative positions in the midday. With decreasing light intensity, M chloroplasts returned to the random position in the evening. These results suggest that M chloroplasts often rearrange their intracellular positions during the daytime and that the chloroplast aggregative movement can be induced by a natural regime of light. The chloroplast aggregative movement was observed with increasing stomatal conductance, suggesting that stomatal closure is not crucial to trigger the chloroplast response.

DOI： 10.1080/1343943X.2020.1758171

Light stress-induced chloroplast movement and midday depression of photosynthesis in sorghum leaves 査読

Eri Maai, Kazusa Nishimura, Rihito Takisawa, Tetsuya Nakazaki

PLANT PRODUCTION SCIENCE 23 ( 2 ) 172 - 181 2020年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

Plants are exposed to high light intensity, high leaf temperatures and high air-to-leaf water vapor pressure deficit (ALVPD) during the day. These environmental stresses cause stomatal closure and photoinhibitory damage, leading to midday depression of photosynthesis. Chloroplast positioning is essential for the efficient operation of photosynthesis. However, chloroplast behavior before, during, and even after the midday depression of photosynthesis remains unknown. We investigated changes in the intracellular positioning of chloroplasts and photosynthetic traits under a diurnal pattern of light. Sorghum leaves were exposed to a 12-h regime of light mimicking the natural light environment, with constant leaf temperature and ALVPD. Net photosynthetic rate (P-n) showed a diurnal pattern, and midday depression in P-n was observed at 3.8 h of irradiation. Depression in P-n was attributed to stomatal limitation because the decrease in P-n was in accordance with the decrease in stomatal conductance. The maximum efficiency of photosystem II decreased with the increase in light intensity and remained low after 12 h of irradiation. Bundle sheath chloroplasts swelled after 8 h of irradiation, representing the accumulation of starch. Conversely, mesophyll chloroplasts exhibited avoidance response after 4 h of irradiation, and the avoidance position was maintained during the remainder of the daytime. These data suggest that chloroplasts are subject to light stress during and after the midday depression of photosynthesis. The intensity of natural light is excessive for most of the day and this light stress induces chloroplast avoidance response and depression of photosynthesis.

DOI： 10.1080/1343943X.2019.1673666