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Prof. Shuji Yokoi
Laboratory of Plant Breeding, Graduate School of Life and Environmental Sciences, Osaka Prefecture University

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0 Genetics
0 Plant Breeding
0 Plant Physiology
0 phase transition
0 Plant molecular biology

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Journal article
Published: 20 November 2020 in Horticulturae
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The genus Capsicum is comprised of 5 domesticated and more than 30 wild species. The region of nuclear ribosomal DNA internal transcribed spacers (rDNA-ITS) has widely been used for species identification, but has rarely been used in Capsicum. In this study, the evaluation of genetic diversity and a phylogenetic analysis were conducted using rDNA-ITS of 28 Capsicum accessions, including five domesticated and two wild species. We surveyed six conventional keys of domesticated species and another five traits in Capsicum accessions. Specific morphological characteristics were found in C. annuum, C. baccatum, and C.pubescens. Three subclones of each accession were sequenced, and rDNA-ITS polymorphisms were detected in all accessions excluding C. annuum, suggesting that incomplete concerted evolution occurred in rDNA-ITS of Capsicum. The genetic diversity was evaluated using nucleotide polymorphism and diversity. C. annuum had the lowest genetic diversity of all species in this study. The phylogenetic tree formed a species-specific clade for C. annuum, C. baccatum, and C. pubescens. The C. chinense clade existed in the C. frutescens clade, implying that it was a cultivated variant of C. frutescens. C. chacoense likely belonged to the C. baccatum complex according to its morphologic and genetic features. This study indicated that the rDNA-ITS region can be used for simple identification of domesticated Capsicum species.

ACS Style

Kumpei Shiragaki; Shuji Yokoi; Takahiro Tezuka. Phylogenetic Analysis and Molecular Diversity of Capsicum Based on rDNA-ITS Region. Horticulturae 2020, 6, 87 .

AMA Style

Kumpei Shiragaki, Shuji Yokoi, Takahiro Tezuka. Phylogenetic Analysis and Molecular Diversity of Capsicum Based on rDNA-ITS Region. Horticulturae. 2020; 6 (4):87.

Chicago/Turabian Style

Kumpei Shiragaki; Shuji Yokoi; Takahiro Tezuka. 2020. "Phylogenetic Analysis and Molecular Diversity of Capsicum Based on rDNA-ITS Region." Horticulturae 6, no. 4: 87.

Original research
Published: 17 August 2020 in Plant Direct
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Seed abortion and ovary abscission, two types of postzygotic reproductive barriers, are often observed in interspecific and/or interploidy crosses in plants. However, the mechanisms underlying these reproductive barriers remain unclear. Here, we show that the distinct types of seed developmental abnormalities (type I and type II seed abortion) occur in a phased manner as maternal to paternal genome dosage increases and that type II seed abortion is followed by ovary abscission. We revealed that these two types of seed developmental abnormalities are observed during seed development in the interploidy‐interspecific crosses of Nicotiana suaveolens and N. tabacum. Moreover, in the cross showing type II seed abortion, several events, such as changes in abscission‐related gene expression and lignin deposition, occurred in the ovary abscission zone, eventually leading to ovary abscission. Notably, successive increases in maternal ploidy using ploidy manipulated lines resulted in successive type I and type II seed abortions, and the latter was accompanied by ovary abscission. Conversely, both types of seed abortion and ovary abscission could be overcome with a ploidy manipulation technique that balances parental ploidy levels. We thus concluded that a high maternal genome excess cross may cause severe seed developmental defects and ovary abscission. Based on our findings, we propose a model explaining the abortion phenomena, where an interaction between the promotive and inhibitive effects of the parental genomes determines the developmental destiny of seeds. Significance statement We demonstrate that a stepwise increase in maternal ploidy results in a stepwise increase in seed abortion severity, leading to ovary abscission in plants. We propose a model explaining the abortion phenomena, where an interaction between the promotive and inhibitive effects of the parental genomes determines the developmental destiny of seeds.

ACS Style

Hai He; Shuji Yokoi; Takahiro Tezuka. A high maternal genome excess causes severe seed abortion leading to ovary abscission in Nicotiana interploidy‐interspecific crosses. Plant Direct 2020, 4, e00257 .

AMA Style

Hai He, Shuji Yokoi, Takahiro Tezuka. A high maternal genome excess causes severe seed abortion leading to ovary abscission in Nicotiana interploidy‐interspecific crosses. Plant Direct. 2020; 4 (8):e00257.

Chicago/Turabian Style

Hai He; Shuji Yokoi; Takahiro Tezuka. 2020. "A high maternal genome excess causes severe seed abortion leading to ovary abscission in Nicotiana interploidy‐interspecific crosses." Plant Direct 4, no. 8: e00257.

Journal article
Published: 01 January 2020 in Breeding Science
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Hybrid weakness in Capsicum is characterized by the termination of leaf differentiation after the development of several leaves. F1 plants in some crosses between Capsicum annuum and Capsicum chinense show weakness; this phenomenon has not been investigated in detail since first reported. In the present study, we characterized morphologically and physiologically hybrid weakness in Capsicum. F1 plants did not show weaker growth than their parents 20 days after germination (DAG), but at 40 DAG, the hybrid weakness phenotype was evidenced by almost complete arrest of new leaf formation, delayed increase in plant height, and reduced upper internode length. The shoot apical meristem (SAM) of F1 plants exhibited delayed development and an abnormal structure characterized by a flat shape and the presence of fuzzy cell layers on the surface. These abnormal SAMs of F1 plants may lead to dwarfism. Dead cells and accumulation of H2O2 were visually detected in leaves of F1 plants, and cell death was considered to be programmed, as it was accompanied by internucleosomal fragmentation of DNA. The expression of immunity marker genes PR1 and PR2 was upregulated in leaves of F1 plants. These results suggest that a hypersensitive response-like reaction is involved in Capsicum hybrid weakness.

ACS Style

Kumpei Shiragaki; Shuji Yokoi; Takahiro Tezuka. A hypersensitive response-like reaction is involved in hybrid weakness in F1 plants of the cross Capsicum annuum × Capsicum chinense. Breeding Science 2020, 70, 19137 -437.

AMA Style

Kumpei Shiragaki, Shuji Yokoi, Takahiro Tezuka. A hypersensitive response-like reaction is involved in hybrid weakness in F1 plants of the cross Capsicum annuum × Capsicum chinense. Breeding Science. 2020; 70 (4):19137-437.

Chicago/Turabian Style

Kumpei Shiragaki; Shuji Yokoi; Takahiro Tezuka. 2020. "A hypersensitive response-like reaction is involved in hybrid weakness in F1 plants of the cross Capsicum annuum × Capsicum chinense." Breeding Science 70, no. 4: 19137-437.

Original article
Published: 29 July 2019 in Planta
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Morphological and genetic markers indicate that in sorghum, the juvenile-to-adult phase transition occurs during the fourth and fifth leaf stages. This timing differs from those reported for other plants. The juvenile-to-adult (JA) phase transition is an important event for optimizing vegetative growth and reproductive success in plants. Among the Poaceae crops, which are a vital food source for humans, studies of the JA phase transition have been restricted to rice and maize. We studied the morphological and genetic changes that occur during the early development of sorghum and found that dramatic changes occur in shoot architecture during the early vegetative stages. Changes were observed in leaf size, leaf shape, numbers of trichomes, and size of the shoot apical meristem. In particular, the length/width ratios of the leaf blades in the fifth and upper leaves were completely different from those of the second to fourth leaves. The fifth and upper leaves have trichomes on their adaxial sides, which were absent on the lower leaves. We also analyzed expression of two microRNAs that are known to be molecular markers of the JA phase transition and found that expression of miR156 was highest in the second to fourth leaves and then was gradually down-regulated, whereas miR172 expression followed the opposite pattern. These results suggest that in sorghum, the second and third leaves represent the juvenile phase, the fourth and fifth leaves are in the transition stage, and the sixth and upper leaves are in the adult phase. Thus, the JA phase transition occurs during the fourth and fifth leaf stages. These findings are expected to be useful for understanding the early development of sorghum.

ACS Style

Shumpei Hashimoto; Takahiro Tezuka; Shuji Yokoi. Morphological changes during juvenile-to-adult phase transition in sorghum. Planta 2019, 250, 1557 -1566.

AMA Style

Shumpei Hashimoto, Takahiro Tezuka, Shuji Yokoi. Morphological changes during juvenile-to-adult phase transition in sorghum. Planta. 2019; 250 (5):1557-1566.

Chicago/Turabian Style

Shumpei Hashimoto; Takahiro Tezuka; Shuji Yokoi. 2019. "Morphological changes during juvenile-to-adult phase transition in sorghum." Planta 250, no. 5: 1557-1566.

Regular paper
Published: 21 May 2019 in Journal of Plant Research
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Reproductive isolation, including prezygotic and postzygotic barriers, is a mechanism that separates species. Many species in the Nicotiana section Suaveolentes exhibit reproductive isolation in crosses with Nicotiana tabacum. In this study, we investigated whether the chromosome numbers and ploidy levels of eight Nicotiana suaveolens accessions are related to the reproductive isolation after crosses with N. tabacum by flow cytometry and chromosome analyses. Additionally, the internal transcribed spacer (ITS) regions of the eight N. suaveolens accessions were sequenced and compared with the previously reported sequences of 22 Suaveolentes species to elucidate the phylogenetic relationships in the section Suaveolentes. We revealed that four N. suaveolens accessions comprised 64 chromosomes, while the other four accessions carried 32 chromosomes. Depending on the ploidy levels of N. suaveolens, several types of reproductive isolation were observed after crosses with N. tabacum, including decreases in the number of capsules and the germination rates of hybrid seeds, as well as hybrid lethality and abscission of enlarged ovaries at 12-17 days after pollination. A phylogenetic analysis involving ITS sequences divided the eight N. suaveolens accessions into three distinct clades. Based on the results, we confirmed that N. suaveolens accessions vary regarding ploidy levels and reproductive isolation mechanisms in crosses with N. tabacum. These accessions will be very useful for revealing and characterizing the reproductive isolation mechanisms in interspecific crosses and their relationships with ploidy levels.

ACS Style

Hai He; Takahiro Iizuka; Maho Maekawa; Kumi Sadahisa; Toshinobu Morikawa; Masanori Yanase; Shuji Yokoi; Masayuki Oda; Takahiro Tezuka. Nicotiana suaveolens accessions with different ploidy levels exhibit different reproductive isolation mechanisms in interspecific crosses with Nicotiana tabacum. Journal of Plant Research 2019, 132, 461 -471.

AMA Style

Hai He, Takahiro Iizuka, Maho Maekawa, Kumi Sadahisa, Toshinobu Morikawa, Masanori Yanase, Shuji Yokoi, Masayuki Oda, Takahiro Tezuka. Nicotiana suaveolens accessions with different ploidy levels exhibit different reproductive isolation mechanisms in interspecific crosses with Nicotiana tabacum. Journal of Plant Research. 2019; 132 (4):461-471.

Chicago/Turabian Style

Hai He; Takahiro Iizuka; Maho Maekawa; Kumi Sadahisa; Toshinobu Morikawa; Masanori Yanase; Shuji Yokoi; Masayuki Oda; Takahiro Tezuka. 2019. "Nicotiana suaveolens accessions with different ploidy levels exhibit different reproductive isolation mechanisms in interspecific crosses with Nicotiana tabacum." Journal of Plant Research 132, no. 4: 461-471.

Journal article
Published: 17 July 2018 in Environmental and Experimental Botany
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Flowering date reflects the adjustment of a plant’s growth period to a given environment. This is true of rice, which is a major food source around the world. We tested whether rice plants can recognize and record natural variation in their growth environments and thus control flowering in their progeny. We grew seedlings of two japonica cultivars from the same seed stock at two locations, in cool and warm climates, in Japan until they produced seeds. We then tested their progeny at the same locations. The progeny of mother plants of both cultivars grown in a cool climate flowered significantly earlier (by 1 to 6 days) than the progeny of mother plants grown in a warm climate. This transgenerational effect was partially explained by water temperatures during the vegetative growth stage. This is the first study to show the effect of transgenerational effect of natural environments on flowering date in rice.

ACS Style

Takemasa Koumoto; Naohiro Aoki; Takahiro Hamasaki; Shigehide Shiga; Shuji Yokoi; Hiroyuki Shimono. Transgenerational effect of maternal growth environment on flowering date in rice (Oryza sativa L.). Environmental and Experimental Botany 2018, 155, 307 -312.

AMA Style

Takemasa Koumoto, Naohiro Aoki, Takahiro Hamasaki, Shigehide Shiga, Shuji Yokoi, Hiroyuki Shimono. Transgenerational effect of maternal growth environment on flowering date in rice (Oryza sativa L.). Environmental and Experimental Botany. 2018; 155 ():307-312.

Chicago/Turabian Style

Takemasa Koumoto; Naohiro Aoki; Takahiro Hamasaki; Shigehide Shiga; Shuji Yokoi; Hiroyuki Shimono. 2018. "Transgenerational effect of maternal growth environment on flowering date in rice (Oryza sativa L.)." Environmental and Experimental Botany 155, no. : 307-312.

Correction
Published: 15 January 2018 in Euphytica
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This article was published with an erroneous version of one of the affiliations. Please find the correct affiliations herewith.

ACS Style

Naoko Kitamoto; Kazuhiro Nishikawa; Yoshinori Tanimura; Shoji Urushibara; Takuya Matsuura; Shuji Yokoi; Yoshihito Takahata; Susumu Yui. Correction to: Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating. Euphytica 2018, 214, 30 .

AMA Style

Naoko Kitamoto, Kazuhiro Nishikawa, Yoshinori Tanimura, Shoji Urushibara, Takuya Matsuura, Shuji Yokoi, Yoshihito Takahata, Susumu Yui. Correction to: Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating. Euphytica. 2018; 214 (2):30.

Chicago/Turabian Style

Naoko Kitamoto; Kazuhiro Nishikawa; Yoshinori Tanimura; Shoji Urushibara; Takuya Matsuura; Shuji Yokoi; Yoshihito Takahata; Susumu Yui. 2018. "Correction to: Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating." Euphytica 214, no. 2: 30.

Article
Published: 04 December 2017 in Euphytica
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We developed new F1 hybrids of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that allow cultivation earlier in spring without heating by introducing extremely late-bolting alleles at two homologs of the flowering repressor Flowering Locus C (BrFLC2 and BrFLC3) from non-heading ‘Leafy Green Parental Line No. 2’. These new F1 hybrids were produced by the following four steps. First, the extremely late bolting selected lines were developed. These selected lines headed in spring after overwintering cultivation, whereas the conventional F1 cultivars flowered. Secondly, an investigation of the three plantings showed that our F1 hybrids formed heads when seeds were sown from mid-February to early March, whereas the conventional F1 cultivar did not form heads because of premature bolting. Thirdly, we identified some F1 hybrids with extremely late bolting during early spring cultivation in an investigation of many F1 hybrids. Finally, based on an investigation across four cold regions for 2 years, we compared the commercialization rate, defined as the proportion of plants greater than 2000 g in weight and with a flowering stalk less than 10 cm long. Then we identified a F1 of MS02 × 12-04 which had a high commercialization rate on average (92%), whereas the rates of three conventional F1 cultivars were only 0–2%. In the near future, these F1 hybrids will be valuable late-bolting cultivars despite climate change, permitting stable cultivation and harvest over wide regions.

ACS Style

Naoko Kitamoto; Kazuhiro Nishikawa; Yoshinori Tanimura; Shoji Urushibara; Takuya Matsuura; Shuji Yokoi; Yoshihito Takahata; Susumu Yui. Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating. Euphytica 2017, 213, 292 .

AMA Style

Naoko Kitamoto, Kazuhiro Nishikawa, Yoshinori Tanimura, Shoji Urushibara, Takuya Matsuura, Shuji Yokoi, Yoshihito Takahata, Susumu Yui. Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating. Euphytica. 2017; 213 (12):292.

Chicago/Turabian Style

Naoko Kitamoto; Kazuhiro Nishikawa; Yoshinori Tanimura; Shoji Urushibara; Takuya Matsuura; Shuji Yokoi; Yoshihito Takahata; Susumu Yui. 2017. "Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating." Euphytica 213, no. 12: 292.

Journal article
Published: 10 April 2017 in Plant Breeding
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Plants develop juvenile phase to adult phase in vegetative stage. Although soybean is a very important crop worldwide, there has been only one study of the juvenile–adult phase change. In this study, we determined that the juvenile–adult phase change occurred at different stages in two soybean cultivars that differ in their photosensitivity. Cultivar ‘Enrei’ (E1e2e3E4) is weakly photosensitive and cultivar ‘Peking’ (E1E2E3E4) is strongly photosensitive. In ‘Enrei’, the leaf size gradually increased at a constant leaf position regardless of the difference in day length. In ‘Peking’ plants transferred to short-day conditions at several leaf development stages, leaf size gradually increased at different leaf positions. Expression of miR156 by ‘Enrei’ transferred to short-day conditions had nearly the same pattern as that of ‘Enrei’ grown under long-day conditions. In ‘Peking’, the expression of miR156 had different patterns in younger leaves of plants subjected to either a short-day treatment or long-day conditions. These results indicate that the E2 and E3 loci that regulate photosensitivity also regulate the expression of miR156 and the juvenile–adult phase change in soybean.

ACS Style

Suguru Ozawa; Katsunori Hatakeyama; Yoshihito Takahata; Shuji Yokoi. The transition time from the juvenile phase to the adult phase differs in soybean cultivars ‘Enrei’ and ‘Peking’. Plant Breeding 2017, 129, 265 -392.

AMA Style

Suguru Ozawa, Katsunori Hatakeyama, Yoshihito Takahata, Shuji Yokoi. The transition time from the juvenile phase to the adult phase differs in soybean cultivars ‘Enrei’ and ‘Peking’. Plant Breeding. 2017; 129 (3):265-392.

Chicago/Turabian Style

Suguru Ozawa; Katsunori Hatakeyama; Yoshihito Takahata; Shuji Yokoi. 2017. "The transition time from the juvenile phase to the adult phase differs in soybean cultivars ‘Enrei’ and ‘Peking’." Plant Breeding 129, no. 3: 265-392.

Journal article
Published: 01 January 2017 in Breeding Science
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Heading date is an important event to ensure successful seed production. Although foxtail millet (Setaria italica (L.) P.Beauv.) is an important foodstuff in semiarid regions around the world, the genetic basis determining heading date is unclear. To identify genomic regions regulating days to heading (DTH), we conducted a QTL-seq analysis based on combining whole-genome re-sequencing and bulked-segregant analysis of an F2 population derived from crosses between the middle-heading cultivar Shinanotsubuhime and the early-heading cultivar Yuikogane. Under field conditions, transgressive segregation of DTH toward late heading was observed in the F2 population. We made three types of bulk samples: Y-bulk (early-heading), S-bulk (late-heading) and L-bulk (extremely late-heading). By genome-wide comparison of SNPs in the Y-bulk vs. the S-bulk and the Y-bulk vs. the L-bulk, we identified two QTLs associated with DTH. The first QTL, qDTH2, was detected on chromosome 2 from the Y-bulk and S-bulk comparison. The second QTL, qDTH7, was detected on chromosome 7 from the Y-bulk and L-bulk comparison. The Shinanotsubuhime allele for qDTH2 caused late heading in the F2 population, whereas the Yuikogane allele for qDTH7 led to extremely late heading. These results suggest that allelic differences in both qDTH2 and qDTH7 determine regional adaptability in S. italica.

ACS Style

Yuki Yoshitsu; Masato Takakusagi; Akira Abe; Hiroki Takagi; Aiko Uemura; Hiroki Yaegashi; Ryohei Terauchi; Yoshihito Takahata; Katsunori Hatakeyama; Shuji Yokoi. QTL-seq analysis identifies two genomic regions determining the heading date of foxtail millet, Setaria italica (L.) P.Beauv. Breeding Science 2017, 67, 518 -527.

AMA Style

Yuki Yoshitsu, Masato Takakusagi, Akira Abe, Hiroki Takagi, Aiko Uemura, Hiroki Yaegashi, Ryohei Terauchi, Yoshihito Takahata, Katsunori Hatakeyama, Shuji Yokoi. QTL-seq analysis identifies two genomic regions determining the heading date of foxtail millet, Setaria italica (L.) P.Beauv. Breeding Science. 2017; 67 (5):518-527.

Chicago/Turabian Style

Yuki Yoshitsu; Masato Takakusagi; Akira Abe; Hiroki Takagi; Aiko Uemura; Hiroki Yaegashi; Ryohei Terauchi; Yoshihito Takahata; Katsunori Hatakeyama; Shuji Yokoi. 2017. "QTL-seq analysis identifies two genomic regions determining the heading date of foxtail millet, Setaria italica (L.) P.Beauv." Breeding Science 67, no. 5: 518-527.

Original article
Published: 20 July 2016 in Plant Cell Reports
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We identified three physical positions associated with embryo yield in microspore culture of Brassica rapa by segregation distortion analysis. We also confirmed their genetic effects on the embryo yield. Isolated microspore culture is well utilized for the production of haploid or doubled-haploid plants in Brassica crops. Brassica rapa cv. ‘Ho Mei’ is one of the most excellent cultivars in embryo yield of microspore culture. To identify the loci associated with microspore embryogenesis, segregation analysis of 154 DNA markers anchored to B. rapa chromosomes (A01–A10) was performed using a population of microspore-derived embryos obtained from an F1 hybrid between ‘CR-Seiga’, a low yield cultivar in microspore-derived embryos, and ‘Ho Mei’. Three regions showing significant segregation distortion with increasing ‘Ho Mei’ alleles were detected on A05, A08 and A09, although these regions showed the expected Mendelian segregation ratio in an F2 population. The additive effect of alleles in these regions on embryo yield was confirmed in a BC3F1 population. One region on A08 containing Br071-5c had a higher effect than the other regions. Polymorphism of nucleotide sequences around the Br071-5c locus was investigated to find the gene possibly responsible for efficient embryogenesis from microspores.

ACS Style

Hiroyasu Kitashiba; Kumiko Taguchi; Ikuyo Kaneko; Kiyofumi Inaba; Shuji Yokoi; Yoshihito Takahata; Takeshi Nishio. Identification of loci associated with embryo yield in microspore culture of Brassica rapa by segregation distortion analysis. Plant Cell Reports 2016, 35, 2197 -2204.

AMA Style

Hiroyasu Kitashiba, Kumiko Taguchi, Ikuyo Kaneko, Kiyofumi Inaba, Shuji Yokoi, Yoshihito Takahata, Takeshi Nishio. Identification of loci associated with embryo yield in microspore culture of Brassica rapa by segregation distortion analysis. Plant Cell Reports. 2016; 35 (10):2197-2204.

Chicago/Turabian Style

Hiroyasu Kitashiba; Kumiko Taguchi; Ikuyo Kaneko; Kiyofumi Inaba; Shuji Yokoi; Yoshihito Takahata; Takeshi Nishio. 2016. "Identification of loci associated with embryo yield in microspore culture of Brassica rapa by segregation distortion analysis." Plant Cell Reports 35, no. 10: 2197-2204.

Journal article
Published: 13 June 2016 in Plant Production Science
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ACS Style

Takemasa Koumoto; Naoko Saito; Naohiro Aoki; Toshiki Iwasaki; Shigenao Kawai; Shuji Yokoi; Hiroyuki Shimono. Effects of salt and low light intensity during the vegetative stage on susceptibility of rice to male sterility induced by chilling stress during the reproductive stage. Plant Production Science 2016, 19, 497 -507.

AMA Style

Takemasa Koumoto, Naoko Saito, Naohiro Aoki, Toshiki Iwasaki, Shigenao Kawai, Shuji Yokoi, Hiroyuki Shimono. Effects of salt and low light intensity during the vegetative stage on susceptibility of rice to male sterility induced by chilling stress during the reproductive stage. Plant Production Science. 2016; 19 (4):497-507.

Chicago/Turabian Style

Takemasa Koumoto; Naoko Saito; Naohiro Aoki; Toshiki Iwasaki; Shigenao Kawai; Shuji Yokoi; Hiroyuki Shimono. 2016. "Effects of salt and low light intensity during the vegetative stage on susceptibility of rice to male sterility induced by chilling stress during the reproductive stage." Plant Production Science 19, no. 4: 497-507.

Journal article
Published: 01 January 2016 in Plant Biotechnology
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Salinity stress is a major abiotic stress for plants worldwide. This study was carried out to determine the variation in salt tolerance for 12 different genotypes belonging to three different tomato species: Solanum lycopersicum (L), S. peruvianum (L) and S. pimpinellifolium (L). Shoot apices and callus cultures were exposed to different levels of salinity stress ranging from no salt (control) to 100, 200 and 300 mmol L-1 NaCl. All growth and physiological parameters were significantly affected by salt stress. Most shoot apices of S. lycopersicum did not develop roots when exposed to low NaCl levels, whereas apices of S. peruvianum and S. pimpinellifolium developed roots when exposed to all salt levels. This difference in salt tolerance was clearly shown on the basis of root fresh weights and root surface areas. Callus growth in response to increased salinity was much greater in S. peruvianum and S. pimpinellifolium than in S. lycopersicum. The Cl- and Na+ concentrations increased significantly with increasing salt in the three species, although the S. peruvianum lines accumulated more ions compared with the others. As the salt concentration increased, less K+ accumulated in S. lycopersicum compared to the related wild species. The results obtained in this study suggest that S. peruvianum line 0043-1 was the accession with the best salt tolerance. The most tolerant cultivated tomato (S. lycopersicum) cultivar was 'Rutgers.' Both S. peruvianum line 0043-1 and S. lycopersicum 'Rutgers' are good candidates for inclusion in tomato breeding programs for salt-tolerance.

ACS Style

Haitham Zaki; Shuji Yokoi. A comparative in vitro study of salt tolerance in cultivated tomato and related wild species. Plant Biotechnology 2016, 33, 361 -372.

AMA Style

Haitham Zaki, Shuji Yokoi. A comparative in vitro study of salt tolerance in cultivated tomato and related wild species. Plant Biotechnology. 2016; 33 (5):361-372.

Chicago/Turabian Style

Haitham Zaki; Shuji Yokoi. 2016. "A comparative in vitro study of salt tolerance in cultivated tomato and related wild species." Plant Biotechnology 33, no. 5: 361-372.

Original article
Published: 26 November 2015 in Physiologia Plantarum
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Male sterility induced by low temperatures (LTs) during the reproductive stage is a major constraint for temperate zone rice. To detect physiological quantitative trait loci (QTLs), we modeled genotypic variation in the physiological processes involved in low temperature spikelet sterility on the basis of anther length (AL), a proxy for microspore and pollen grain number per anther. The model accounted for 83% of the genotypic variation in potential AL at normal temperature and the ability to maintain AL at LT. We tested the model on 208 recombinant inbred lines of cold‐tolerant ‘Tohoku‐PL3’ (PL3) × cold‐sensitive ‘Akihikari’ (AH) for 2 years. QTLs for spikelet fertility (FRT) at LT were detected on chromosomes 5 (QTL for Cold Tolerance at Reproductive stage, qCTR5) and 12 (qCTR12). qCTR12 was annotated with the ability to maintain AL under LTs. qCTR5 was in a region shared with QTLs for culm length and heading date. Genome‐wide expression analysis showed 798 genes differentially expressed in the spikelets between the parents at LTs. Of these, 12 were near qCTR5 and 23 were near qCTR12. Gene expression analysis confirmed two candidate genes for qCTR5 (O‐methyltransferase ZRP4, Os05g0515600; beta‐1,3‐glucanase‐like protein, Os05g0535100) and one for qCTR12 (conserved hypothetical protein, Os12g0550600). Nucleotide polymorphisms (21 deletions, 2 insertions and 10 single nucleotide polymorphisms) in PL3 were found near the candidate conserved hypothetical protein (Os12g0550600) and upstream in PL3, but not in AH. Haplotype analysis revealed that this gene came from ‘Kuchum’. The combination of mapping physiological QTLs with gene expression analysis can be extended to identify other genes for abiotic stress response in cereals.

ACS Style

Hiroyuki Shimono; Akira Abe; Naohiro Aoki; Takemasa Koumoto; Masahiro Sato; Shuji Yokoi; Eiki Kuroda; Takashi Endo; Ken-Ich Saeki; Kuniaki Nagano. Combining mapping of physiological quantitative trait loci and transcriptome for cold tolerance for counteracting male sterility induced by low temperatures during reproductive stage in rice. Physiologia Plantarum 2015, 157, 175 -192.

AMA Style

Hiroyuki Shimono, Akira Abe, Naohiro Aoki, Takemasa Koumoto, Masahiro Sato, Shuji Yokoi, Eiki Kuroda, Takashi Endo, Ken-Ich Saeki, Kuniaki Nagano. Combining mapping of physiological quantitative trait loci and transcriptome for cold tolerance for counteracting male sterility induced by low temperatures during reproductive stage in rice. Physiologia Plantarum. 2015; 157 (2):175-192.

Chicago/Turabian Style

Hiroyuki Shimono; Akira Abe; Naohiro Aoki; Takemasa Koumoto; Masahiro Sato; Shuji Yokoi; Eiki Kuroda; Takashi Endo; Ken-Ich Saeki; Kuniaki Nagano. 2015. "Combining mapping of physiological quantitative trait loci and transcriptome for cold tolerance for counteracting male sterility induced by low temperatures during reproductive stage in rice." Physiologia Plantarum 157, no. 2: 175-192.

Journal article
Published: 15 November 2013 in Euphytica
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We investigated the molecular basis of an extremely late bolting, non-heading ‘Leafy Green Parental Line No. 2 (Tsukena No. 2)’, to obtain suitable DNA markers for breeding the late bolting trait in Chinese cabbage (Brassica rapa L. ssp. pekinensis). We found that Tsukena No. 2 contains a ~5 kbp large insertion near the 5′ end of the first intron of BrFLC2, BrFLC3 and BrFLC3′, which are homologs of an Arabidopsis repressor gene for floral transition, FLOWERING LOCUS C (FLC). The transcript abundance of BrFLC1 in Tsukena No. 2 was repressed during cold exposure to the same level as found in a mid-season bolting commercial F1 variety “Muso” (heading Chinese cabbage) and an early-bolting parent of commercial F1 varieties, “Early” (Sakata Co.), whereas repression of BrFLC2 and BrFLC3 containing the large insertion was weak. Furthermore, QTL analysis of a F2 population derived from the Tsukena No. 2 × “Early” revealed that polymorphisms at the BrFLC2 and BrFLC3 loci explained 46.0 and 9.9 % of the phenotypic variation in the bolting time of vernalized plants, respectively. In Arabidopsis, cold-induced repression of FLC and maintenance of that repression are associated with the first intron of FLC. Our study suggests that a naturally occurring large insertion in the first intron resulted in weak repression of BrFLC2 and BrFLC3 during cold exposure and therefore explains the extremely late bolting of the Tsukena No. 2 cultivar.

ACS Style

Naoko Kitamoto; Susumu Yui; Kazuhiro Nishikawa; Yoshihito Takahata; Shuji Yokoi. A naturally occurring long insertion in the first intron in the Brassica rapa FLC2 gene causes delayed bolting. Euphytica 2013, 196, 213 -223.

AMA Style

Naoko Kitamoto, Susumu Yui, Kazuhiro Nishikawa, Yoshihito Takahata, Shuji Yokoi. A naturally occurring long insertion in the first intron in the Brassica rapa FLC2 gene causes delayed bolting. Euphytica. 2013; 196 (2):213-223.

Chicago/Turabian Style

Naoko Kitamoto; Susumu Yui; Kazuhiro Nishikawa; Yoshihito Takahata; Shuji Yokoi. 2013. "A naturally occurring long insertion in the first intron in the Brassica rapa FLC2 gene causes delayed bolting." Euphytica 196, no. 2: 213-223.

Short communication
Published: 18 May 2013 in Planta
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Juvenile-to-adult phase change is an indispensable event which guarantees a successful life cycle. Phase change has been studied in maize, Arabidopsis and rice, but is mostly unknown in other species. Soybean/Fabaceae plants undergo drastic changes of shoot architecture at the early vegetative stage including phyllotactic change and leaf type alteration from simple to compound. These characteristics make soybean/Fabaceae plants an interesting taxon for investigating vegetative phase change. Following the expansion of two cotyledons, two simple leaves simultaneously emerge in opposite phyllotaxy. The phyllotaxy of the third and fourth leaves is not fixed; both opposite and distichous phyllotaxis are observed within the same population. Leaves were compound from the third leaf. But the third leaf was rarely simple. Morphological and quantitative changes in early vegetative phase were recognized in leaf size, leaf shape, number of trichomes, stipule size and shape, and shoot meristem shape. Two microRNA genes, miR156 and miR172, are known to be associated with vegetative phase change. Examination of the expression level revealed that miR156 expression was high in the first two leaves and subsequently down-regulated, and that of miR172 showed the inverse expression pattern. These expression patterns coincided with the case of other species. Taken all data together, the first and second leaves represent juvenile phase, the fifth and upper leaves adult phase, and the third and fourth leaves intermediate stage. Further investigation of soybean phase change would give fruitful understandings on plant development.

ACS Style

Takanori Yoshikawa; Suguru Ozawa; Naoki Sentoku; Jun-Ichi Itoh; Yasuo Nagato; Shuji Yokoi. Change of shoot architecture during juvenile-to-adult phase transition in soybean. Planta 2013, 238, 229 -237.

AMA Style

Takanori Yoshikawa, Suguru Ozawa, Naoki Sentoku, Jun-Ichi Itoh, Yasuo Nagato, Shuji Yokoi. Change of shoot architecture during juvenile-to-adult phase transition in soybean. Planta. 2013; 238 (1):229-237.

Chicago/Turabian Style

Takanori Yoshikawa; Suguru Ozawa; Naoki Sentoku; Jun-Ichi Itoh; Yasuo Nagato; Shuji Yokoi. 2013. "Change of shoot architecture during juvenile-to-adult phase transition in soybean." Planta 238, no. 1: 229-237.

Journal article
Published: 01 January 2013 in Breeding Science
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Factors affecting reliable plant regeneration from unfertilized ovule culture of gentians (Gentiana spp.) were examined. Cold pretreatment (4°C) of flower buds enhanced or maintained production of embryo-like structure (ELS). When 43 genotypes were surveyed in two different labs, 40 of them produced ELSs ranging from 0.01 to 26.5 ELSs per flower bud. No ELSs could be obtained in three genotypes. A significant correlation (r = 0.64) was observed between the number of ELS per flower and the frequency of responding flower buds. Eight genotypes of G. triflora, which were used as common materials in two different labs, produced ELSs in both labs. The ploidy levels of a total of 1,515 regenerated plantlets were determined, revealing that the majority of these plants consisted of haploids (57.9%) and diploids (34.3%). However, the frequency of haploids and diploids was different between G. triflora and G. scabra, and G. triflora showed higher frequencies of haploids than G. scabra. When haploids were treated with oryzalin for chromosome doubling, diploids and tetraploids were obtained. These results demonstrate that the unfertilized ovule culture technique of gentians is a powerful tool for obtaining haploids and DHs because of its reproducible and reliable nature and application to a wide range of genotypes.

ACS Style

Hisako Doi; Nobue Hoshi; Eri Yamada; Shuji Yokoi; Masahiro Nishihara; Takashi Hikage; Yoshihito Takahata. Efficient haploid and doubled haploid production from unfertilized ovule culture of gentians (Gentiana spp.). Breeding Science 2013, 63, 400 -406.

AMA Style

Hisako Doi, Nobue Hoshi, Eri Yamada, Shuji Yokoi, Masahiro Nishihara, Takashi Hikage, Yoshihito Takahata. Efficient haploid and doubled haploid production from unfertilized ovule culture of gentians (Gentiana spp.). Breeding Science. 2013; 63 (4):400-406.

Chicago/Turabian Style

Hisako Doi; Nobue Hoshi; Eri Yamada; Shuji Yokoi; Masahiro Nishihara; Takashi Hikage; Yoshihito Takahata. 2013. "Efficient haploid and doubled haploid production from unfertilized ovule culture of gentians (Gentiana spp.)." Breeding Science 63, no. 4: 400-406.

Original article
Published: 31 March 2012 in Plant Biotechnology Reports
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A number of factors influencing microspore embryogenesis and plant regeneration were examined in five subspecies (rapa, oleifera, niposinica, perviridis, broccoletto) of B. rapa. Addition of 6-benzylaminopurine (BA) in 1/2 NLN-10 medium improved the embryo yield by 2–12 fold. Addition of activated charcoal (AC) in the medium was not effective for microspore embryogenesis. Moreover, AC canceled the positive effect of BA, when the medium containing both BA and AC was used. Of 24 genotypes examined for microspore embryogenesis, 22 genotypes of all five subspecies produced embryos ranging from 0.02 to 15.0 per 2 × 105 microspores, but two genotypes were not responsive. Low temperature pretreatment of flower buds significantly improved the microspore embryogenesis. When cotyledonary embryos were subcultured on a filter paper placed on top of 0.8 % agar-solidified B5-2 medium and 1.6 % agar B5-2 medium, plant regenerations were increased 4–8 fold compared to 0.8 % agar medium. The ploidy levels of regenerated plants in three genotypes were determined by flow cytometry, revealing that 66–100 % of them were diploid. The results enable the advancement of breeding programs and genetic studies in B. rapa.

ACS Style

Yu Takahashi; Shuji Yokoi; Yoshihito Takahata. Effects of genotypes and culture conditions on microspore embryogenesis and plant regeneration in several subspecies of Brassica rapa L. Plant Biotechnology Reports 2012, 6, 297 -304.

AMA Style

Yu Takahashi, Shuji Yokoi, Yoshihito Takahata. Effects of genotypes and culture conditions on microspore embryogenesis and plant regeneration in several subspecies of Brassica rapa L. Plant Biotechnology Reports. 2012; 6 (4):297-304.

Chicago/Turabian Style

Yu Takahashi; Shuji Yokoi; Yoshihito Takahata. 2012. "Effects of genotypes and culture conditions on microspore embryogenesis and plant regeneration in several subspecies of Brassica rapa L." Plant Biotechnology Reports 6, no. 4: 297-304.

Original articles
Published: 01 January 2012 in The Journal of Horticultural Science and Biotechnology
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Radish (Raphanus sativus) is an important crucifer vegetative crop in Japan. We studied the morphological and anatomical characteristics of radish roots over a 6-week period using three radish cultivars with three different root shapes: long-type (Lt), round-type (Rt), and thin-type (Tt). We found that significant differences in the thickness of the roots first appeared 4 weeks after sowing. In Lt and Rt plants, the roots thickened rapidly, especially in the middle section that is composed of the lower part of the hypocotyl and the upper part of the taproot. The taproot increased in length in Lt plants, but failed to elongate in Rt plants. In Tt plants, the roots showed much smaller increases in mean diameter and length. Transverse sections through the taproots showed significant differences, both in cell number and in cell size 4 weeks after sowing. Lt and Rt plants contained more cells in the secondary xylem and phloem than Tt plants, and cell expansion was also greater in the storage roots of the Lt and Rt cultivars. These results will contribute to a better understanding of the development of radish roots of different shape.

ACS Style

Haitham Zaki; Y. Takahata; S. Yokoi. Analysis of the morphological and anatomical characteristics of roots in three radish (Raphanus sativus) cultivars that differ in root shape. The Journal of Horticultural Science and Biotechnology 2012, 87, 172 -178.

AMA Style

Haitham Zaki, Y. Takahata, S. Yokoi. Analysis of the morphological and anatomical characteristics of roots in three radish (Raphanus sativus) cultivars that differ in root shape. The Journal of Horticultural Science and Biotechnology. 2012; 87 (2):172-178.

Chicago/Turabian Style

Haitham Zaki; Y. Takahata; S. Yokoi. 2012. "Analysis of the morphological and anatomical characteristics of roots in three radish (Raphanus sativus) cultivars that differ in root shape." The Journal of Horticultural Science and Biotechnology 87, no. 2: 172-178.

Journal article
Published: 22 April 2011 in Molecular Genetics and Genomics
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Many plants require circadian clock and light information for the photoperiodic control of flowering. In Arabidopsis, a long-day plant (LDP), flowering is triggered by the circadian clock-controlled expression of CONSTANS (CO) and light stabilization of the CO protein to induce FT (FLOWERING LOCUS T). In rice, a short-day plant (SDP), the CO ortholog Heading date 1 (Hd1) regulates FT ortholog Hd3a, but regulation of Hd3a by Hd1 differs from that in Arabidopsis. Here, we report that phytochrome B (phyB)-mediated suppression of Hd3a is a primary cause of long-day suppression of flowering in rice, based on the three complementary discoveries. First, overexpression of Hd1 causes a delay in flowering under SD conditions and this effect requires phyB, suggesting that light modulates Hd1 control of Hd3a transcription. Second, a single extension of day length decreases Hd3a expression proportionately with the length of daylight. Third, Hd1 protein levels in Hd1-overexpressing plants are not altered in the presence of light. These results also suggest that phyB-mediated suppression of Hd3a expression is a component of the molecular mechanism for critical day length in rice.

ACS Style

Ryo Ishikawa; Mayumi Aoki; Ken-Ichi Kurotani; Shuji Yokoi; Tomoko Shinomura; Makoto Takano; Ko Shimamoto. Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice. Molecular Genetics and Genomics 2011, 285, 461 -470.

AMA Style

Ryo Ishikawa, Mayumi Aoki, Ken-Ichi Kurotani, Shuji Yokoi, Tomoko Shinomura, Makoto Takano, Ko Shimamoto. Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice. Molecular Genetics and Genomics. 2011; 285 (6):461-470.

Chicago/Turabian Style

Ryo Ishikawa; Mayumi Aoki; Ken-Ichi Kurotani; Shuji Yokoi; Tomoko Shinomura; Makoto Takano; Ko Shimamoto. 2011. "Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice." Molecular Genetics and Genomics 285, no. 6: 461-470.