Faculty Profiles - ARAKI Ryoichi

Published Papers - ARAKI Ryoichi

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Drought stress alters iron accumulation in Sorghum bicolor seeds

Ryoichi Araki, Yuka Takano, Hidetoshi Miyazaki, Hiroyuki Ii, Ping An

ENVIRONMENTAL AND EXPERIMENTAL BOTANY ( PERGAMON-ELSEVIER SCIENCE LTD ) 204 2022.12

Sorghum (Sorghum bicolor L.) is a cultivated food crop with iron-rich seeds that thrives in semi-arid areas. Although the mechanism of iron transport has been investigated in detail at the molecular level, the effects of drought stress on its regulation remain unclear. We cultivated sorghum in a chamber without (control) and with drought stress to determine iron accumulation in seeds. The drought stress treatment significantly increased the iron content by approximately 2-fold in seeds and decreased it by 0.6-fold in leaves. The results of RNA -sequencing leaves indicated that drought stress impaired the expression of genes involved in photosynthesis. This agreed with the finding that drought stress significantly reduced plant biomass. The expression of genes encoding vacuole iron transporter and ferritin were increased under drought stress. These expression profiles were confirmed by quantitative polymerase chain reaction, which indicated that expression of genes encoding the vacuole iron transporter and ferritin was significantly increased in leaves and seeds under drought stress. Furthermore, photosynthesis impaired by drought stress might trigger a disturbance in iron homeostasis. Therefore, increased vacuolar transporters and ferritin transcription might be important for safely storing excess iron. Our data suggested that maintaining iron homeostasis via vacuole iron transporters and ferritin enhances iron accumulation in seeds under drought stress.

Fatty acid compositions of triacylglycerols in flax (Linum usitatissimum L.) seeds with varied seeding dates and nitrogen fertilization in a temperate region of Japan Seeding date and fatty acids in flux seed

Tomoko Hatanaka, Naoki Yamamoto, Ryoichi Araki, Mitsuyoshi Kishigami, Tomomi Nakamoto, Takehiro Masumura, Toshio Sugimoto

SOIL SCIENCE AND PLANT NUTRITION ( TAYLOR & FRANCIS LTD ) 2021.04 [Refereed]

We monitored fatty acid compositions of the triacylglycerol (TAG) fractions in flax (Linum usitatissimum L.) seeds cultivated in pots with different seeding dates and nitrogen (N) fertilizing conditions in a temperate region Wakayama, Japan. Five flax cultivars were seeded in early and late December 2017, and in late January 2018, and matured in April, May, June and July in the order of planting. Three types of N fertilizer were applied for plants seeded in January Fatty acid profiles in seed TAG fractions were varied among the cultivation conditions. A cluster analysis dissected the fatty acid profiles of the same genotype with different seeding dates. Principal component analyses revealed inverse correlations between saturated and unsaturated fatty acid contents, which could be affected by temperature, N fertilization, and genotypic factors. The highest correlation was observed between alpha-linolenic and oleic acid contents, which showed a strong inverse relationship across genotypes (r= 0.964, n = 15). The ratio of alpha-linolenic acid content to that of oleic acid in seeds from plants seeded in early December were higher than those seeded on the other two dates across genotypes. We suppose that seeding date and N supply might be crucial determinants of flax lipid quality in temperate regions.

田植え後の水田におけるアマ茎の浸漬が水稲生育に及ぼす影響とアマの体験型観光農業の素材としての利用について

杉本敏男, 山本直樹, 岸上光克, 小林匡輔, 荒木良一

日本土壌肥料学雑誌 91 ( 5 ) 402 - 406 2020.10 [Refereed]

多様なイネの品種を用いたペットボトル栽培

古谷太一・荒木良一（Part： Corresponding author )

和歌山大学教育学部紀要第70集 51 - 55 2020.02

Effect of Traditional Cultivation Management on CO2 Flux in the Dry Tropical Cropland of South India

Mayuko Seki, Soh Sugihara, Hidetoshi Miyazaki, Ryoichi Araki, Muniandi Jegadeesan, Shun Ishiyama, Ueru Tanaka, Haruo Tanaka

AGRONOMY-BASEL ( MDPI ) 9 ( 7 ) 347 2019.07 [Refereed]

Soils in tropical croplands are becoming degraded because of soil carbon (C) depletion. Local farmers in South India use a specific management of traditional cultivation, i.e., broadcast seeding. However, for sustainable C management, there is no quantitative data on the CO2 flux under this management. Our objectives were to (1) estimate the annual CO2 flux, and (2) evaluate the effect of traditional cultivation management (seeding rate) on the CO2 flux. Our field experiment was conducted in South India, from 2015 to 2017, including two cultivation periods with four cultivation management treatments (traditional cultivation management plot (T), fixed density plot (FD), no thinning plot (NT), and bare plot (B)). The seeding rate in the FD plot was ca. 50% of the T plot. We applied 1.1 Mg C ha(-1) farmyard manure just before the experiment as a C input. We found that broadcasting, thinning, and cultivation increased soil moisture, while the CO2 efflux rate showed no significant difference between treatments throughout the experimental period. This indicates that cultivation management did not affect the CO2 flux. The total CO2 fluxes for two years were estimated at 2.2-2.7 Mg C ha(-1). Our results indicate that it is necessary to apply larger or more frequent C inputs to prevent C depletion.

南インド、タミル・ナードゥ州におけるソルガム栽培に織り込まれた家畜飼料獲得法の評価

宮嵜英寿・関真由子・杉原創・荒木良一・M. Jegadeesan・田中樹

雑穀研究 34 1-6. 2019.07 [Refereed]

半乾燥地におけるソルガム（K8品種）の散播ー間引き栽培の有効性

荒木良一・宮武千波・関真由子・杉原創・MUNIANDI Jegadeesan・宮嵜英寿・田中樹（Part： Lead author,　Corresponding author )

雑穀研究 34 7-13. 2019.07 [Refereed]

SPL7 locally regulates copper-homeostasis-related genes in Arabidopsis

Ryoichi Araki （Part： Lead author )

Journal of Plant Physiology 224-225 137 - 143 2018.05 [Refereed]

Feasibility of Cross-Curricular Energy Education Around Technology Education

井嶋博, 嶋本光芳, 荒木良一

和歌山大学教育学部紀要. 教育科学 = Bulletin of the Faculty of Education, Wakayama University. 和歌山大学教育学部紀要委員会編 ( 和歌山大学教育学部 ) 68 ( 2 ) 61 - 63 2018.02

エネルギーは我々の生活において欠かせないもののひとつであり、現代社会においては、その資源や用途は多様で、利用方法は高度化されてきている。このようなことから新学習指導要領ではエネルギー教育を環境教育の一つに位置付け、様々な学年で複数の教科の中で取り扱われるようになっている。本稿では各教科、学年におけるエネルギー教育の目的と意義を確認し、中学校技術科における教育分野の一つである「エネルギーの変換と利用」を中心とした教科を横断するエネルギー教育の可能性や問題点について述べる。

Essence and Problem of Education in Secondary Technology Education : Based on the Material and Processing

嶋本光芳, 荒木良一, 井嶋博

和歌山大学教育学部紀要. 教育科学 = Bulletin of the Faculty of Education, Wakayama University. 和歌山大学教育学部紀要委員会編 ( 和歌山大学教育学部 ) 68 ( 2 ) 57 - 60 2018.02

Report of Maize Cultivation in Laboratory Farm Fields for Living Environmental Studies

荒木良一, 小林匡輔, 梶村麻紀子, 井嶋博（Part： Lead author,　Corresponding author )

和歌山大学教育学部紀要. 自然科学 = Bulletin of the Faculty of Education, Wakayama University. 和歌山大学教育学部紀要委員会編 ( 和歌山大学教育学部 ) 68 ( 1 ) 251 - 254 2018.01

Essence and Problem of Technical Art in Secondary School Education : Based on the Culture of Living Organisms

荒木良一, 嶋本光芳, 井嶋博（Part： Lead author,　Corresponding author )

和歌山大学教育学部紀要. 自然科学 = Bulletin of the Faculty of Education, Wakayama University. 和歌山大学教育学部紀要委員会編 ( 和歌山大学教育学部 ) 68 ( 1 ) 247 - 250 2018.01

技術分野の生物育成分野では生育技術と育成技術に関する内容を扱っている。本稿では生物育成分野の中の植物の栽培における現状について学習指導要領や教科書の内容を整理し、生物育成分野の特徴や課題について考察する。さらに、技術分野が基礎から応用まで扱っているために学生の技術への関心を誘発する可能性が高いので、広範な知識を必要とする技術分野教員をサポートする仕組みが必要であることを指摘した。加えて附属農場で行われた実習についても考察した。

双眼実体顕微鏡を用いたクマムシ観察の授業実践

梶村麻紀子, 寺本由, 廣瀬正紀, 岩田勝哉, 古賀庸憲, 荒木良一, 高須英樹

和歌山大学教職大学院紀要 2 179 - 184 2018

Emerging possibilities of the use of mugineic acids opened up by large-scale chemical synthesis

Murata, J, Araki, R, Murata, Y, Namba, K

Bioscience and Industry ( バイオインダストリー協会 ) 73 ( 6 ) 462 - 466 2015.11 [Refereed] [Invited]

Phytosiderophores revisited: 2 '-deoxymugineic acid-mediated iron uptake triggers nitrogen assimilation in rice (Oryza sativa L.) seedlings

Ryoichi Araki, Kosuke Namba, Yoshiko Murata, Jun Murata

PLANT SIGNALING & BEHAVIOR ( TAYLOR & FRANCIS INC ) 10 ( 6 ) e1031940 2015.06 [Refereed] [Invited]

Poaceae plants release phytosiderophores into the rhizosphere in order to chelate iron (Fe), which often exists in insoluble forms especially under high pH conditions. The impact of phytosiderophore treatment at the physiological and molecular levels in vivo remains largely elusive, although the biosynthesis of phytosiderophores and the transport of phytosiderophore-metal complexes have been well studied. We recently showed that the application of 30M of the chemically synthesized phytosiderophore 2-deoxymugineic acid (DMA) was sufficient for apparent full recovery of otherwise considerably reduced growth of hydroponic rice seedlings at high pH. Moreover, unexpected induction of high-affinity nitrate transporter gene expression as well as nitrate reductase activity indicates that the nitrate response is linked to Fe homeostasis. These data shed light on the biological relevance of DMA not simply as a Fe chelator, but also as a trigger that promotes plant growth by reinforcing nitrate assimilation.

2'-Deoxymugineic acid promotes growth of rice (Oryza sativa L.) by orchestrating iron and nitrate uptake processes under high pH conditions

Ryoichi Araki, Kayoko Kousaka, Kosuke Namba, Yoshiko Murata, Jun Murata （Part： Lead author )

Plant Journal ( Blackwell Publishing Ltd ) 81 ( 2 ) 233 - 246 2015.01 [Refereed]

Poaceae plants release 2'-deoxymugineic acid (DMA) and related phytosiderophores to chelate iron (Fe), which often exists as insoluble Fe(III) in the rhizosphere, especially under high pH conditions. Although the molecular mechanisms behind the biosynthesis and secretion of DMA have been studied extensively, little information is known about whether DMA has biological roles other than chelating Fe in vivo. Here, we demonstrate that hydroponic cultures of rice (Oryza sativa) seedlings show almost complete restoration in shoot height and soil-plant analysis development (SPAD) values after treatment with 3-30 μm DMA at high pH (pH 8.0), compared with untreated control seedlings at normal pH (pH 5.8). These changes were accompanied by selective accumulation of Fe over other metals. While this enhanced growth was evident under high pH conditions, DMA application also enhanced seedling growth under normal pH conditions in which Fe was fairly accessible. Microarray and qRT-PCR analyses revealed that exogenous DMA application attenuated the increased expression levels of various genes related to Fe transport and accumulation. Surprisingly, despite the preferential utilization of ammonium over nitrate as a nitrogen source by rice, DMA application also increased nitrate reductase activity and the expression of genes encoding high-affinity nitrate transporters and nitrate reductases, all of which were otherwise considerably lower under high pH conditions. These data suggest that exogenous DMA not only plays an important role in facilitating the uptake of environmental Fe, but also orchestrates Fe and nitrate assimilation for optimal growth under high pH conditions.

2'-Deoxymugineic acid promotes growth of rice (Oryza sativa L.) by orchestrating iron and nitrate uptake processes under high pH conditions

Ryoichi Araki, Kayoko Kousaka, Kosuke Namba, Yoshiko Murata, Jun Murata （Part： Lead author )

Plant Journal ( Blackwell Publishing Ltd ) 81 ( 2 ) 233 - 246 2015.01 [Refereed]

Poaceae plants release 2'-deoxymugineic acid (DMA) and related phytosiderophores to chelate iron (Fe), which often exists as insoluble Fe(III) in the rhizosphere, especially under high pH conditions. Although the molecular mechanisms behind the biosynthesis and secretion of DMA have been studied extensively, little information is known about whether DMA has biological roles other than chelating Fe in vivo. Here, we demonstrate that hydroponic cultures of rice (Oryza sativa) seedlings show almost complete restoration in shoot height and soil-plant analysis development (SPAD) values after treatment with 3-30 μm DMA at high pH (pH 8.0), compared with untreated control seedlings at normal pH (pH 5.8). These changes were accompanied by selective accumulation of Fe over other metals. While this enhanced growth was evident under high pH conditions, DMA application also enhanced seedling growth under normal pH conditions in which Fe was fairly accessible. Microarray and qRT-PCR analyses revealed that exogenous DMA application attenuated the increased expression levels of various genes related to Fe transport and accumulation. Surprisingly, despite the preferential utilization of ammonium over nitrate as a nitrogen source by rice, DMA application also increased nitrate reductase activity and the expression of genes encoding high-affinity nitrate transporters and nitrate reductases, all of which were otherwise considerably lower under high pH conditions. These data suggest that exogenous DMA not only plays an important role in facilitating the uptake of environmental Fe, but also orchestrates Fe and nitrate assimilation for optimal growth under high pH conditions.

Analysis of photosynthetic electron transport in Arabidopsis thaliana under iron deficiency.

Araki R, Shikanai T （Part： Lead author,　Corresponding author )

J. Crop Res. ( The Society of Crop Science and Breeding in Kinki, Japan ) 59 ( 11 ) 15 - 15 2014 [Refereed]

Iron is an essential nutrient for plants, and intensive studies have focused on plant responses to iron deficiency. In the field, iron availability often limits the productivity of crops, particularly in alkaline calcareous soil with insoluble iron. Iron is essential for chloroplasts, as a cofactor of many proteins involved in electron transport and reactive oxygen species (ROS) scavenging. Because chloroplasts are the major site of ROS generation, it is important for plants to maintain proper chloroplast function under iron deficiency to avoid photodamage. To study the primary damage to the photosynthetic apparatus by iron deficiency in Arabidopsis thaliana, we took advantage of chlorophyll fluorescence analysis, a nondestructive method of monitoring photosynthetic electron transport in leaves. Chlorosis was observed, and photosystem II (PSII) was severely photodamaged in seedlings grown under severe iron-deficient conditions. In contrast, mild iron deficiency decreased the non-photochemical quenching of chlorophyll fluorescence, which represents the dissipation of absorbed light energy from PSII prior to PSII photodamage. Although transferring seedlings from iron-supplemented to iron-deficient conditions is often used to study plant responses to iron deficiency, photosynthetic electron transport was disturbed before visible symptoms of iron deficiency were observed.

Novel bioresources for studies of Brassica oleracea: identification of a kale MYB transcription factor responsible for glucosinolate production

Ryoichi Araki, Akiko Hasumi, Osamu Ishizaki Nishizawa, Katsunori Sasaki, Ayuko Kuwahara, Yuji Sawada, Yasushi Totoki, Atsushi Toyoda, Yoshiyuki Sakaki, Yimeng Li, Kazuki Saito, Toshiya Ogawa, Masami Yokota Hirai （Part： Lead author )

PLANT BIOTECHNOLOGY JOURNAL ( WILEY-BLACKWELL ) 11 ( 8 ) 1017 - 1027 2013.10 [Refereed]

Plants belonging to the Brassicaceae family exhibit species-specific profiles of glucosinolates (GSLs), a class of defence compounds against pathogens and insects. GSLs also exhibit various human health-promoting properties. Among them, glucoraphanin (aliphatic 4-methylsulphinylbutyl GSL) has attracted the most attention because it hydrolyses to form a potent anticancer compound. Increased interest in developing commercial varieties of Brassicaceae crops with desirable GSL profiles has led to attempts to identify genes that are potentially valuable for controlling GSL biosynthesis. However, little attention has been focused on genes of kale (Brassica oleracea var. acephala). In this study, we established full-length kale cDNA libraries containing 59904 clones, which were used to generate an expressed sequence tag (EST) data set with 119204 entries. The EST data set clarified genes related to the GSL biosynthesis pathway in kale. We specifically focused on BoMYB29, a homolog of Arabidopsis MYB29/PMG2/HAG3, not only to characterize its function but also to demonstrate its usability as a biological resource. BoMYB29 overexpression in wild-type Arabidopsis enhanced the expression of aliphatic GSL biosynthetic genes and the accumulation of aliphatic GSLs. When expressed in the myb28myb29 mutant, which exhibited no detectable aliphatic GSLs, BoMYB29 restored the expression of biosynthetic genes and aliphatic GSL accumulation. Interestingly, the ratio of methylsulphinyl GSL content, including glucoraphanin, to that of methylthio GSLs was greatly increased, indicating the suitability of BoMYB29 as a regulator for increasing methylsulphinyl GSL content. Our results indicate that these biological resources can facilitate further identification of genes useful for modifications of GSL profiles and accumulation in kale.

Time-course changes in fungal elicitor-induced lignan synthesis and expression of the relevant genes in cell cultures of Linum album

Sedigheh Esmaeilzadeh Bahabadi, Mozafar Sharifi, Mehrdad Behmanesh, Naser Safaie, Jun Murata, Ryoichi Araki, Tohru Yamagaki, Honoo Satake

JOURNAL OF PLANT PHYSIOLOGY ( ELSEVIER GMBH, URBAN & FISCHER VERLAG ) 169 ( 5 ) 487 - 491 2012.03 [Refereed]

Linum album has been shown to accumulate anti-tumor podophyllotoxin (PTOX) and its related lignans. In the present study, we examined the effects of five fungal extracts on the production of lignans in L album cell cultures. Fusarium graminearum extract induced the highest increase of PTOX [140 mu g g(-1) dry weight (DW) of the L. album cell culture] which is seven-fold greater than the untreated control, while Rhizopus stolonifer extract enhanced the accumulation of lariciresinol, instead of PTOX, up to 365 mu mg g(-1) DW, which was 8.8-fold greater than the control. Quantitative PCR analyses showed that expression of the enzyme genes responsible for the PTOX biosynthesis cascade, such as pinoresinol-lariciresinol reductase (PLR), phenylalanine ammonia-lyase (PAL), cinnamoyl-CoA reductase (CCR) and cinnamyl-alcohol dehydrogenase (CAD) genes, were also up-regulated in a fungal extract-selective fashion. These results provide evidence that the fungal extracts used in this study differentially increase the production of PTOX or larisiresinol via the up-regulation of the genes in lignan biosynthesis in L album cell cultures, and suggest that such selective actions of fungal elicitors on the lignan synthesis will lead to more efficient metabolic engineering-based production of FTOX and other beneficial lignans using L album cell cultures. (C) 2011 Elsevier GmbH. All rights reserved.

A Novel Barley Yellow Stripe 1-Like Transporter (HvYSL2) Localized to the Root Endodermis Transports Metal-Phytosiderophore Complexes

Ryoichi Araki, Jun Murata, Yoshiko Murata （Part： Lead author )

PLANT AND CELL PHYSIOLOGY ( OXFORD UNIV PRESS ) 52 ( 11 ) 1931 - 1940 2011.11 [Refereed]

Recent advances in our understanding of how graminaceous plants take up insoluble forms of iron from the rhizosphere and mobilize them in plant tissues are primarily based on the identification of various transporters that are specific to metal-phytosiderophore (PS) complexes containing mugineic acid and deoxymugineic acid. Barley (Hordeum vulgare L.) yellow stripe 1 (HvYS1) is a metal-PS transporter that preferentially transports Fe(III)-PS compared with other metal complexes. Here, we report the cloning and characterization of HvYSL2, a novel metal-PS transporter encoding gene. HvYSL2 is composed of 702 amino acids with 14 transmembrane domains, which are conserved among this class of transporters, and exhibits 67.3% identity to HvYS1. Electrophysiological experiments with Xenopus laevis oocytes revealed that HvYSL2 transports PS complexes with Fe(III), Zn(II), Ni(II), Cu(II), Mn(II) or Co(II); this constitutes a broader range of substrate preference than HvYS1. Real-time PCR analysis revealed that HvYSL2 mRNA is expressed in shoots and also in roots, where it is induced under iron-deficient conditions. Moreover, immunohistochemistry in roots revealed that HvYSL2 is localized to the endodermis, whereas HvYS1 is expressed primarily in the epidermis. These data suggest that HvYSL2 is spatially distinct from HvYS1 and plays a unique role in delivering a broad range of essential metals in barley.

High-affinity nitrate uptake by rice (Oryza sativa) coleoptiles

Shu Takayanagi, Yuma Takagi, Ryoichi Araki, Hiroshi Hasegawa

JOURNAL OF PLANT RESEARCH ( SPRINGER TOKYO ) 124 ( 2 ) 305 - 309 2011.03 [Refereed]

Nitrate uptake by rice coleoptiles was evaluated using (15)N-nitrate in relation to the expression of high-affinity nitrate uptake-related genes, OsNRT2s (OsNRT2.1-2.4) and OsNAR2s (OsNAR2.1 and 2.2). Apparent nitrate uptake by coleoptiles was about one-sixth of that by hydroponically cultured seedling roots. Real-time RT-PCR analysis revealed that OsNRT2.1, a root-specific key gene of inducible high-affinity transport system for nitrate, was most strongly induced in coleoptiles following nitrate supply initiation, while other OsNRT2s and OsNAR2s showed modest induction. These results suggest that rice coleoptiles may have high-affinity transport systems for nitrate similar to roots, and can be model organs for nutrient uptake by submerged plant shoots.

Omics-based identification of Arabidopsis Myb transcription factors regulating aliphatic glucosinolate biosynthesis

Masami Yokota Hirai, Kenjiro Sugiyama, Yuji Sawada, Takayuki Tohge, Takeshi Obayashi, Akane Suzuki, Ryoichi Araki, Nozomu Sakurai, Hideyuki Suzuki, Koh Aoki, Hideki Goda, Osamu Ishizaki Nishizawa, Daisuke Shibata, Kazuki Saito

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA ( NATL ACAD SCIENCES ) 104 ( 15 ) 6478 - 6483 2007.04 [Refereed]

Understanding plant metabolism as an integrated system is essential for metabolic engineering aimed at the effective production of compounds useful to human life and the global environment. The "omics" approach integrates transcriptome and metabolome data into a single data set and can lead to the identification of unknown genes and their regulatory networks involved in metabolic pathways of interest. one of the intriguing, although poorly described metabolic pathways in plants is the biosynthesis of glucosinolates (GSLs), a group of bioactive secondary products derived from amino acids that are found in the family Brassicaceae. Here we report the discovery of two R2R3-Myb transcription factors that positively control the biosynthesis of GSLs in Arabidopsis thaliana by an integrated omics approach. Combined transcriptome coexpression analysis of publicly available, condition-independent data and the condition-specific (i.e., sulfur-deficiency) data identified Myb28 and Myb29 as candidate transcription factor genes specifically involved in the regulation of aliphatic GSL production. Analysis of a knockout mutant and ectopic expression of the gene demonstrated that Myb28 is a positive regulator for basal-level production of aliphatic GSLs. Myb29 presumably plays an accessory function for methyl jasmonate-mediated induction of a set of aliphatic GSL biosynthetic genes. Overexpression of Myb28 in Arabidopsis-cultured suspension cells, which do not normally synthesize GSLs, resulted in the production of large amounts of GSLs, suggesting the possibility of efficient industrial production of GSLs by manipulation of these transcription factors. A working model for regulation of GSL production involving these genes, renamed Production of Methionine-Derived Glucosinolate (PMG) 1 and 2, are postulated.

Expression of rice (Oryza sativa L.) genes involved in high-affinity nitrate transport during the period of nitrate induction

Ryoichi Araki, Hiroshi Hasegawa （Part： Lead author )

BREEDING SCIENCE ( JAPANESE SOC BREEDING ) 56 ( 3 ) 295 - 302 2006.09 [Refereed]

When breeding crops that utilize nitrogen efficiently, it is important to reveal the regulation of nitrate uptake at the molecular level. We focused on the expression of two nitrate uptake-related genes, NRT2 and NAR2, and nitrate uptake during the nitrate induction. Four rice NRT2s (OsNRT2.1 similar to 2.4) and two NAR2s (OsNAR2.1 similar to 2.2) were identified in the rice genome database. We analyzed the expression of the genes in the roots and shoots after supply of nitrate with or without ammonium pretreatment by the RT-PCR method. The apparent nitrate uptake was also measured. Differential expression of OsNRT2.1 and OsNRT2.2, which have the same ORF with different 5'- and 3'-UTR, was observed in the seedlings pretreated with ammonium. The apparent nitrate uptake synchronously increased after supply of nitrate with the expression pattern of OsNRT2.1 in roots either with or without ammonium pretreatment. The expression of OsNAR2.1, which is thought to be an activator gene for the function of NRT2, was also coordinated with that of OsNRT2.1. On the other hand, OsNRT2.2 was already expressed after ammonium pretreatment, suggesting that OsNRT2.2 would be transcribed to take up nitrate in flooded soils. The present results indicate that OsNRT2.1, OsNRT2.2 and OsNAR2.1 are candidate genes when breeding for efficient use of nitrate in rice.

ヨシ（Phragmites australis）の遺伝的改良－序論－

長谷川博, 荒木良一, 野見山誉, 宮角裕喜, 玉井紀子, 伴あずさ

近畿作物・育種研究 51: 13-17. 2006 [Refereed]

Genetic differences in nitrate uptake in two clones of the common reed, Phragmites australis

R Araki, M Mori, H Hasegawa （Part： Lead author )

BREEDING SCIENCE ( JAPANESE SOC BREEDING ) 55 ( 3 ) 297 - 302 2005.09 [Refereed]

Phragmites australis, common reed, could be useful in removing eutrophic substances from river and lake water. In this study, the genetic differences in nitrate uptake ability of the reed were investigated with a view to breeding a reed plant useful for phytoremediation. Two reed clones (W-6 and W-8) isolated from a reed community in the lakeside wetland along Lake Biwa, Japan, were used for a study on the physiological and molecular basis of nitrate uptake. K(m)s for nitrate uptake were 80.8 and 45.2 mu M and V(max)s for nitrate uptake were 10.62 and 2.37 mu mol g(-1) root f.w. h(-1) in W-6 and W-8, respectively, suggesting that there were critical differences in kinetic parameters for nitrate uptake. To investigate these differences at the molecular level, we isolated a high-affinity nitrate transporter gene (NRT2) from the two reed clones and analyzed the reed NRT2 structure and expression. The deduced amino acid sequence of the reed NRT2 consisted of 523 residues and had a high similarity to NRT2 from other monocots. Reed NRT2 was strongly expressed in roots treated with 200 mu M nitrate. There were three amino acid substitutions of the reed NRT2 between W-6 and W-8. Differences in NRT2 transcription were also observed between the two clones. It was not clear whether the difference in kinetic parameters for nitrate was due to the reed NRT2 structure or expression. These results indicate the possibility of selecting genotypes more useful for the removal of nitrate.

イネにおける硝酸吸収および硝酸還元酵素活性の遺伝解析.

東明沙, 荒木良一, 山内裕香, 長谷川博

近畿作物・育種研究 49: 17-20. 2004 [Refereed]

ヨシ(Phragmites australis)の高親和性硝酸トランスポーター遺伝子(NRT2)について.

荒木良一, 森真理, 森正之, 長谷川博（Part： Lead author )

近畿作物・育種研究 48: 57-59. 2003 [Refereed]

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