Language：English   Publishing type：Research paper (scientific journal)  

Phosphorus (P) is a key macronutrient whose availability has a profound effect on plant growth and productivity. The understanding of the mechanism underlying P availability-responsive P acquisition has expanded largely in the past decade; however, effects of other environmental factors on P acquisition and utilization remain elusive. Here, by imaging natural variation in phosphate uptake in 200 natural accessions of Arabidopsis, we identify two accessions with low phosphate uptake activity, Lm-2 and CSHL-5. In these accessions, natural variants of phytochrome B were found to cause both decreased light sensitivity and lower phosphate uptake. Furthermore, we also found that expression levels of phosphate starvation-responsive genes are directly modulated by phytochrome interacting factors (PIF) PIF4/PIF5 and HY5 transcription factors whose activity is under the control of phytochromes. These findings disclose a new molecular mechanism underlying red-light-induced activation of phosphate uptake, which is responsible for different activity for P acquisition in some natural accessions of Arabidopsis.

DOI： 10.1038/s41477-018-0294-7

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELIFE SCIENCES PUBLICATIONS LTD  

The root cap has a fundamental role in sensing environmental cues as well as regulating root growth via altered meristem activity. Despite this well-established role in the control of developmental processes in roots, the root cap's function in nutrition remains obscure. Here, we uncover its role in phosphate nutrition by targeted cellular inactivation or phosphate transport complementation in Arabidopsis, using a transactivation strategy with an innovative high-resolution real-time P-33 imaging technique. Remarkably, the diminutive size of the root cap cells at the root-to-soil exchange surface accounts for a significant amount of the total seedling phosphate uptake (approximately 20%). This level of Pi absorption is sufficient for shoot biomass production (up to a 180% gain in soil), as well as repression of Pi starvation-induced genes. These results extend our understanding of this important tissue from its previously described roles in environmental perception to novel functions in mineral nutrition and homeostasis control.

DOI： 10.7554/eLife.14577

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Phosphate (Pi) is a macronutrient that is essential for plant life. Several regulatory components involved in Pi homeostasis have been identified, revealing a very high complexity at the cellular and subcellular levels. Determining the Pi content in plants is crucial to understanding this regulation, and short real-time (33)Pi uptake imaging experiments have shown Pi movement to be highly dynamic. Furthermore, gene modulation by Pi is finely controlled by localization of this ion at the tissue as well as the cellular and subcellular levels. Deciphering these regulations requires access to and quantification of the Pi pool in the various plant compartments. This review presents the different techniques available to measure, visualize and trace Pi in plants, with a discussion of the future prospects.

DOI： 10.1093/pcp/pcv208

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DOI： 10.1111/nph.13591

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Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Soil phosphate represents the only source of phosphorus for plants and, consequently, is its entry into the trophic chain. This major component of nucleic acids, phospholipids, and energy currency of the cell (ATP) can limit plant growth because of its low mobility in soil. As a result, root responses to low phosphate favor the exploration of the shallower part of the soil, where phosphate tends to be more abundant, a strategy described as topsoil foraging. We will review the diverse developmental strategies that can be observed among plants by detailing the effect of phosphate deficiency on primary and lateral roots. We also discuss the formation of cluster roots: an advanced adaptive strategy to cope with low phosphate availability observed in a limited number of species. Finally, we will put this work into perspective for future research directions.

DOI： 10.1104/pp.114.244541

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Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Plant purple acid phosphatases (PAPs) belong to a relatively large gene family whose individual functions are poorly understood. Three PAP isozymes that are up-regulated in the cell walls of phosphate (Pi)-starved (-Pi) Arabidopsis thaliana suspension cells were purified and identified by MS as AtPAP12 (At2g27190), AtPAP25 (At4g36350) and AtPAP26 (At5g34850). AtPAP12 and AtPAP26 were previously isolated from the culture medium of -Pi cell cultures, and shown to be secreted by roots of Arabidopsis seedlings to facilitate Pi scavenging from soil-localized organophosphates. AtPAP25 exists as a 55kDa monomer containing complex NX(S/T) glycosylation motifs at Asn172, Asn367 and Asn424. Transcript profiling and immunoblotting with anti-AtPAP25 immune serum indicated that AtPAP25 is exclusively synthesized under -Pi conditions. Coupled with potent mixed-type inhibition of AtPAP25 by Pi (I-50=50m), this indicates a tight feedback control by Pi that prevents AtPAP25 from being synthesized or functioning as a phosphatase except when Pi levels are quite low. Promoter-GUS reporter assays revealed AtPAP25 expression in shoot vascular tissue of -Pi plants. Development of an atpap25 T-DNA insertion mutant was arrested during cultivation on soil lacking soluble Pi, but rescued upon Pi fertilization or complementation with AtPAP25. Transcript profiling by quantitative RT-PCR indicated that Pi starvation signaling was attenuated in the atpap25 mutant. AtPAP25 exhibited near-optimal phosphatase activity with several phosphoproteins and phosphoamino acids as substrates. We hypothesize that AtPAP25 plays a key signaling role during Pi deprivation by functioning as a phosphoprotein phosphatase rather than as a non-specific scavenger of Pi from extracellular P-monoesters.

DOI： 10.1111/tpj.12663

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10967-012-2130-2

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Other Link： http://orcid.org/0000-0001-7545-2771

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC  

Ionic nutrition is essential for plant development. Many techniques have been developed to image and (or) measure ionic movement in plants. Nevertheless, most of them are destructive and limit the analysis. Here, we present the development of radioisotope imaging techniques that overcome such restrictions and allow for real-time imaging of ionic movement. The first system, called macroimaging, was developed to visualize and measure ion uptake and translocation between organs at a whole-plant scale. Such a device is fully compatible with illumination of the sample. We also modified fluorescent microscopes to set up various solutions for ion uptake analysis at the microscopic level. Both systems allow numerical analysis of images and possess a wide dynamic range of detection because they are based on radioactivity.

DOI： 10.1098/rstb.2011.0229

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リアルタイムRIイメージングシステムを搭載したラジオアイソトープ顕微鏡(VIM-micro)を用いて，植物の根における⁵⁵Feの動態を解析した。VIM-microの⁵⁵Feに対する検出感度はイメージングプレートよりも顕著に高く，2分間の積算により，根における⁵⁵Feの分布を可視化できた。10kBq/μLの⁵⁵Feをシロイヌナズナとイネの根の下部側に処理し，その後2時間にわたって60枚の根の画像を取得することで⁵⁵Feの動態を解析した。いずれの植物においても，⁵⁵Feは根の先端部に優先的に分配された。阻害剤の処理，あるいは煮沸によって不活性化した根を，通常の根と比較解析したところ，30分以降に見られる⁵⁵Feの根先端部への蓄積が，生物活性によるものであることが判明した。これらの結果により，Feは，重要なシンク器官である根端部に積極的に輸送されることが示された。

DOI： 10.3769/radioisotopes.61.121

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Walter de Gruyter GmbH  

Abstract

It is very important to visualize the process of nutrient absorption and distribution to study the physiological activity of the plant. We developed a real-time radioisotope (RI) imaging system, where RI tracers were applied to the plant sample. This system allowed the quantitative measurement concerning the uptake of nutrients labeled with radioisotopes, such as ⁴⁵Ca, ³⁵S, ³²P and ¹⁴C as long as several days. The β-rays emitted from the sample were converted to light by a CsI(Tl) scintillator and were guided to a highly sensitive CCD camera. The scintillator surface was covered with an Al plate to avoid LED light penetration but allow selected β-ray penetration. We employed Lotus japonicus for the plant sample and observed the ³²P-phosphate absorption in roots and the accumulation to the aboveground part of the plant. The environment condition of daytime and night was simulated by the ON/OFF of LED timer and the accumulation manner of the ³²P-phosphate in roots and leaves during daytime and night was analyzed. The accumulation of ³²P-phosphate in leaves was highly dependant on light irradiation and higher when the LEDs was turned on, whereas the absorption of ³²P-phosphate in root was higher when the LEDs was turned off. The transfer function concerning the transportation of phosphate within the plant during the developmental stage was obtained from the analysis of ³²P uptake images. We are now trying to get specific moving images of each radioisotope when two kinds of isotopes, such as ³²P and ³⁵S, were applied at the same time to the plant, through an image analysis.

DOI： 10.1524/rcpr.2011.0050

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Other Link： https://www.degruyter.com/document/doi/10.1524/rcpr.2011.0050/html

Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS RESEARCH FOUNDATION  

The main source of phosphorus for plants is inorganic phosphate (Pi), which is characterized by its poor availability and low mobility. Uptake of this element from the soil relies heavily upon the PHT1 transporters, a specific family of plant plasma membrane proteins that were identified by homology with the yeast PH084 Pi transporter. Since the discovery of PHT1 transporters in 1996, various studies have revealed that their function is controlled by a highly complex network of regulation. This review will summarize the current state of research on plant PHT1 multigenic families, including physiological, biochemical, molecular, cellular, and genetics studies.

DOI： 10.3389/fpls.2011.00083

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Publishing type：Research paper (scientific journal)   Publisher：日本アイソトープ協会  

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DOI： 10.1007/s10967-009-0343-9

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植物体の物質動態をリアルタイムで2次元的に解析できれば、植物の物質輸送、シグナル伝達のメカニズムをより詳細に明らかにすることが可能となる。そこで著者らは植物が生きたままの状態で、取り込ませたβ崩壊核種のRI標識化合物をリアルタイムでイメージング可能なシステムを新たに開発した。このリアルタイムオートラジオグラフィーシステムはCsIシンチレータをファイバープレートに蒸着したFOSとシングルフォトンを検出可能な超高感度カメラGaAsP imaging intensifierで構成している。このシステムの解像度(視野5×5cmの場合)はImaging Plateとほぼ同様であったが、単位時間あたりのラジオアイソトープの検出感度は10倍以上の高感度を示した。このシステムを用いた大豆の<SUP>32</SUP>P標識リン酸の吸収過程を画像解析した結果、葉の各部位における経時的な濃度変化の解析結果を解析例として示した。

DOI： 10.3769/radioisotopes.57.287

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DOI： 10.1007/s10967-007-0625-z

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Publisher：The Japanese Society of Plant Physiologists  

We present the identification study of phosphate transporter genes in &lt;I&gt;Lotus japonicus&lt;/I&gt;. mRNA expression of phosphate transpoters in tissues was analyzed by real-time PCR and &lt;I&gt;in situ&lt;/I&gt; hybridization. It was found that, these six phosphate transpoters were expressed in root, leaf, stem, flower and pod with different patterns. Under phosphate starvation condition, expression level was increased in root, leaf, and stem. On the other hand, expression of flower, and pod was the same level as that in control. Especially, in case of LjPT1, LjPT2 and LjPT3 that increased considerably under phosphate starvation in root and leaves.&lt;br&gt;The expression of LjPT1 was increased earlier than these of the other genes in root, whereas LjPT1 and LjPT2 expressions ware increased in matured leaf. The expression of all phosphate transporters was increased in young growing leaf. Then, the amount of phosphate translocation to these tissues was determined by successive &lt;SUP&gt;32&lt;/SUP&gt;P images obtained by real-time imaging system we developed. The amount of phosphate translocation per hour was 5 fold higher in phosphate deficient samples than that in control sample.

DOI： 10.14841/jspp.2009.0.0943.0

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Language：Japanese   Publisher：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.56.0_67

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Language：Japanese   Publisher：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.55.0_78_2

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Publisher：The Japanese Society of Plant Physiologists  

We present the real-time imaging system to image the ion uptake in culture solution to root in dark condition, as well as from root to up-ground part in light condition. Successive imaging from dark to light condition was able to perform for the first time, which is the great advantage of using radioisotopes. A culture solution containing &lt;SUP&gt;32&lt;/SUP&gt;P labeled (500kBq/ml) was supplied to &lt;I&gt;Lotus Japonicus&lt;/I&gt;. To supply sufficient light to the up-ground part, 100 LED was fixed at the up-ground part of the sample holder. The beta-rays emitted from the sample was converted to light by a CsI scintillator and was guided to a CCD camera. The image was accumulated every 3 minutes for 40 to 60 hours. The accumulation rate of &lt;SUP&gt;32&lt;/SUP&gt;P in root was rather constant, whereas in leaves, the rate was increased during day and decreased at night.

DOI： 10.1007/s10967-009-0344-8

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Event date： 2023.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Photosynthetic organisms acquire light as an energy source and take in elements as materials. Iron, which forms the light environment of our "green sea" hypothesis, also affects the amount of phosphorus available to organisms. Previous studies have reported that phosphorus was low in the early terrestrial environment and increased after about 800 million years ago, but there are many theories about the age for which there is little fossil or geological information. Therefore, from the viewpoint of the coevolution of the earth and life, we hypothesized that traces reflecting the earth's environment at that time might remain in the evolution of phosphorus utilization mechanisms on the life side. Based on structural and phylogenetic analysis of phosphorus membrane transporter proteins responsible for phosphorus uptake and comparison of literature information, we confirmed that cyanobacteria and algae that have existed since the primitive Earth have mechanisms that respond to low concentrations of phosphorus, while higher plants have mechanisms that respond to high concentrations of phosphorus. We will present data that support the low-phosphorus theory of the primitive Earth from an examination of the evolution of living organisms.

Event date： 2022.9

Language：English   Presentation type：Symposium, workshop panel (public)  

Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Symposium, workshop panel (nominated)  

Venue：淡路国際会議場   Country：Japan  

Event date： 2022.3 - 2023.3

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Venue：つくば国際会議場   Country：Japan  

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Event date： 2022.3

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Venue：つくば国際会議場   Country：Japan  

Event date： 2021.7

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Venue：オンライン   Country：Japan  

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Event date： 2019.3

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Venue：Nagoya University   Country：Japan  

Event date： 2019.3

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Venue：名古屋大学   Country：Japan  

Event date： 2018.10

Language：English   Presentation type：Symposium, workshop panel (nominated)  

Country：Japan  

Event date： 2018.1

Language：English   Presentation type：Oral presentation (general)  

Country：France