Verified email at riken.jp
Unit Leader, Environmental Response Research Unit
RIKEN Center for Sustainable Resource Science
Chang-Jin Park and Ryoung Shin
Frontiers in Plant Science, eISSN: 1664462X, Published: 8 September 2022 Frontiers Media SA
Calcium (Ca2+) serves as a ubiquitous second messenger by mediating various signaling pathways and responding to numerous environmental conditions in eukaryotes. Therefore, plant cells have developed complex mechanisms of Ca2+ communication across the membrane, receiving the message from their surroundings and transducing the information into cells and organelles. A wide range of biotic and abiotic stresses cause the increase in [Ca2+]cyt as a result of the Ca2+ influx permitted by membrane-localized Ca2+ permeable cation channels such as CYCLIC NUCLEOTIDE-GATE CHANNELs (CNGCs), and voltage-dependent HYPERPOLARIZATION-ACTIVATED CALCIUM2+ PERMEABLE CHANNELs (HACCs), as well as GLUTAMATE RECEPTOR-LIKE RECEPTORs (GLRs) and TWO-PORE CHANNELs (TPCs). Recently, resistosomes formed by some NUCLEOTIDE-BINDING LEUCINE-RICH REPEAT RECEPTORs (NLRs) are also proposed as a new type of Ca2+ permeable cation channels. On the contrary, some Ca2+ transporting membrane proteins, mainly Ca2+-ATPase and Ca2+/H+ exchangers, are involved in Ca2+ efflux for removal of the excessive [Ca2+]cyt in order to maintain the Ca2+ homeostasis in cells. The Ca2+ efflux mechanisms mediate the wide ranges of cellular activities responding to external and internal stimuli. In this review, we will summarize and discuss the recent discoveries of various membrane proteins involved in Ca2+ influx and efflux which play an essential role in fine-tuning the processing of information for plant responses to abiotic and biotic stresses.
Hyeran Moon, Young-Ah Kim, Ryoung Shin, and Chang-Jin Park
Rice Science, ISSN: 16726308, Pages: 225-236, Published: May 2022 Elsevier BV
Ju Yeon Moon, Takae Miyazaki, Makoto Muroi, Nobomoto Watanabe, and Ryoung Shin
Methods in Enzymology, ISSN: 00766879, eISSN: 15577988, Published: 2022 Elsevier
Ju Yeon Moon, Eri Adams, Takae Miyazaki, Yasumitsu Kondoh, Makoto Muroi, Nobumoto Watanabe, Hiroyuki Osada, and Ryoung Shin
Scientific Reports, eISSN: 20452322, Published: December 2021 Springer Science and Business Media LLC
AbstractCesium (Cs) is found at low levels in nature but does not confer any known benefit to plants. Cs and K compete in cells due to the chemical similarity of Cs to potassium (K), and can induce K deficiency in cells. In previous studies, we identified chemicals that increase Cs tolerance in plants. Among them, a small chemical compound (C17H19F3N2O2), named CsToAcE1, was confirmed to enhance Cs tolerance while increasing Cs accumulation in plants. Treatment of plants with CsToAcE1 resulted in greater Cs and K accumulation and also alleviated Cs-induced growth retardation in Arabidopsis. In the present study, potential target proteins of CsToAcE1 were isolated from Arabidopsis to determine the mechanism by which CsToAcE1 alleviates Cs stress, while enhancing Cs accumulation. Our analysis identified one of the interacting target proteins of CsToAcE1 to be BETA-GLUCOSIDASE 23 (AtβGLU23). Interestingly, Arabidopsis atβglu23 mutants exhibited enhanced tolerance to Cs stress but did not respond to the application of CsToAcE1. Notably, application of CsToAcE1 resulted in a reduction of Cs-induced AtβGLU23 expression in wild-type plants, while this was not observed in a high affinity transporter mutant, athak5. Our data indicate that AtβGLU23 regulates plant response to Cs stress and that CsToAcE1 enhances Cs tolerance by repressing AtβGLU23. In addition, AtHAK5 also appears to be involved in this response.
Takae Miyazaki, Ju Yeon Moon, and Ryoung Shin
Plant Biotechnology Reports, ISSN: 18635466, eISSN: 18635474, Pages: 349-357, Published: June 2021 Springer Science and Business Media LLC
Amirah Mohammad-Sidik, Jian Sun, Ryoung Shin, Zhizhong Song, Youzheng Ning, Elsa Matthus, Katie A. Wilkins, and Julia M. Davies
International Journal of Molecular Sciences, ISSN: 16616596, eISSN: 14220067, Pages: 1-20, Published: 2 January 2021 MDPI AG
Extracellular ATP (eATP) has long been established in animals as an important signalling molecule but this is less understood in plants. The identification of Arabidopsis thaliana DORN1 (Does Not Respond to Nucleotides) as the first plant eATP receptor has shown that it is fundamental to the elevation of cytosolic free Ca2+ ([Ca2+]cyt) as a possible second messenger. eATP causes other downstream responses such as increase in reactive oxygen species (ROS) and nitric oxide, plus changes in gene expression. The plasma membrane Ca2+ influx channels involved in eATP-induced [Ca2+]cyt increase remain unknown at the genetic level. Arabidopsis thaliana Annexin 1 has been found to mediate ROS-activated Ca2+ influx in root epidermis, consistent with its operating as a transport pathway. In this study, the loss of function Annexin 1 mutant was found to have impaired [Ca2+]cyt elevation in roots in response to eATP or eADP. Additionally, this annexin was implicated in modulating eATP-induced intracellular ROS accumulation in roots as well as expression of eATP-responsive genes.
Cation Transporters in Plants, Pages: 437-453, Published: 1 January 2021 Elsevier
Eri Adams, Takae Miyazaki, Ju Yeon Moon, Yuji Sawada, Muneo Sato, Kiminori Toyooka, Masami Yokota Hirai, and Ryoung Shin
International Journal of Molecular Sciences, ISSN: 16616596, eISSN: 14220067, Pages: 1-17, Published: 1 December 2020 MDPI AG
Syringic acid, a phenolic compound, serves a variety of beneficial functions in cells. Syringic acid increases in plants in response to cesium, and exogenous application of syringic acid resulted in a significant attenuation of cesium-induced growth defects in Arabidopsis. In addition, cesium or syringic acid application to plants also resulted in increased lignin deposition in interfascicular fibers. To better understand the role of lignin and syringic acid in attenuating cesium-induced growth defects, two mutants for Arabidopsis REDUCED EPIDERMAL FLUORESCENE 4 (REF4) and fourteen laccase mutants, some of which have lower levels of lignin, were evaluated for their response to cesium. These mutants responded differently to cesium stress, compared to control plants, and the application of syringic acid alleviated cesium-induced growth defects in the laccase mutants but not in the ref4 mutants. These findings imply that lignin plays a role in cesium signaling but the attenuation of cesium stress defects by syringic acid is mediated by regulatory components of lignin biosynthesis and not lignin biosynthesis itself. In contrast, syringic acid did not alleviate any low potassium-induced growth defects. Collectively, our findings provide the first established link between lignin and cesium stress via syringic acid in plants.
Eri Adams, Takae Miyazaki, Shunsuke Watanabe, Naoko Ohkama-Ohtsu, Mitsunori Seo, and Ryoung Shin
Frontiers in Plant Science, eISSN: 1664462X, Published: 21 January 2020 Frontiers Media SA
Phytoremediation is optimized when plants grow vigorously while accumulating the contaminant of interest. Here we show that sulphur supply alleviates aerial chlorosis and growth retardation caused by cesium stress without reducing cesium accumulation in Arabidopsis thaliana. This alleviation was not due to recovery of cesium-induced potassium decrease in plant tissues. Sulphur supply also alleviated sodium stress but not potassium deficiency stress. Cesium-induced root growth inhibition has previously been demonstrated as being mediated through jasmonate biosynthesis and signalling but it was found that sulphur supply did not decrease the levels of jasmonate accumulation or jasmonate-responsive transcripts. Instead, induction of a glutathione synthetase gene GSH2 and reduction of a phytochelatin synthase gene PCS1 as well as increased accumulation of glutathione and cysteine were observed in response to cesium. Exogenous application of glutathione or concomitant treatments of its biosynthetic intermediates indeed alleviated cesium stress. Interestingly, concomitant treatments of glutathione biosynthetic intermediates together with a glutathione biosynthesis inhibitor did not cancel the alleviatory effects against cesium suggesting the existence of a glutathione-independent pathway. Taken together, our findings demonstrate that plants exposed to cesium increase glutathione accumulation to alleviate the deleterious effects of cesium and that exogenous application of sulphur-containing compounds promotes this innate process.
Ju Moon, Célestine Belloeil, Madeline Ianna, and Ryoung Shin
International Journal of Molecular Sciences, ISSN: 16616596, eISSN: 14220067, Published: 2 January 2019 MDPI AG
Heavy metal ions, including toxic concentrations of essential ions, negatively affect diverse metabolic and cellular processes. Heavy metal ions are known to enter cells in a non-selective manner; however, few studies have examined the regulation of heavy metal ion transport. Plant cyclic nucleotide-gated channels (CNGCs), a type of Ca2+-permeable-channel, have been suggested to be involved in the uptake of both essential and toxic cations. To determine the candidates responsible for heavy metal ion transport, a series of Arabidopsis CNGC mutants were examined for their response to Pb2+ and Cd2+ ions. The primary focus was on root growth and the analysis of the concentration of heavy metals in plants. Results, based on the analysis of primary root length, indicated that AtCNGC1, AtCNGC10, AtCNGC13 and AtCNGC19 play roles in Pb2+ toxicity, while AtCNGC11, AtCNGC13, AtCNGC16 and AtCNGC20 function in Cd2+ toxicity in Arabidopsis. Ion content analysis verified that the mutations of AtCNGC1 and AtCNGC13 resulted in reduced Pb2+ accumulation, while the mutations of AtCNGC11, AtCNGC15 and AtCNGC19 resulted in less Pb2+ and Cd2+ accumulation in plants. These findings provide functional evidence which support the roles of these AtCNGCs in the uptake and transport of Pb2+ or Cd2+ ion in plants.
Eri Adams, Takae Miyazaki, and Ryoung Shin
Plant Signaling and Behavior, ISSN: 15592316, eISSN: 15592324, Published: 2 January 2019 Informa UK Limited
ABSTRACT Cesium has no known beneficial effects on plants and while plants have the ability to absorb it through the root system, plant growth is retarded at high concentrations. Recently, we have shown that potassium influx through a potassium channel complex AKT1-KC1 is inhibited by cesium in Arabidopsis thaliana and the resultant reduction in potassium accumulation in the plant is the primary cause of retarded growth. By contrast, a major potassium transporter, HAK5 whose function is crucial under potassium deficiency, was found to be either not affected or complementary under cesium stress in the low affinity potassium range. Here we show the effects of insertional mutation on other members of KUP/HAK/KT gene family in response to cesium stress. Potassium and cesium concentrations in each mutant line demonstrated that disruption of a single KUP/HAK/KT gene was not sufficient to significantly reduce potassium/cesium accumulation, suggesting a complementary effect among these KUP (K+ UPTAKE PERMEASE) transporters.
Eri Adams, Takae Miyazaki, Shunya Saito, Nobuyuki Uozumi, and Ryoung Shin
Plant and Cell Physiology, ISSN: 00320781, eISSN: 14719053, Pages: 63-76, Published: 1 January 2019 Oxford University Press (OUP)
Cesium (Cs+) is known to compete with the macronutrient potassium (K+) inside and outside of plants and to inhibit plant growth at high concentrations. However, the detailed molecular mechanisms of how Cs+ exerts its deleterious effects on K+ accumulation in plants are not fully elucidated. Here, we show that mutation in a member of the major K+ channel AKT1-KC1 complex renders Arabidopsis thaliana hypersensitive to Cs+. Higher severity of the phenotype and K+ loss were observed for these mutants in response to Cs+ than to K+ deficiency. Electrophysiological analysis demonstrated that Cs+, but not sodium, rubidium or ammonium, specifically inhibited K+ influx through the AKT1-KC1 complex. In contrast, Cs+ did not inhibit K+ efflux through the homomeric AKT1 channel that occurs in the absence of KC1, leading to a vast loss of K+. Our observation suggests that reduced K+ accumulation due to blockage/competition in AKT1 and other K+ transporters/channels by Cs+ plays a major role in plant growth retardation. This report describes the mechanical role of Cs+ in K+ accumulation, and in turn in plant performance, providing actual evidence at the plant level for what has long been believed, i.e. K+ channels are, therefore AKT1 is, 'blocked' by Cs+.
Eri Adams, Koji Mikami, and Ryoung Shin
Journal of Applied Phycology, ISSN: 09218971, eISSN: 15735176, Pages: 2617-2626, Published: 1 October 2017 Springer Science and Business Media LLC
Seaweeds are believed to have developed unique mechanisms to maintain optimal cellular potassium and sodium concentrations in order to survive in the saline marine environment. To gain a molecular understanding of underlying potassium/sodium homeostasis in seaweeds, full-length cDNA libraries from the multiple stages in the life cycle, including gametophytes, conchosporangia and sporophytes of a marine red alga, Pyropia yezoensis, were constructed. A large portion of genes from each library through the life cycle was revealed to be functionally unknown reconfirming the uniqueness of P. yezoensis genes in terms of evolutionary lineage. Genes that could potentially contribute to potassium deficiency tolerance were selected from the potassium uptake defective Escherichia coli strain expressing gametophytes and conchosporangia libraries under the low potassium conditions. Of those, an ammonium transporter gene, PyAMT1, was demonstrated to enhance potassium deficiency tolerance effectively when expressed in the E. coli strain. Potential roles of PyAMT1 and other candidate components in this context are discussed.
Hajime Takiguchi, Jong-Pil Hong, Hidetoshi Nishiyama, Makoto Hakata, Hidemitsu Nakamura, Hiroaki Ichikawa, Chang-Jin Park, and Ryoung Shin
Plant Molecular Biology Reporter, ISSN: 07359640, eISSN: 15729818, Pages: 343-354, Published: 1 June 2017 Springer Science and Business Media LLC
Nitrogen is the most critical nutrient for plant growth. To find potential strategies for enhancing both nitrogen use and tolerance to nitrogen deficiency in rice plants, we used the rice Full-length-cDNA OvereXpressor (FOX)-hunting system, a high-throughput phenotyping screen. After screening 3229 rice FOX lines, we identified 82 FOX-hunting lines that responded differently to nitrogen starvation. Among them, 11 FOX-hunting lines overexpressed putative E3 ligases, of which 6 were RING-type and 5 were F-box type E3 ligases. Of these, two lines overexpressed the same F-box type E3 ligase, OsFBL15. In vitro ubiquitination assay confirmed the auto-ubiquitination activity of OsFBL15. The overexpression of these E3 ligases altered the rice response to nitrogen deficiency and suggests a way to develop rice that is tolerant to nitrogen-deficient field conditions.
Jong-Pil Hong, Eri Adams, Yuki Yanagawa, Minami Matsui, and Ryoung Shin
Biochemical and Biophysical Research Communications, ISSN: 0006291X, eISSN: 10902104, Volume: 485, Pages: 174-180, Published: 25 March 2017 Elsevier BV
14-3-3 proteins regulate numerous cellular processes through interaction with their target proteins in a phosphorylation dependent manner. Although proteins that are regulated by 14-3-3s have been studied, the regulatory mechanism of 14-3-3s is poorly understood. In the present study, F-box proteins, a component of Skp1-Cullin-F-box E3 ubiquitin ligase, were identified as 14-3-3 targets using yeast two-hybrid screening. Among them, AtSKIP18 and AtSKIP31, were shown to mediate the degradation of Arabidopsis 14-3-3s. Mutational analyses of AtSKIP18 and AtSKIP31 indicated that the phosphorylation of AtSKIPs is critical for interaction and degradation of 14-3-3s. The loss-of-function mutation in AtSKIP31 resulted in enhanced primary root growth under nitrogen deficient conditions. These findings suggest that AtSKIP31 regulates the primary root growth in nitrogen deficiency via degrading 14-3-3s.
Eri Adams, Takae Miyazaki, Aya Hayaishi-Satoh, Minwoo Han, Miyako Kusano, Himanshu Khandelia, Kazuki Saito, and Ryoung Shin
Scientific Reports, eISSN: 20452322, Published: 23 February 2017 Springer Science and Business Media LLC
Phytoaccumulation is a technique to extract metals from soil utilising ability of plants. Cesium is a valuable metal while radioactive isotopes of cesium can be hazardous. In order to establish a more efficient phytoaccumulation system, small molecules which promote plants to accumulate cesium were investigated. Through chemical library screening, 14 chemicals were isolated as ‘cesium accumulators’ in Arabidopsis thaliana. Of those, methyl cysteinate, a derivative of cysteine, was found to function within the plant to accumulate externally supplemented cesium. Moreover, metabolite profiling demonstrated that cesium treatment increased cysteine levels in Arabidopsis. The cesium accumulation effect was not observed for other cysteine derivatives or amino acids on the cysteine metabolic pathway tested. Our results suggest that methyl cysteinate, potentially metabolised from cysteine, binds with cesium on the surface of the roots or inside plant cells and improve phytoaccumulation.
Plant Macronutrient Use Efficiency: Molecular and Genomic Perspectives in Crop Plants, Pages: 149-163, Published: 1 January 2017 Elsevier
Potassium is a macronutrient that is essential for plant growth and development. The availability of the potassium, not its absolute level, is often restricted in soils, thus dramatically diminishing crop yield and quality. Therefore, understanding how plants sense potassium deficiency and activate their potassium uptake system is a prerequisite for strategically improving potassium use efficiency in plants. Recent progress has drawn attention to the mechanisms that signal potassium deficiency, that regulate potassium uptake, and that transport potassium in plants. This chapter summarizes three major topics: (1) potassium transport mechanisms, (2) regulatory components of potassium uptake and potassium deficiency signaling, and (3) strategies to improve potassium use efficiency in plants.
Ryoung Shin and Eri Adams
Impact of Cesium on Plants and the Environment, Pages: 101-124, Published: 1 January 2016 Springer International Publishing
Radiocesium is mainly generated through anthropogenic activities and poses a great threat to health and the environment. As an alternative to costly physical and chemical methods to remediate the contaminated soil and water, phytoremediation, a technique making use of plants to remove or stabilise contamination, is receiving increasing attention. Selection of plant species that accumulate high levels of radiocesium has, therefore, been intensively investigated. In recent years, molecular techniques have enabled researchers to elucidate cesium transporters and regulatory mechanisms through which cesium uptake occurs in plants. Some proteins have been predicted to mediate cesium and many players, including cations and phytohormones, have been suggested as regulators. Although the molecular understanding of cesium uptake in plants is only just being revealed, the knowledge can readily be applied to radiocesium phytoremediation. In parallel, efforts to improve phytoremediation efficiency have sought the aid of biotic and abiotic factors such as microorganisms and chemicals. In this chapter, findings on the molecular mechanisms and regulation of cesium uptake in plants, what is known and what needs to be researched, are discussed. Then follows a discussion of the plant species suitable for radiocesium phytoremediation and the factors which improve phytoremediation efficiency.
Eri Adams, Vitaly Chaban, Himanshu Khandelia, and Ryoung Shin
Scientific Reports, eISSN: 20452322, Published: 2015 Springer Science and Business Media LLC
High concentrations of cesium (Cs+) inhibit plant growth but the detailed mechanisms of Cs+ uptake, transport and response in plants are not well known. In order to identify small molecules with a capacity to enhance plant tolerance to Cs+, chemical library screening was performed using Arabidopsis. Of 10,000 chemicals tested, five compounds were confirmed as Cs+ tolerance enhancers. Further investigation and quantum mechanical modelling revealed that one of these compounds reduced Cs+ concentrations in plants and that the imidazole moiety of this compound bound specifically to Cs+. Analysis of the analogous compounds indicated that the structure of the identified compound is important for the effect to be conferred. Taken together, Cs+ tolerance enhancer isolated here renders plants tolerant to Cs+ by inhibiting Cs+ entry into roots via specific binding to the ion thus, for instance, providing a basis for phytostabilisation of radiocesium-contaminated farmland.
Eri Adams, Celine Diaz, Jong-Pil Hong, and Ryoung Shin
International Journal of Molecular Sciences, ISSN: 16616596, eISSN: 14220067, Pages: 22801-22814, Published: 9 December 2014 MDPI AG
14-3-3 proteins are regulatory proteins found in all eukaryotes and are known to selectively interact with phosphorylated proteins to regulate physiological processes. Through an affinity purification screening, many light-related proteins were recovered as 14-3-3 candidate binding partners. Yeast two-hybrid analysis revealed that the 14-3-3 kappa isoform (14-3-3κ) could bind to PHYTOCHROME INTERACTING FACTOR3 (PIF3) and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). Further analysis by in vitro pull-down assay confirmed the interaction between 14-3-3κ and PIF3. Interruption of putative phosphorylation sites on the 14-3-3 binding motifs of PIF3 was not sufficient to inhibit 14-3-3κ from binding or to disturb nuclear localization of PIF3. It was also indicated that 14-3-3κ could bind to other members of the PIF family, such as PIF1 and PIF6, but not to LONG HYPOCOTYL IN FAR-RED1 (HFR1). 14-3-3 mutants, as well as the PIF3 overexpressor, displayed longer hypocotyls, and a pif3 mutant displayed shorter hypocotyls than the wild-type in red light, suggesting that 14-3-3 proteins are positive regulators of photomorphogenesis and function antagonistically with PIF3. Consequently, our results indicate that 14-3-3 proteins bind to PIFs and initiate photomorphogenesis in response to a light signal.
Masaaki Akamatsu, Hirokazu Komatsu, Taizo Mori, Eri Adams, Ryoung Shin, Hideki Sakai, Masahiko Abe, Jonathan P. Hill, and Katsuhiko Ariga
ACS Applied Materials and Interfaces, ISSN: 19448244, eISSN: 19448252, Pages: 8208-8211, Published: 11 June 2014 American Chemical Society (ACS)
The accident at the Fukushima Daiichi nuclear power plant, which was one of the most serious adverse effects of the Great East Japan Earthquake, was accompanied by the release of a large quantity of radioactive materials including (137)Cs to the environment. In a previous report, we developed and proposed a cesium (Cs) fluorescent probe, "Cesium Green", that enables the detection of cesium carbonate particles by spraying an alcoholic solution of the Cesium Green probe. In this paper, the sensing activity of this probe was investigated for its selectivity (by using an optode method) and for its application to detect micrometer-sizes Cs particles. Cesium Green was also assessed for its use in plant cellular imaging of Cs localization in Arabidopsis. Cesium Green enabled high-resolution Cs imaging of Cs-containing particles and of Cs contained in plants.
Molecules and Cells, ISSN: 10168478, eISSN: 02191032, Pages: 575-584, Published: 2014 Korean Society for Molecular and Cellular Biology
Potassium is a macronutrient that is crucial for healthy plant growth. Potassium availability, however, is often limited in agricultural fields and thus crop yields and quality are reduced. Therefore, improving the efficiency of potassium uptake and transport, as well as its utilization, in plants is important for agricultural sustainability. This review summarizes the current knowledge on the molecular mechanisms involved in potassium uptake and transport in plants, and the molecular response of plants to different levels of potassium availability. Based on this information, four strategies for improving potassium use efficiency in plants are proposed; 1) increased root volume, 2) increasing efficiency of potassium uptake from the soil and translocation in planta, 3) increasing mobility of potassium in soil, and 4) molecular breeding new varieties with greater potassium efficiency through marker assisted selection which will require identification and utilization of potassium associated quantitative trait loci.
Eri Adams and Ryoung Shin
Journal of Integrative Plant Biology, ISSN: 16729072, eISSN: 17447909, Pages: 231-249, Published: March 2014 Wiley
Potassium (K⁺) is an essential macronutrient in plants and a lack of K⁺ significantly reduces the potential for plant growth and development. By contrast, sodium (Na⁺), while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of K⁺ can be undertaken by Na⁺ but K⁺ homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of K⁺ and Na⁺ transport and signaling in plants. This review summarizes three major topics: (i) the transport mechanisms of K⁺ and Na⁺ from the soil to the shoot and to the cellular compartments; (ii) the mechanisms through which plants sense and respond to K⁺ and Na⁺ availability; and (iii) the components involved in maintenance of K⁺/Na⁺ homeostasis in plants under salt stress.
Jong-Pil Hong, Yoshizumi Takeshi, Youichi Kondou, Daniel P. Schachtman, Minami Matsui, and Ryoung Shin
Plant and Cell Physiology, ISSN: 00320781, eISSN: 14719053, Pages: 1478-1490, Published: September 2013 Oxford University Press (OUP)
Potassium (K) is an essential macronutrient for plant growth and reproduction. HAK5, an Arabidopsis high-affinity K transporter gene, plays an important role in K uptake. Its expression is up-regulated in response to K deprivation and is rapidly down-regulated when sufficient K levels have been re-established. To identify transcription factors regulating HAK5, an Arabidopsis TF FOX (Transcription Factor Full-length cDNA Over-eXpressor) library containing approximately 800 transcription factors was used to transform lines previously transformed with a luciferase reporter gene whose expression was driven by the HAK5 promoter. When grown under sufficient K levels, 87 lines with high luciferase activity were identified, and endogenous HAK5 expression was confirmed in 27 lines. Four lines overexpressing DDF2 (Dwarf and Delayed Flowering 2), JLO (Jagged Lateral Organs), TFII_A (Transcription initiation Factor II_A gamma chain) and bHLH121 (basic Helix-Loop-Helix 121) were chosen for further characterization by luciferase activity, endogenous HAK5 level and root growth in K-deficient conditions. Further analysis showed that the expression of these transcription factors increased in response to low K and salt stress. In comparison with controls, root growth under low K conditions was better in each of these four TF FOX lines. Activation of HAK5 expression by these four transcription factors required at least 310 bp of upstream sequence of the HAK5 promoter. These results indicate that at least these four transcription factors can bind to the HAK5 promoter in response to K limitation and activate HAK5 expression, thus allowing plants to adapt to nutrient stress.
Chang-Jin Park, K. J. Kim, R. Shin, J. M. Park, Y. C. Shin and K. H. Paek
Plant Journal, ISSN: 09607412, eISSN: 1365313X, Pages: 890, Published: September 2013 Wiley