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Hideyuki Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Correction to: Molecular mechanisms mediating root Hydrotropism: what we have observed since the rediscovery of Hydrotropism
Journal of Plant Research, 2020Co-Authors: Yutaka Miyazawa, Hideyuki TakahashiAbstract:The article Molecular mechanisms mediating root Hydrotropism
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Molecular mechanisms mediating root Hydrotropism: what we have observed since the rediscovery of Hydrotropism
Journal of Plant Research, 2020Co-Authors: Yutaka Miyazawa, Hideyuki TakahashiAbstract:Roots display directional growth toward moisture in response to a water potential gradient. Root Hydrotropism is thought to facilitate plant adaptation to continuously changing water availability. Hydrotropism has not been as extensively studied as gravitropism. However, comparisons of hydrotropic and gravitropic responses identified mechanisms that are unique to Hydrotropism. Regulatory mechanisms underlying the hydrotropic response appear to differ among different species. We recently performed molecular and genetic analyses of root Hydrotropism in Arabidopsis thaliana . In this review, we summarize the current knowledge of specific mechanisms mediating root Hydrotropism in several plant species.
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Plasma Membrane-Associated Ca2+-Binding Protein PCaP1 is Involved in Root Hydrotropism of Arabidopsis thaliana
Plant and Cell Physiology, 2019Co-Authors: Natsuki Tanaka-takada, Akie Kobayashi, Hideyuki Takahashi, Takehiro Kamiya, Toshinori Kinoshita, Masayoshi MaeshimaAbstract:Root Hydrotropism is an essential growth response to water potential gradients in plants. To understand the mechanism, fundamental elements such as MIZU-KUSSEI 1 (MIZ1) have been investigated extensively. We investigated the physiological role of a plasma membrane-associated cation-binding protein (PCaP1) and examined the effect of PCaP1 loss-of-function mutations on root Hydrotropism. pcap1 knockout mutants showed a defect in root bending as a hydrotropic response, although gravitropism was normal in pcap1 mutants. When pcap1 seedlings were treated with abscisic acid, a negative regulator of gravitropism, the seedlings showed normal gravitropism. The Hydrotropism defect in pcap1 mutants was clearly rescued by introducing the genomic sequence of PCaP1 with an endodermis-specific promoter. Analysis of PCaP1-greenfluorescent protein-expressing roots by confocal laser scanning microscopy revealed that PCaP1 was stably associated with the plasma membrane in most cells, but in the cytoplasm of endodermal cells at the bending region. Furthermore, we prepared a transgenic line overexpressing MIZ1 on the pcap1 background and found that the pcap1 Hydrotropism defect was rescued. Our results indicate that PCaP1 in the endodermal cells of the root elongation zone is involved in the hydrotropic response. We suggest that PCaP1 contributes to Hydrotropism through a MIZ1-independent pathway or as one of the upstream components that transduce water potential signals to MIZ1.
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Auxin transport and response requirements for root Hydrotropism differ between plant species.
Journal of Experimental Botany, 2017Co-Authors: Yusuke Nakajima, Yoshitaka Nara, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Nobuharu Fujii, Hideyuki TakahashiAbstract:: The direction of auxin transport changes in gravistimulated roots, causing auxin accumulation in the lower side of horizontally reoriented roots. This study found that auxin was similarly involved in Hydrotropism and gravitropism in rice and pea roots, but Hydrotropism in Lotus japonicus roots was independent of both auxin transport and response. Application of either auxin transport inhibitors or an auxin response inhibitor decreased both Hydrotropism and gravitropism in rice roots, and reduced Hydrotropism in pea roots. However, Lotus roots treated with these inhibitors showed reduced gravitropism but an unaltered or an enhanced hydrotropic response. Inhibiting auxin biosynthesis substantially reduced both tropisms in rice and Lotus roots. Removing the final 0.2 mm (including the root cap) from the root tip inhibited gravitropism but not Hydrotropism in rice seedling roots. These results suggested that modes of auxin involvement in Hydrotropism differed between plant species. In rice roots, although auxin transport and responses were required for both gravitropism and Hydrotropism, the root cap was involved in the auxin regulation of gravitropism but not Hydrotropism. Hydrotropism in Lotus roots, however, may be regulated by a novel mechanism that is independent of both auxin transport and the TIR1/AFBs auxin response pathway.
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GNOM regulates root Hydrotropism and phototropism independently of PIN-mediated auxin transport.
Plant Science, 2014Co-Authors: Teppei Moriwaki, Yutaka Miyazawa, Nobuharu Fujii, Hideyuki TakahashiAbstract:Plant roots exhibit tropisms in response to gravity, unilateral light and moisture gradients. During gravitropism, an auxin gradient is established by PIN auxin transporters, leading to asymmetric growth. GNOM, a guanine nucleotide exchange factor of ARF GTPase (ARF-GEF), regulates PIN localization by regulating subcellular trafficking of PINs. Therefore, GNOM is important for gravitropism. We previously isolated mizu-kussei2 (miz2), which lacks hydrotropic responses; MIZ2 is allelic to GNOM. Since PIN proteins are not required for root Hydrotropism in Arabidopsis, the role of GNOM in root Hydrotropism should differ from that in gravitropism. To examine this possibility, we conducted genetic analysis of gnom(miz2) and gnom trans-heterozygotes. The mutant gnom(miz2), which lacks hydrotropic responses, was partially recovered by gnom(emb30-1), which lacks GEF activity, but not by gnom(B4049), which lacks heterotypic domain interactions. Furthermore, the phototropic response of gnom trans-heterozygotes differed from that of the pin2 mutant allele eir1-1. Moreover, defects in the polarities of PIN2 and auxin distribution in a severe gnom mutant were recovered by gnom(miz2). Therefore, an unknown GNOM-mediated vesicle trafficking system may mediate root Hydrotropism and phototropism independently of PIN trafficking.
Nobuharu Fujii - One of the best experts on this subject based on the ideXlab platform.
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Root-tip-mediated inhibition of Hydrotropism is accompanied with the suppression of asymmetric expression of auxin-inducible genes in response to moisture gradients in cucumber roots.
PLOS ONE, 2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:In cucumber seedlings, gravitropism interferes with Hydrotropism, which results in the nearly complete inhibition of Hydrotropism under stationary conditions. However, hydrotropic responses are induced when the gravitropic response in the root is nullified by clinorotation. Columella cells in the root cap sense gravity, which induces the gravitropic response. In this study, we found that removing the root tip induced Hydrotropism in cucumber roots under stationary conditions. The application of auxin transport inhibitors to cucumber seedlings under stationary conditions suppressed the hydrotropic response induced by the removal of the root tip. To investigate the expression of genes related to Hydrotropism in de-tipped cucumber roots, we conducted transcriptome analysis of gene expression by RNA-Seq using seedlings exhibiting hydrotropic and gravitropic responses. Of the 21 and 45 genes asymmetrically expressed during hydrotropic and gravitropic responses, respectively, five genes were identical. Gene ontology (GO) analysis indicated that the category auxin-inducible genes was significantly enriched among genes that were more highly expressed in the concave side of the root than the convex side during hydrotropic or gravitropic responses. Reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR) analysis revealed that root Hydrotropism induced under stationary conditions (by removing the root tip) was accompanied by the asymmetric expression of several auxin-inducible genes. However, intact roots did not exhibit the asymmetric expression patterns of auxin-inducible genes under stationary conditions, even in the presence of a moisture gradient. These results suggest that the root tip inhibits Hydrotropism by suppressing the induction of asymmetric auxin distribution. Auxin transport and distribution not mediated by the root tip might play a role in Hydrotropism in cucumber roots.
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Effects of root tip removal on root Hydrotropism in cucumber seedlings.
2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:(A–B) Effects of root tip removal on root gravitropism in cucumber seedlings. 24-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were placed in a vertical or horizontal position. After 1 h, root curvature (A) and length (B) were measured. Experiments (using eight seedlings) were repeated three times, and the mean ± SE was calculated. (C–E) Effects of root tip removal on root Hydrotropism in cucumber seedlings. 18-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were exposed to a moisture gradient induced by K2CO3. After incubation under stationary conditions for 4 h and 9 h or in a 3D clinostat for 9 h, root curvature (C) and length (D) were measured. Experiments (using seven seedlings) were repeated three times, and the mean ± SE was calculated. Different letters indicate statistically significant differences (P
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gravitropism interferes with Hydrotropism via counteracting auxin dynamics in cucumber roots clinorotation and spaceflight experiments
New Phytologist, 2017Co-Authors: Keita Morohashi, Miki Okamoto, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Yutaka Miyazawa, Nobuharu Fujii, Toru ShimazuAbstract:Summary Roots of land plants show gravitropism and Hydrotropism in response to gravity and moisture gradients, respectively, for controlling their growth orientation. Gravitropism interferes with Hydrotropism, although the mechanistic aspects are poorly understood. Here, we differentiated Hydrotropism from gravitropism in cucumber roots by conducting clinorotation and spaceflight experiments. We also compared mechanisms regulating Hydrotropism and auxin-regulated gravitropism. Clinorotated or microgravity (μG)-grown cucumber seedling roots hydrotropically bent toward wet substrate in the presence of moisture gradients, but they grew straight in the direction of normal gravitational force at the Earth's surface (1G) on the ground or centrifuge-generated 1G in space. The roots appeared to become hydrotropically more sensitive to moisture gradients under μG conditions in space. Auxin transport inhibitors significantly reduced the hydrotropic response of clinorotated seedling roots. The auxin efflux protein CsPIN5 was differentially expressed in roots of both clinorotated and μG-grown seedlings; with higher expression in the high-humidity (concave) side than the low-humidity (convex) side of hydrotropically responding roots. Our results suggest that roots become hydrotropically sensitive in μG, and CsPIN5-mediated auxin transport has an important role in inducing root Hydrotropism. Thus, hydrotropic and gravitropic responses in cucumber roots may compete via differential auxin dynamics established in response to moisture gradients and gravity.
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Auxin transport and response requirements for root Hydrotropism differ between plant species.
Journal of Experimental Botany, 2017Co-Authors: Yusuke Nakajima, Yoshitaka Nara, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Nobuharu Fujii, Hideyuki TakahashiAbstract:: The direction of auxin transport changes in gravistimulated roots, causing auxin accumulation in the lower side of horizontally reoriented roots. This study found that auxin was similarly involved in Hydrotropism and gravitropism in rice and pea roots, but Hydrotropism in Lotus japonicus roots was independent of both auxin transport and response. Application of either auxin transport inhibitors or an auxin response inhibitor decreased both Hydrotropism and gravitropism in rice roots, and reduced Hydrotropism in pea roots. However, Lotus roots treated with these inhibitors showed reduced gravitropism but an unaltered or an enhanced hydrotropic response. Inhibiting auxin biosynthesis substantially reduced both tropisms in rice and Lotus roots. Removing the final 0.2 mm (including the root cap) from the root tip inhibited gravitropism but not Hydrotropism in rice seedling roots. These results suggested that modes of auxin involvement in Hydrotropism differed between plant species. In rice roots, although auxin transport and responses were required for both gravitropism and Hydrotropism, the root cap was involved in the auxin regulation of gravitropism but not Hydrotropism. Hydrotropism in Lotus roots, however, may be regulated by a novel mechanism that is independent of both auxin transport and the TIR1/AFBs auxin response pathway.
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Root Hydrotropism is controlled via a cortex-specific growth mechanism
Nature Plants, 2017Co-Authors: Daniela Dietrich, Véronique Boudolf, Rahul Bhosale, Regina Antoni, Sotaro Hiratsuka, John A. Fozard, Akie Kobayashi, Tuan Nguyen, Lei Pang, Nobuharu FujiiAbstract:Plants can acclimate by using tropisms to link the direction of growth to environmental conditions. Hydrotropism allows roots to forage for water, a process known to depend on abscisic acid (ABA) but whose molecular and cellular basis remains unclear. Here we show that Hydrotropism still occurs in roots after laser ablation removed the meristem and root cap. Additionally, targeted expression studies reveal that Hydrotropism depends on the ABA signalling kinase SnRK2.2 and the Hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical cells. Conversely, Hydrotropism, but not gravitropism, is inhibited by preventing differential cell-length increases in the cortex, but not in other cell types. We conclude that root tropic responses to gravity and water are driven by distinct tissue-based mechanisms. In addition, unlike its role in root gravitropism, the elongation zone performs a dual function during a hydrotropic response, both sensing a water potential gradient and subsequently undergoing differential growth. Roots bend towards water. The root cortex in the elongation zone is the site of perception during Hydrotropism but also the site of differential root growth, which is different from gravitropism.
Gladys I. Cassab - One of the best experts on this subject based on the ideXlab platform.
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Root Hydrotropism and thigmotropism in Arabidopsis thaliana are differentially controlled by redox status.
Plant Signaling & Behavior, 2017Co-Authors: Georgina Ponce, Delfeena Eapen, Gabriel Corkidi, Fernando Lledias, Luis Cardenas, Gladys I. CassabAbstract:Factors that affect the direction of root growth in response to environmental signals influence crop productivity. We analyzed the root tropic responses of thioredoxin (trxs), thigmotropic (wav2-1), and hydrotropic (ahr1 and nhr1) Arabidopsis thaliana mutants treated with low concentrations of paraquat (PQ), which induces mild oxidative stress, and established a new method for evaluating root waviness (root bending effort, RBE). This method estimates root bending by measuring and summing local curvature over the whole length of the root, regardless of the asymmetry of the wavy pattern under thigmostimulation. In roots of the wav2-1 mutant, but not in those of the trxs and ahr1 mutants, RBE was significantly inhibited under mild oxidative stress. Thigmotropic stimulation of wav2-1 mutant roots, with or without PQ treatment, showed high levels of reactive oxygen species fluorescence, in contrast to roots of the ahr1 mutant. Furthermore, PQ inhibited root growth in all genotypes tested, except in the wav2-1 mutant. In a Hydrotropism assay of the trxs and wav2-1 mutants, root growth behavior was similar to the wild type with and without PQ, while the root growth of ahr1 and nhr1 mutants was diminished with PQ. These results indicate that hydrotropic and thigmotropic mutants respond differently to exogenous PQ, depending on the tropic stimulus perceived. Therefore, the mechanisms underlying Hydrotropism and thigmotropism may differ.
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root Hydrotropism and thigmotropism in arabidopsis thaliana are differentially controlled by redox status
Plant Signaling & Behavior, 2017Co-Authors: Georgina Ponce, Delfeena Eapen, Gabriel Corkidi, Fernando Lledias, Luis Cardenas, Gladys I. CassabAbstract:ABSTRACTFactors that affect the direction of root growth in response to environmental signals influence crop productivity. We analyzed the root tropic responses of thioredoxin (trxs), thigmotropic (wav2-1), and hydrotropic (ahr1 and nhr1) Arabidopsis thaliana mutants treated with low concentrations of paraquat (PQ), which induces mild oxidative stress, and established a new method for evaluating root waviness (root bending effort, RBE). This method estimates root bending by measuring and summing local curvature over the whole length of the root, regardless of the asymmetry of the wavy pattern under thigmostimulation. In roots of the wav2-1 mutant, but not in those of the trxs and ahr1 mutants, RBE was significantly inhibited under mild oxidative stress. Thigmotropic stimulation of wav2-1 mutant roots, with or without PQ treatment, showed high levels of reactive oxygen species fluorescence, in contrast to roots of the ahr1 mutant. Furthermore, PQ inhibited root growth in all genotypes tested, except in the...
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Synergy between root hydrotropic response and root biomass in maize (Zea mays L.) enhances drought avoidance
Plant Science, 2017Co-Authors: Delfeena Eapen, Jesús Martínez-guadarrama, Oralia Hernández-bruno, Leonardo Flores, Jorge Nieto-sotelo, Gladys I. CassabAbstract:Roots of higher plants change their growth direction in response to moisture, avoiding drought and gaining maximum advantage for development. This response is termed Hydrotropism. There have been few studies of root Hydrotropism in grasses, particularly in maize. Our goal was to test whether an enhanced hydrotropic response of maize roots correlates with a better adaptation to drought and partial/lateral irrigation in field studies. We developed a laboratory bioassay for testing hydrotropic response in primary roots of 47 maize elite DTMA (Drought Tolerant Maize for Africa) hybrids. After phenotyping these hybrids in the laboratory, selected lines were tested in the field. Three robust and three weak hybrids were evaluated employing three irrigation procedures: normal irrigation, partial lateral irrigation and drought. Hybrids with a robust hydrotropic response showed growth and developmental patterns, under drought and partial lateral irrigation, that differed from weak hydrotropic responders. A correlation between root crown biomass and grain yield in hybrids with robust hydrotropic response was detected. Hybrids with robust hydrotropic response showed earlier female flowering whereas several root system traits, such as projected root area, median width, maximum width, skeleton width, skeleton nodes, average tip diameter, rooting depth skeleton, thinner aboveground crown roots, as well as stem diameter, were considerably higher than in weak hydrotropic responders in the three irrigation procedures utilized. These results demonstrate the benefit of intensive phenotyping of Hydrotropism in primary roots since maize plants that display a robust hydrotropic response grew better under drought and partial lateral irrigation, indicating that a selection for robust Hydrotropism might be a promising breeding strategy to improve drought avoidance in maize.
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Robust root growth in altered hydrotropic response1 (ahr1) mutant of Arabidopsis is maintained by high rate of cell production at low water potential gradient.
Journal of Plant Physiology, 2017Co-Authors: Amed Salazar-blas, Delfeena Eapen, María Eugenia Campos, Laura Noriega-calixto, Tania Cruz-vázquez, Luis Castillo-olamendi, Gabriela Sepúlveda-jiménez, Helena Porta, Joseph G. Dubrovsky, Gladys I. CassabAbstract:Hydrotropism is the directional root growth response determined by water stimulus. In a water potential gradient system (WPGS) the roots of the Arabidopsis wild type have a diminished root growth compared to normal medium (NM). In contrast, the altered hydrotropic response1 (ahr1) mutant roots maintain their robust growth in the same WPGS. The aims of this work were to ascertain how ahr1 roots could sustain growth in the WPGS, with a special focus on the integration of cellular processes involved in the signaling that determines root growth during abiotic stress and their relation to Hydrotropism. Cellular analysis of the root apical meristem of ahr1 mutant contrary to the wild type showed an absence of changes in the meristem length, the elongation zone length, the length of fully elongated cells, and the cell cycle duration. The robust and steady root growth of ahr1 seedlings in the WPGS is explained by the mutant capacity to maintain cell production and cell elongation at the same level as in the NM. Analysis of auxin response at a transcriptional level showed that roots of the ahr1 mutant had a lower auxin response when grown in the WPGS, compared to wild type, indicating that auxin signaling participates in attenuation of root growth under water stress conditions. Also, wild type plants exhibited a high increase in proline content while ahr1 mutants showed minimum changes in the Normal Medium→Water Stress Medium (NM→WSM), a lower water potential gradient system than the WPGS. Accordingly, in this condition, gene expression of Δ1-6 Pyrroline-5-Carboxylate Synthetase1 (P5CS1) involved in proline synthesis strongly increased in wild type but not in ahr1 seedlings. The ahr1 phenotype shows unique features since the mutant root cells continue to proliferate and grow in the presence of a progressively negative water potential gradient at a level comparable to wild type growing in the NM. As such, it represents an exceptional resource for understanding Hydrotropism.
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Assays for Root Hydrotropism and Response to Water Stress
Plant Gravitropism, 2015Co-Authors: Delfeena Eapen, Jesús J. Martínez, Gladys I. CassabAbstract:Roots of most terrestrial plants show hydrotropic curvature when exposed to a moisture gradient. Though this root response is difficult to visualize in the soil habitat, there are reports of Hydrotropism as an inherent response of primary roots of different plant species, such as Arabidopsis thaliana, Pisum sativum, and Zea mays L., from in vitro system studies. Many plant species use Hydrotropism as a mechanism of avoidance to water stress. The actively growing root tip has the ability to change its direction towards greater water availability by differential growth in the elongation zone. The study of this tropic response has been challenged by the interaction of gravitropism, thigmotropism and possibly phototropism. It is hard to visualize hydrotropic curvature in vitro unless all other stimuli are neutralized by the presence of a moisture gradient. In this chapter, we describe methods for preparation of two assay systems used to visualize hydrotropic curvature in the primary roots of Arabidopsis and one moisture gradient system used for maize root seedlings.
Yutaka Miyazawa - One of the best experts on this subject based on the ideXlab platform.
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Correction to: Molecular mechanisms mediating root Hydrotropism: what we have observed since the rediscovery of Hydrotropism
Journal of Plant Research, 2020Co-Authors: Yutaka Miyazawa, Hideyuki TakahashiAbstract:The article Molecular mechanisms mediating root Hydrotropism
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Molecular mechanisms mediating root Hydrotropism: what we have observed since the rediscovery of Hydrotropism
Journal of Plant Research, 2020Co-Authors: Yutaka Miyazawa, Hideyuki TakahashiAbstract:Roots display directional growth toward moisture in response to a water potential gradient. Root Hydrotropism is thought to facilitate plant adaptation to continuously changing water availability. Hydrotropism has not been as extensively studied as gravitropism. However, comparisons of hydrotropic and gravitropic responses identified mechanisms that are unique to Hydrotropism. Regulatory mechanisms underlying the hydrotropic response appear to differ among different species. We recently performed molecular and genetic analyses of root Hydrotropism in Arabidopsis thaliana . In this review, we summarize the current knowledge of specific mechanisms mediating root Hydrotropism in several plant species.
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Root-tip-mediated inhibition of Hydrotropism is accompanied with the suppression of asymmetric expression of auxin-inducible genes in response to moisture gradients in cucumber roots.
PLOS ONE, 2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:In cucumber seedlings, gravitropism interferes with Hydrotropism, which results in the nearly complete inhibition of Hydrotropism under stationary conditions. However, hydrotropic responses are induced when the gravitropic response in the root is nullified by clinorotation. Columella cells in the root cap sense gravity, which induces the gravitropic response. In this study, we found that removing the root tip induced Hydrotropism in cucumber roots under stationary conditions. The application of auxin transport inhibitors to cucumber seedlings under stationary conditions suppressed the hydrotropic response induced by the removal of the root tip. To investigate the expression of genes related to Hydrotropism in de-tipped cucumber roots, we conducted transcriptome analysis of gene expression by RNA-Seq using seedlings exhibiting hydrotropic and gravitropic responses. Of the 21 and 45 genes asymmetrically expressed during hydrotropic and gravitropic responses, respectively, five genes were identical. Gene ontology (GO) analysis indicated that the category auxin-inducible genes was significantly enriched among genes that were more highly expressed in the concave side of the root than the convex side during hydrotropic or gravitropic responses. Reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR) analysis revealed that root Hydrotropism induced under stationary conditions (by removing the root tip) was accompanied by the asymmetric expression of several auxin-inducible genes. However, intact roots did not exhibit the asymmetric expression patterns of auxin-inducible genes under stationary conditions, even in the presence of a moisture gradient. These results suggest that the root tip inhibits Hydrotropism by suppressing the induction of asymmetric auxin distribution. Auxin transport and distribution not mediated by the root tip might play a role in Hydrotropism in cucumber roots.
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Effects of root tip removal on root Hydrotropism in cucumber seedlings.
2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:(A–B) Effects of root tip removal on root gravitropism in cucumber seedlings. 24-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were placed in a vertical or horizontal position. After 1 h, root curvature (A) and length (B) were measured. Experiments (using eight seedlings) were repeated three times, and the mean ± SE was calculated. (C–E) Effects of root tip removal on root Hydrotropism in cucumber seedlings. 18-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were exposed to a moisture gradient induced by K2CO3. After incubation under stationary conditions for 4 h and 9 h or in a 3D clinostat for 9 h, root curvature (C) and length (D) were measured. Experiments (using seven seedlings) were repeated three times, and the mean ± SE was calculated. Different letters indicate statistically significant differences (P
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gravitropism interferes with Hydrotropism via counteracting auxin dynamics in cucumber roots clinorotation and spaceflight experiments
New Phytologist, 2017Co-Authors: Keita Morohashi, Miki Okamoto, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Yutaka Miyazawa, Nobuharu Fujii, Toru ShimazuAbstract:Summary Roots of land plants show gravitropism and Hydrotropism in response to gravity and moisture gradients, respectively, for controlling their growth orientation. Gravitropism interferes with Hydrotropism, although the mechanistic aspects are poorly understood. Here, we differentiated Hydrotropism from gravitropism in cucumber roots by conducting clinorotation and spaceflight experiments. We also compared mechanisms regulating Hydrotropism and auxin-regulated gravitropism. Clinorotated or microgravity (μG)-grown cucumber seedling roots hydrotropically bent toward wet substrate in the presence of moisture gradients, but they grew straight in the direction of normal gravitational force at the Earth's surface (1G) on the ground or centrifuge-generated 1G in space. The roots appeared to become hydrotropically more sensitive to moisture gradients under μG conditions in space. Auxin transport inhibitors significantly reduced the hydrotropic response of clinorotated seedling roots. The auxin efflux protein CsPIN5 was differentially expressed in roots of both clinorotated and μG-grown seedlings; with higher expression in the high-humidity (concave) side than the low-humidity (convex) side of hydrotropically responding roots. Our results suggest that roots become hydrotropically sensitive in μG, and CsPIN5-mediated auxin transport has an important role in inducing root Hydrotropism. Thus, hydrotropic and gravitropic responses in cucumber roots may compete via differential auxin dynamics established in response to moisture gradients and gravity.
Akie Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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Plasma Membrane-Associated Ca2+-Binding Protein PCaP1 is Involved in Root Hydrotropism of Arabidopsis thaliana
Plant and Cell Physiology, 2019Co-Authors: Natsuki Tanaka-takada, Akie Kobayashi, Hideyuki Takahashi, Takehiro Kamiya, Toshinori Kinoshita, Masayoshi MaeshimaAbstract:Root Hydrotropism is an essential growth response to water potential gradients in plants. To understand the mechanism, fundamental elements such as MIZU-KUSSEI 1 (MIZ1) have been investigated extensively. We investigated the physiological role of a plasma membrane-associated cation-binding protein (PCaP1) and examined the effect of PCaP1 loss-of-function mutations on root Hydrotropism. pcap1 knockout mutants showed a defect in root bending as a hydrotropic response, although gravitropism was normal in pcap1 mutants. When pcap1 seedlings were treated with abscisic acid, a negative regulator of gravitropism, the seedlings showed normal gravitropism. The Hydrotropism defect in pcap1 mutants was clearly rescued by introducing the genomic sequence of PCaP1 with an endodermis-specific promoter. Analysis of PCaP1-greenfluorescent protein-expressing roots by confocal laser scanning microscopy revealed that PCaP1 was stably associated with the plasma membrane in most cells, but in the cytoplasm of endodermal cells at the bending region. Furthermore, we prepared a transgenic line overexpressing MIZ1 on the pcap1 background and found that the pcap1 Hydrotropism defect was rescued. Our results indicate that PCaP1 in the endodermal cells of the root elongation zone is involved in the hydrotropic response. We suggest that PCaP1 contributes to Hydrotropism through a MIZ1-independent pathway or as one of the upstream components that transduce water potential signals to MIZ1.
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Root-tip-mediated inhibition of Hydrotropism is accompanied with the suppression of asymmetric expression of auxin-inducible genes in response to moisture gradients in cucumber roots.
PLOS ONE, 2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:In cucumber seedlings, gravitropism interferes with Hydrotropism, which results in the nearly complete inhibition of Hydrotropism under stationary conditions. However, hydrotropic responses are induced when the gravitropic response in the root is nullified by clinorotation. Columella cells in the root cap sense gravity, which induces the gravitropic response. In this study, we found that removing the root tip induced Hydrotropism in cucumber roots under stationary conditions. The application of auxin transport inhibitors to cucumber seedlings under stationary conditions suppressed the hydrotropic response induced by the removal of the root tip. To investigate the expression of genes related to Hydrotropism in de-tipped cucumber roots, we conducted transcriptome analysis of gene expression by RNA-Seq using seedlings exhibiting hydrotropic and gravitropic responses. Of the 21 and 45 genes asymmetrically expressed during hydrotropic and gravitropic responses, respectively, five genes were identical. Gene ontology (GO) analysis indicated that the category auxin-inducible genes was significantly enriched among genes that were more highly expressed in the concave side of the root than the convex side during hydrotropic or gravitropic responses. Reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR) analysis revealed that root Hydrotropism induced under stationary conditions (by removing the root tip) was accompanied by the asymmetric expression of several auxin-inducible genes. However, intact roots did not exhibit the asymmetric expression patterns of auxin-inducible genes under stationary conditions, even in the presence of a moisture gradient. These results suggest that the root tip inhibits Hydrotropism by suppressing the induction of asymmetric auxin distribution. Auxin transport and distribution not mediated by the root tip might play a role in Hydrotropism in cucumber roots.
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Effects of root tip removal on root Hydrotropism in cucumber seedlings.
2018Co-Authors: Nobuharu Fujii, Chiaki Yamazaki, Motoshi Kamada, Haruo Kasahara, Ikuko Osada, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Sachiko Miyabayashi, Toru ShimazuAbstract:(A–B) Effects of root tip removal on root gravitropism in cucumber seedlings. 24-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were placed in a vertical or horizontal position. After 1 h, root curvature (A) and length (B) were measured. Experiments (using eight seedlings) were repeated three times, and the mean ± SE was calculated. (C–E) Effects of root tip removal on root Hydrotropism in cucumber seedlings. 18-h-old cucumber seedlings in which the root tip was either not removed (Intact) or removed (De-tipped) were exposed to a moisture gradient induced by K2CO3. After incubation under stationary conditions for 4 h and 9 h or in a 3D clinostat for 9 h, root curvature (C) and length (D) were measured. Experiments (using seven seedlings) were repeated three times, and the mean ± SE was calculated. Different letters indicate statistically significant differences (P
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Auxin transport and response requirements for root Hydrotropism differ between plant species.
Journal of Experimental Botany, 2017Co-Authors: Yusuke Nakajima, Yoshitaka Nara, Akie Kobayashi, Tomoki Sugita, Yutaka Miyazawa, Nobuharu Fujii, Hideyuki TakahashiAbstract:: The direction of auxin transport changes in gravistimulated roots, causing auxin accumulation in the lower side of horizontally reoriented roots. This study found that auxin was similarly involved in Hydrotropism and gravitropism in rice and pea roots, but Hydrotropism in Lotus japonicus roots was independent of both auxin transport and response. Application of either auxin transport inhibitors or an auxin response inhibitor decreased both Hydrotropism and gravitropism in rice roots, and reduced Hydrotropism in pea roots. However, Lotus roots treated with these inhibitors showed reduced gravitropism but an unaltered or an enhanced hydrotropic response. Inhibiting auxin biosynthesis substantially reduced both tropisms in rice and Lotus roots. Removing the final 0.2 mm (including the root cap) from the root tip inhibited gravitropism but not Hydrotropism in rice seedling roots. These results suggested that modes of auxin involvement in Hydrotropism differed between plant species. In rice roots, although auxin transport and responses were required for both gravitropism and Hydrotropism, the root cap was involved in the auxin regulation of gravitropism but not Hydrotropism. Hydrotropism in Lotus roots, however, may be regulated by a novel mechanism that is independent of both auxin transport and the TIR1/AFBs auxin response pathway.
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root Hydrotropism is controlled via a cortex specific growth mechanism
Nature plants, 2017Co-Authors: Daniela Dietrich, Véronique Boudolf, Rahul Bhosale, Regina Antoni, John A. Fozard, Akie Kobayashi, Tuan Nguyen, Lei Pang, Sotaro HiratsukaAbstract:Plants can acclimate by using tropisms to link the direction of growth to environmental conditions. Hydrotropism allows roots to forage for water, a process known to depend on abscisic acid (ABA) but whose molecular and cellular basis remains unclear. Here, we show that Hydrotropism still occurs in roots after laser ablation removed the meristem and root cap. Additionally, targeted expression studies reveal that Hydrotropism depends on the ABA signalling kinase, SnRK2.2, and the Hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical cells. Conversely, Hydrotropism, but not gravitropism, is inhibited by preventing differential cell-length increases in the cortex, but not in other cell types. We conclude that root tropic responses to gravity and water are driven by distinct tissue-based mechanisms. In addition, unlike its role in root gravitropism, the elongation zone performs a dual function during a hydrotropic response, both sensing a water potential gradient and subsequently undergoing differential growth.
