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Gloria K Muday - One of the best experts on this subject based on the ideXlab platform.
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transport of the two natural Auxins indole 3 butyric acid and indole 3 acetic acid in arabidopsis
Plant Physiology, 2003Co-Authors: Aaron M Rashotte, Julie Poupart, Candace S Waddell, Gloria K MudayAbstract:Polar transport of the natural Auxin indole-3-acetic acid (IAA) is important in a number of plant developmental processes. However, few studies have investigated the polar transport of other endogenous Auxins, such as indole-3-butyric acid (IBA), in Arabidopsis. This study details the similarities and differences between IBA and IAA transport in several tissues of Arabidopsis. In the inflorescence axis, no significant IBA movement was detected, whereas IAA is transported in a basipetal direction from the meristem tip. In young seedlings, both IBA and IAA were transported only in a basipetal direction in the hypocotyl. In roots, both Auxins moved in two distinct polarities and in specific tissues. The kinetics of IBA and IAA transport appear similar, with transport rates of 8 to 10 mm per hour. In addition, IBA transport, like IAA transport, is saturable at high concentrations of Auxin, suggesting that IBA transport is protein mediated. Interestingly, IAA efflux inhibitors and mutations in genes encoding putative IAA transport proteins reduce IAA transport but do not alter IBA movement, suggesting that different Auxin transport protein complexes are likely to mediate IBA and IAA transport. Finally, the physiological effects of IBA and IAA on hypocotyl elongation under several light conditions were examined and analyzed in the context of the differences in IBA and IAA transport. Together, these results present a detailed picture of IBA transport and provide the basis for a better understanding of the transport of these two endogenous Auxins.
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tomato root growth gravitropism and lateral development correlation with Auxin transport
Plant Physiology and Biochemistry, 1994Co-Authors: Gloria K Muday, P HaworthAbstract:Abstract Tomato (Lycopersicon esculentum, Mill.) roots were analyzed during growth on agar plates. Growth of these roots was inhibited by the Auxin transport inhibitors naphthylphthalamic acid (NPA) and semicarbazone derivative I (SCB-1). The effect of Auxin transport inhibitors on root gravitropism was analyzed by measurement of the angle of gravitropic curvature after the roots were reoriented 90 degrees from the vertical. NPA and SCB-1 abolished both the response of these roots to gravity and the formation of lateral roots, with SCB-1 being the more effective at inhibition. Auxins also inhibited root growth. Both Auxins tested has a slight effect on the gravity response, but this effect is probably indirect, since Auxins reduced the growth rate. Auxins also stimulated lateral root growth at concentration where primary root growth was inhibited. When roots were treated with both IAA and NPA simultaneously, a cumulative inhibition of root growth was found. When both compounds were applied together, analysis of gravitropism and lateral root formation indicated that the dominant effect was exerted by Auxin transport inhibitors. Together, these data suggest a model for the role of Auxin transport in controlling both primary and lateral root growth.
Katharina Pawlowski - One of the best experts on this subject based on the ideXlab platform.
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accumulation of and response to Auxins in roots and nodules of the actinorhizal plant datisca glomerata compared to the model legume medicago truncatula
Frontiers in Plant Science, 2019Co-Authors: Irina V Demina, Pooja Jha Maity, Anurupa Nagchowdhury, Eric Van Der Graaff, Kirill N Demchenko, Thomas Roitsch, Ulrike Mathesius, Katharina PawlowskiAbstract:Actinorhizal nodules are structurally different from legume nodules and show a greater similarity to lateral roots. Because of the important role of Auxins in lateral root and nodule formation, Auxin profiles were examined in roots and nodules of the actinorhizal species Datisca glomerata and the model legume Medicago truncatula. The Auxin response in roots and nodules of both species was analyzed in transgenic root systems expressing a beta-glucuronidase gene under control of the synthetic Auxin-responsive promoter DR5. The effects of two different Auxin on root development were compared for both species. The Auxin present in nodules at the highest levels was phenylacetic acid (PAA). No differences were found between the concentrations of active Auxins of roots vs. nodules, while levels of the Auxin conjugate indole-3-acetic acid-alanine were increased in nodules compared to roots of both species. Because Auxins typically act in concert with cytokinins, cytokinins were also quantified. Concentrations of cis-zeatin and some glycosylated cytokinins were dramatically increased in nodules compared to roots of D. glomerata, but not of M. truncatula. The ratio of active Auxins to cytokinins remained similar in nodules compared to roots in both species. The Auxin response, as shown by the activation of the DR5 promoter, seemed significantly reduced in nodules compared to roots of both species, suggesting the accumulation of Auxins in cell types that do not express the signal transduction pathway leading to DR5 activation. Effects on root development were analyzed for the synthetic Auxin naphthaleneacetic acid (NAA) and PAA, the dominant Auxin in nodules. Both Auxins had similar effects, except that the sensitivity of roots to PAA was lower than to NAA. However, while the effects of both Auxins on primary root growth were similar for both species, effects on root branching were different: both Auxins had the classical positive effect on root branching in M. truncatula, but a negative effect in D. glomerata. Such a negative effect of exogenous Auxin on root branching has previously been found for a cucurbit that forms lateral root primordia in the meristem of the parental root; however, root branching in D. glomerata does not follow that pattern.
Irina V Demina - One of the best experts on this subject based on the ideXlab platform.
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accumulation of and response to Auxins in roots and nodules of the actinorhizal plant datisca glomerata compared to the model legume medicago truncatula
Frontiers in Plant Science, 2019Co-Authors: Irina V Demina, Pooja Jha Maity, Anurupa Nagchowdhury, Eric Van Der Graaff, Kirill N Demchenko, Thomas Roitsch, Ulrike Mathesius, Katharina PawlowskiAbstract:Actinorhizal nodules are structurally different from legume nodules and show a greater similarity to lateral roots. Because of the important role of Auxins in lateral root and nodule formation, Auxin profiles were examined in roots and nodules of the actinorhizal species Datisca glomerata and the model legume Medicago truncatula. The Auxin response in roots and nodules of both species was analyzed in transgenic root systems expressing a beta-glucuronidase gene under control of the synthetic Auxin-responsive promoter DR5. The effects of two different Auxin on root development were compared for both species. The Auxin present in nodules at the highest levels was phenylacetic acid (PAA). No differences were found between the concentrations of active Auxins of roots vs. nodules, while levels of the Auxin conjugate indole-3-acetic acid-alanine were increased in nodules compared to roots of both species. Because Auxins typically act in concert with cytokinins, cytokinins were also quantified. Concentrations of cis-zeatin and some glycosylated cytokinins were dramatically increased in nodules compared to roots of D. glomerata, but not of M. truncatula. The ratio of active Auxins to cytokinins remained similar in nodules compared to roots in both species. The Auxin response, as shown by the activation of the DR5 promoter, seemed significantly reduced in nodules compared to roots of both species, suggesting the accumulation of Auxins in cell types that do not express the signal transduction pathway leading to DR5 activation. Effects on root development were analyzed for the synthetic Auxin naphthaleneacetic acid (NAA) and PAA, the dominant Auxin in nodules. Both Auxins had similar effects, except that the sensitivity of roots to PAA was lower than to NAA. However, while the effects of both Auxins on primary root growth were similar for both species, effects on root branching were different: both Auxins had the classical positive effect on root branching in M. truncatula, but a negative effect in D. glomerata. Such a negative effect of exogenous Auxin on root branching has previously been found for a cucurbit that forms lateral root primordia in the meristem of the parental root; however, root branching in D. glomerata does not follow that pattern.
Hiroshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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development of 4 methoxy 7 nitroindolinyl mni caged Auxins which are extremely stable in planta
Bioorganic & Medicinal Chemistry Letters, 2015Co-Authors: Naoyuki Kusaka, Soma Yamasaki, Yunde Zhao, Hiroshi NozakiAbstract:Phytohormone Auxin is a master regulator in plant growth and development. Regulation of cellular Auxin level plays a central role in plant development. Auxin polar transport system modulates an Auxin gradient that determines plant developmental process in response to environmental conditions and developmental programs. Photolabile caged Auxins allow optical control of artificial Auxin gradients at cellular resolution. Especially, two-photon uncaging system achieves high spatiotemporal control of photolysis reaction at two-photon cross-section. However, the development of caged versions of Auxin has been limited by the instability of the caged Auxins to higher plant metabolic activities. Here, we describe the synthesis and application of highly stable caged Auxins, 4-methoxy-7-nitroindolinyl (MNI)-caged Auxins. Natural Auxin, indole 3-acetic acid, and two synthetic Auxins, 1-NAA and 2,4-D were caged by MNI caging group. MNI-caged Auxins showed a high stability in planta and a rapid release the original Auxin when photolyzed. We demonstrated that optical control of Auxin-responsive gene expression and Auxin-related physiological responses by using MNI-caged Auxins. We anticipate that MNI-caged Auxins will be an effective tool for high-resolution control of endogenous Auxin level.
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Toyocamycin specifically inhibits Auxin signaling mediated by SCFTIR1 pathway
Phytochemistry, 2009Co-Authors: Shuichi Kamio, Yutaka Oono, Leroy B. Townsend, Hiroshi NozakiAbstract:Abstract The Auxins, plant hormones, play a crucial role in many aspects of plant development by regulating cell division, elongation and differentiation. Toyocamycin, a nucleoside-type antibiotic, was identified as Auxin signaling inhibitor in a screen of microbial extracts for inhibition of the Auxin-inducible reporter gene assay. Toyocamycin specifically inhibited Auxin-responsive gene expression, but did not affect other hormone-inducible gene expression. Toyocamycin also blocked Auxin-enhanced degradation of the Aux/IAA repressor modulated by the SCF(TIR1) ubiquitin–proteasome pathway without inhibiting proteolytic activity of proteasome. Furthermore, toyocamycin inhibited Auxin-induced lateral root formation and epinastic growth of cotyledon in the Arabidopsis thaliana plant. This evidence suggested that toyocamycin would act on the ubiquitination process regulated by SCF(TIR1) machineries. To address the structural requirements for the specific activity of toyocamycin on Auxin signaling, the structure-activity relationships of nine toyocamycin-related compounds, including sangivamycin and tubercidin, were investigated.
Richard M Napier - One of the best experts on this subject based on the ideXlab platform.
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defining binding efficiency and specificity of Auxins for scftir1 afb aux iaa co receptor complex formation
ACS Chemical Biology, 2014Co-Authors: Sarah Lee, Stefan Kepinski, Shanthy Sundaram, Lynne Armitage, John Paul Evans, Tim Hawkes, Noel Ferro, Richard M NapierAbstract:Structure-activity profiles for the phytohormone Auxin have been collected for over 70 years, and a number of synthetic Auxins are used in agriculture. Auxin classification schemes and binding models followed from understanding Auxin structures. However, all of the data came from whole plant bioassays, meaning the output was the integral of many different processes. The discovery of Transport Inhibitor-Response 1 (TIR1) and the Auxin F-Box (AFB) proteins as sites of Auxin perception and the role of Auxin as molecular glue in the assembly of co-receptor complexes has allowed the development of a definitive quantitative structure-activity relationship for TIR1 and AFB5. Factorial analysis of binding activities offered two uncorrelated factors associated with binding efficiency and binding selectivity. The six maximum-likelihood estimators of Efficiency are changes in the overlap matrixes, inferring that Efficiency is related to the volume of the electronic system. Using the subset of compounds that bound strongly, chemometric analyses based on quantum chemical calculations and similarity and self-similarity indices yielded three classes of Specificity that relate to differential binding. Specificity may not be defined by any one specific atom or position and is influenced by coulomb matrixes, suggesting that it is driven by electrostatic forces. These analyses give the first receptor-specific classification of Auxins and indicate that AFB5 is the preferred site for a number of Auxinic herbicides by allowing interactions with analogues having van der Waals surfaces larger than that of indole-3-acetic acid. The quality factors are also examined in terms of long-standing models for the mechanism of Auxin binding.
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defining binding efficiency and specificity of Auxins for scf tir1 afb aux iaa co receptor complex formation
ACS Chemical Biology, 2014Co-Authors: Sarah Lee, Stefan Kepinski, Shanthy Sundaram, Lynne Armitage, John Paul Evans, Noel Ferro, Tim R Hawkes, Richard M NapierAbstract:Structure-activity profiles for the phytohormone Auxin have been collected for over 70 years, and a number of synthetic Auxins are used in agriculture. Auxin classification schemes and binding models followed from understanding Auxin structures. However, all of the data came from whole plant bioassays, meaning the output was the integral of many different processes. The discovery of Transport Inhibitor-Response 1 (TIR1) and the Auxin F-Box (AFB) proteins as sites of Auxin perception and the role of Auxin as molecular glue in the assembly of co-receptor complexes has allowed the development of a definitive quantitative structure-activity relationship for TIR1 and AFB5. Factorial analysis of binding activities offered two uncorrelated factors associated with binding efficiency and binding selectivity. The six maximum-likelihood estimators of Efficiency are changes in the overlap matrixes, inferring that Efficiency is related to the volume of the electronic system. Using the subset of compounds that bound strongly, chemometric analyses based on quantum chemical calculations and similarity and self-similarity indices yielded three classes of Specificity that relate to differential binding. Specificity may not be defined by any one specific atom or position and is influenced by coulomb matrixes, suggesting that it is driven by electrostatic forces. These analyses give the first receptor-specific classification of Auxins and indicate that AFB5 is the preferred site for a number of Auxinic herbicides by allowing interactions with analogues having van der Waals surfaces larger than that of indole-3-acetic acid. The quality factors are also examined in terms of long-standing models for the mechanism of Auxin binding.
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Patch-clamp analysis establishes a role for an Auxin binding protein in the Auxin stimulation of plasma membrane current in Zea mays protoplasts
The Plant Journal, 1993Co-Authors: Annegret Ruck, Klaus Palme, Richard M Napier, Michael A. Venis, Hubert H. FelleAbstract:The electrical response of Zea mays protoplasts to different Auxins and to antibodies raised against an ER-located Auxin binding protein from maize (Zm-ERabp1), was investigated using the patch-clamp technique (whole-cell configuration). Following a lag-phase of 30–40 seconds, indole-3-acetic acid and 1-naphthylacetic acid induced an outwardly directed current of positive charge in a concentration-dependent manner. This current was further increased by the fungal toxin fusicoccin (FC). The current was observed only in the presence of Mg2+-ATP in the patch-pipette and was abolished after addition of erythrosin B, an inhibitor of H+-ATPase, to the protoplasts indicating that the plasma membrane H+-ATPase is activated by Auxins and fusicoccin. Addition of antibodies directed against Zm-ERabp1 abolished the current induced by Auxins, without affecting the response of protoplasts to fusicoccin. Antibodies directed against a peptide representing part of the putative Auxin binding domain of Zm-ERabp1 showed Auxin agonist activity, stimulating an outwardly directed membrane current in the absence of Auxin. These results suggest that (i) Zm-ERabp1 or antigenically related proteins represent a site for Auxin perception through which the plasma membrane H+-ATPase is activated, and (ii) that the activation of the H+-ATPase by such proteins is initiated from outside the plasma membrane.