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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.
Ken-ichiro Hayashi - One of the best experts on this subject based on the ideXlab platform.
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The Tetrazole Analogue of the Auxin Indole-3-acetic Acid Binds Preferentially to TIR1 and Not AFB5.
ACS Chemical Biology, 2018Co-Authors: Mussa Quareshy, Justyna Prusinska, Martin Kieffer, Kosuke Fukui, Alonso J. Pardal, Silke Lehmann, Patrick Schäfer, Charo I. Del Genio, Stefan Kepinski, Ken-ichiro HayashiAbstract:Indole-3-acetic acid (auxin) is considered one of the cardinal hormones in plant growth and development. It regulates a wide range of processes throughout the plant. Synthetic Auxins exploit the auxin-signaling pathway and are valuable as herbicidal agrochemicals. Currently, despite a diversity of chemical scaffolds all synthetic Auxins have a carboxylic acid as the active core group. By applying bio-isosteric replacement we discovered that indole-3-tetrazole was active by surface plasmon resonance spectrometry, showing that the tetrazole could initiate assembly of the Transport Inhibitor Resistant 1 (TIR1) auxin coreceptor complex. We then tested the tetrazole’s efficacy in a range of whole plant physiological assays and in protoplast reporter assays, which all confirmed auxin activity, albeit rather weak. We then tested indole-3-tetrazole against the AFB5 homologue of TIR1, finding that binding was selective against TIR1, absent with AFB5. The kinetics of binding to TIR1 are contrasted to those for the ...
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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: Ken-ichiro Hayashi, 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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Manipulation of Intracellular Auxin in a Single Cell by Light with Esterase-Resistant Caged Auxins
Chembiochem : a European journal of chemical biology, 2009Co-Authors: Naoyuki Kusaka, Ken-ichiro Hayashi, Jan Maisch, Peter Nick, Hiroshi NozakiAbstract:Auxin, a plant hormone, is polar transported from its site of production. This auxin polar transport system establishes an auxin gradient in plant tissue that is necessary for proper plant development. Therefore, the spatial effect of the auxin gradient on plant development is highly important for the understanding of plant auxin responses. Herein we report the design, syntheses and biological properties of esterase-resistant caged Auxins. The conventional caging group, 2-nitrobenzyl ester, was found to be enzymatically hydrolyzed in plant cells and released original auxin without photolysis. The esterase-resistant caging group, (2,5-dimethoxyphenyl)(2-nitrobenzyl) ester, (DMPNB) was designed to improve the stability of caged Auxins. Three Auxins, indole 3-acetic acid, naphthalene 1-acetic acid and 2,4-dichlorophenoxy acetic acid were caged with the DMPNB caging group. DMPNB-caged Auxins were inactive within a plant cell until photolysis, but they release Auxins with photoirradiation to activate auxin-responsive gene expression. We demonstrated spatial and temporal control of intracellular auxin levels with photoirradiation by using this caged auxin system and were able to photocontrol the physiological auxin response in Arabidopsis plants. Additionally, the photoirradiation of DMPNB-caged auxin within a single cell can manipulate the intracellular auxin level and triggers auxin response.
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Toyocamycin specifically inhibits auxin signaling mediated by SCFTIR1 pathway
Phytochemistry, 2009Co-Authors: Ken-ichiro Hayashi, 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.
P Haworth - One of the best experts on this subject based on the ideXlab platform.
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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.
Todd J Cooke - One of the best experts on this subject based on the ideXlab platform.
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the effects of exogenous Auxins on endogenous indole 3 acetic acid metabolism the implications for carrot somatic embryogenesis
Plant Physiology, 1996Co-Authors: David M Ribnicky, Jerry D. Cohen, Nebojsa Ilic, Todd J CookeAbstract:The effect of auxin application on auxin metabolism was investigated in excised hypocotyl cultures of carrot (Daucus carota). Concentrations of both free and conjugated indole-3-acetic acid (IAA), [2H4]IAA, 2,4-dichlorophenoxyacetic acid, and naphthaleneacetic acid (NAA) were measured by mass spectroscopy using stable-isotope-labeled internal standards. [13C1]NAA was synthesized for this purpose, thus extending the range of Auxins that can be assayed by stable-isotope techniques. 2,4-Dichlorophenoxyacetic acid promoted callus proliferation of the excised hypocotyls, accumulated as the free form in large quantities, and had minor effects on endogenous IAA concentrations. NAA promoted callus proliferation and the resulting callus became organogenic, producing both roots and shoots. NAA was found mostly in the conjugated form and had minor effects on endogenous IAA concentrations. [2H4]IAA had no visible effect on the growth pattern of cultured hypocotyls, possibly because it was rapidly metabolized to form inactive conjugates or possibly because it mediated a decrease in endogenous IAA concentrations by an apparent feedback mechanism. The presence of exogenous Auxins did not affect tryptophan labeling of either the endogenous tryptophan or IAA pools. This suggested that exogenous Auxins did not alter the IAA biosynthetic pathway, but that synthetic Auxins did appear to be necessary to induce callus proliferation, which was essential for excised hypocotyls to gain the competence to form somatic embryos.
Laura De La Canal - One of the best experts on this subject based on the ideXlab platform.
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sunflower root growth regulation the role of jasmonic acid and its relation with Auxins
Plant Growth Regulation, 2012Co-Authors: Georgina De La Paz Corti Monzon, Marcela Pinedo, Lorenzo Lamattina, Laura De La CanalAbstract:Jasmonates are lipid-derived hormones that act as signal molecules in abiotic and biotic stresses and influence several aspects of plant growth and development. In this work we have investigated the effect of jasmonic acid (JA) on the root architecture of Helianthus annuus seedlings and if JA and Auxins interact to modulate the growth of the primary root (PR) and lateral roots (LR). The addition of μM concentrations of JA to the growing medium of sunflower seedlings decreased the growth of the PR and LR, and also reduced the number of LR. Moreover, treatment with ibuprofen, an inhibitor of JA synthesis, increased PR and LR root length causing a deep effect on root architecture. Hence, not only exogenous but also the endogenous JA regulates sunflower root growth. Microscopic analysis showed that the application of JA reduces the cortex cell length and the estimated cell production rate in root meristem while ibuprofen only affects the cell elongation. A possible interaction between JA and Auxins to regulate root growth was further analyzed. We show that JA produced its phenotype even in the presence of reduced levels of auxin generated by treatment with an auxin transport inhibitor. Besides, the auxin produced its phenotype even when ibuprofen was applied. In conclusion, JA may induce primary and lateral root growth inhibition in sunflower by an auxin-independent pathway.