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Tang Q, Tillmann M, Cohen JD. Analytical methods for stable isotope labeling to elucidate rapid auxin kinetics in Arabidopsis thaliana. PLoS One 2024; 19:e0303992. [PMID: 38776314 PMCID: PMC11111016 DOI: 10.1371/journal.pone.0303992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 05/04/2024] [Indexed: 05/24/2024] Open
Abstract
The phytohormone auxin plays a critical role in plant growth and development. Despite significant progress in elucidating metabolic pathways of the primary bioactive auxin, indole-3-acetic acid (IAA), over the past few decades, key components such as intermediates and enzymes have not been fully characterized, and the dynamic regulation of IAA metabolism in response to environmental signals has not been completely revealed. In this study, we established a protocol employing a highly sensitive liquid chromatography-mass spectrometry (LC-MS) instrumentation and a rapid stable isotope labeling approach. We treated Arabidopsis seedlings with two stable isotope labeled precursors ([13C6]anthranilate and [13C8, 15N1]indole) and monitored the label incorporation into proposed indolic compounds involved in IAA biosynthetic pathways. This Stable Isotope Labeled Kinetics (SILK) method allowed us to trace the turnover rates of IAA pathway precursors and product concurrently with a time scale of seconds to minutes. By measuring the entire pathways over time and using different isotopic tracer techniques, we demonstrated that these methods offer more detailed information about this complex interacting network of IAA biosynthesis, and should prove to be useful for studying auxin metabolic network in vivo in a variety of plant tissues and under different environmental conditions.
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Affiliation(s)
- Qian Tang
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Molly Tillmann
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Jerry D. Cohen
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota, United States of America
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Kebert M, Kostić S, Vuksanović V, Gavranović Markić A, Kiprovski B, Zorić M, Orlović S. Metal- and Organ-Specific Response to Heavy Metal-Induced Stress Mediated by Antioxidant Enzymes' Activities, Polyamines, and Plant Hormones Levels in Populus deltoides. PLANTS (BASEL, SWITZERLAND) 2022; 11:3246. [PMID: 36501286 PMCID: PMC9741192 DOI: 10.3390/plants11233246] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 11/20/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Besides anthropogenic factors, climate change causes altered precipitation patterns that indirectly affect the increase of heavy metals in soils due to hydrological effects and enhanced leaching (i.e., Cd and Ni), especially in the vicinity of mines and smelters. Phytoextraction is a well-known, powerful "green" technique for environmental clean-up that uses plants to extract, sequester, and/or detoxify heavy metals, and it makes significant contributions to the removal of persistent inorganic pollutants from soils. Poplar species, due to their growth features, high transpiration rate, large biomass, and feasible reproduction represent great candidates for phytoextraction technology. However, the consequences of concomitant oxidative stress upon plant metabolism and the mechanism of the poplar's tolerance to heavy metal-induced stress are still not completely understood. In this study, cuttings of poplar species (Populus deltoides W. Bartram ex Marshall) were separately exposed to two heavy metals (Cd2+ and Ni2+) that were triple the maximum allowed amount (MAA) (according to national legislation). The aim of the study was to estimate the effects of heavy metals on: (I) the accumulation of free and conjugated polyamines, (II) plant hormones (including abscisic acid-ABA and indole-3-acetic acid-IAA), and (III) the activities of different antioxidant enzymes at root and leaf levels. By using the selected ion monitoring (SIM) mode of gas chromatography with mass spectrometry (GC/MS) coupled with the isotopically labeled technique, amounts of ABA and IAA were quantified, while polyamine amounts were determined by using high-performance liquid chromatography (HPLC) with fluorometric detection after derivatization. The results showed that P. deltoides responded to elevated concentrations of heavy metals in soils by exhibiting metal- and organ-specific tolerance. Knowledge about tolerance mechanisms is of great importance for the development of phytoremediation technology and afforestation programs for polluted soils.
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Affiliation(s)
- Marko Kebert
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia
| | - Saša Kostić
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia
| | - Vanja Vuksanović
- Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovića 8, 21000 Novi Sad, Serbia
| | - Anđelina Gavranović Markić
- Division for Genetics, Forest Tree Breeding and Seed Science, Croatian Forest Research Institute, Cvjetno Naselje 41, HR-10450 Jastrebarsko, Croatia
| | - Biljana Kiprovski
- Institute of Field and Vegetable Crops, National Institute of the Republic of Serbia, Maksima Gorkog 30, 21000 Novi Sad, Serbia
| | - Martina Zorić
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia
| | - Saša Orlović
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia
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Ismail AM, Butler IS, Abou El Maaty WM, Mostafa SI. Anticancer and DNA Interaction of New Zinc(II), Palladium(II), Platinum(II) and Silver(I) Complexes Based on Indol-3-Acetic Acid; Solid and Solution Studies. Polycycl Aromat Compd 2022. [DOI: 10.1080/10406638.2021.1892779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Amany M. Ismail
- Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt
| | - Ian S. Butler
- Department of Chemistry, McGill University, Montreal, QC, Canada
| | | | - Sahar I. Mostafa
- Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt
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Tillmann M, Tang Q, Gardner G, Cohen JD. Complexity of the auxin biosynthetic network in Arabidopsis hypocotyls is revealed by multiple stable-labeled precursors. PHYTOCHEMISTRY 2022; 200:113219. [PMID: 35523282 DOI: 10.1016/j.phytochem.2022.113219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/22/2022] [Accepted: 04/25/2022] [Indexed: 06/14/2023]
Abstract
Auxin is a key regulator of plant development and in Arabidopsis thaliana can be synthesized through multiple pathways; however, the contributions of various biosynthetic pathways to specific developmental processes are largely unknown. To trace the involvement of various biosynthetic routes to indole-3-acetic acid (IAA) under conditions that induce adventitious root formation in Arabidopsis hypocotyls, we treated seedlings with three different stable isotope-labeled precursors ([13C6]anthranilate, [15N1]indole, and [13C3]serine) and monitored label incorporation into a number of proposed biosynthesis intermediates as well as IAA. We also employed inhibitors targeting tryptophan aminotransferases and flavin monooxygenases of the IPyA pathway, and treatment with these inhibitors differentially altered the labeling patterns from all three precursors into intermediate compounds and IAA. [13C3]Serine was used to trace utilization of tryptophan (Trp) and downstream intermediates by monitoring 13C incorporation into Trp, indole-3-pyruvic acid (IPyA), and IAA; most 13C incorporation into IAA was eliminated with inhibitor treatments, suggesting Trp-dependent IAA biosynthesis through the IPyA pathway is a dominant contributor to the auxin pool in de-etiolating hypocotyls that can be effectively blocked using chemical inhibitors. Labeling treatment with both [13C6]anthranilate and [15N1]indole simultaneously resulted in higher label incorporation into IAA through [15N1]indole than through [13C6]anthranilate; however, this trend was reversed in the proposed precursors that were monitored, with the majority of isotope label originating from [13C6]anthranilate. An even greater proportion of IAA became [15N1]-labeled compared to [13C6]-labeled in seedlings treated with IPyA pathway inhibitors, suggesting that, when the IPyA pathway is blocked, IAA biosynthesis from labeled indole may also come from an origin independent of the measured pool of Trp in these tissues.
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Affiliation(s)
- Molly Tillmann
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Alderman Hall, 1970 Folwell Ave, St. Paul, Minnesota, 55108, USA.
| | - Qian Tang
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Alderman Hall, 1970 Folwell Ave, St. Paul, Minnesota, 55108, USA.
| | - Gary Gardner
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Alderman Hall, 1970 Folwell Ave, St. Paul, Minnesota, 55108, USA.
| | - Jerry D Cohen
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, Alderman Hall, 1970 Folwell Ave, St. Paul, Minnesota, 55108, USA.
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Evidence from Co-expression Analysis for the Involvement of Amidase and INS in the Tryptophan-Independent Pathway of IAA Synthesis in Arabidopsis. Appl Biochem Biotechnol 2022; 194:4673-4682. [PMID: 35802240 DOI: 10.1007/s12010-022-04047-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2022] [Indexed: 12/16/2022]
Abstract
The reverse genetic approach has uncovered indole synthase (INS) as the first enzyme in the tryptophan (trp)-independent pathway of IAA synthesis. The importance of INS was reevaluated suggesting it may interact with tryptophan synthase B (TSB) and therefore involved in the trp-dependent pathway. Thus, the main aim of this study was to clarify the route of INS through the analysis of Arabidopsis genome. Analysis of the top 2000 co-expression gene lists in general and specific conditions shows that TSA is strongly positively co-expressed with TSB in general, hormone, and abiotic conditions with mutual ranks of 89, 38, and 180 respectively. Moreover, TSA is positively correlated with TSB (0.291). However, INS was not found in any of these coexpressed gene lists and negatively correlated with TSB (- 0.046) suggesting unambiguously that these two routes are separately and independently operated. So far, the remaining steps in the INS pathway have remained elusive. Among all enzymes reported to have a role in IAA synthesis, amidase was found to strongly positively co-expressed with INS in general and light conditions with mutual ranks of 116 and 141 respectively. Additionally, amidase1 was found to positively correlate with INS (0.297) and negatively coexpressed with TSB concluding that amidase may exclusively involve in the trp-independent pathway.
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Kebert M, Vuksanović V, Stefels J, Bojović M, Horák R, Kostić S, Kovačević B, Orlović S, Neri L, Magli M, Rapparini F. Species-Level Differences in Osmoprotectants and Antioxidants Contribute to Stress Tolerance of Quercus robur L., and Q. cerris L. Seedlings under Water Deficit and High Temperatures. PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11131744. [PMID: 35807695 PMCID: PMC9269681 DOI: 10.3390/plants11131744] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 05/13/2023]
Abstract
The general aim of this work was to compare the leaf-level responses of different protective components to water deficit and high temperatures in Quercus cerris L. and Quercus robur L. Several biochemical components of the osmotic adjustment and antioxidant system were investigated together with changes in hormones. Q. cerris and Q. robur seedlings responded to water deficit and high temperatures by: (1) activating a different pattern of osmoregulation and antioxidant mechanisms depending on the species and on the nature of the stress; (2) upregulating the synthesis of a newly-explored osmoprotectant, dimethylsulphoniopropionate (DMSP); (3) trading-off between metabolites; and (4) modulating hormone levels. Under water deficit, Q. cerris had a higher antioxidant capacity compared to Q. robur, which showed a lower investment in the antioxidant system. In both species, exposure to high temperatures induced a strong osmoregulation capacity that appeared largely conferred by DMSP in Q. cerris and by glycine betaine in Q. robur. Collectively, the more stress-responsive compounds in each species were those present at a significant basal level in non-stress conditions. Our results were discussed in terms of pre-adaptation and stress-induced metabolic patterns as related to species-specific stress tolerance features.
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Affiliation(s)
- Marko Kebert
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia; (M.K.); (S.K.); (B.K.); (S.O.)
| | - Vanja Vuksanović
- Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovića 8, 21000 Novi Sad, Serbia;
| | - Jacqueline Stefels
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands;
| | - Mirjana Bojović
- Faculty of Ecological Agriculture, Educons University, Vojvode Putnika 87, 21208 Sremska Kamenica, Serbia;
| | - Rita Horák
- Teacher Training Faculty in the Hungarian Language, University of Novi Sad, Subotica, Štrosmajerova 11, 24000 Subotica, Serbia;
| | - Saša Kostić
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia; (M.K.); (S.K.); (B.K.); (S.O.)
| | - Branislav Kovačević
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia; (M.K.); (S.K.); (B.K.); (S.O.)
| | - Saša Orlović
- Institute of Lowland Forestry and Environment, University of Novi Sad, Antona Čehova 13d, 21000 Novi Sad, Serbia; (M.K.); (S.K.); (B.K.); (S.O.)
| | - Luisa Neri
- Institute of BioEconomy (IBE), Department of Bio-Agrifood Science (DiSBA), National Research Council (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; (L.N.); (M.M.)
| | - Massimiliano Magli
- Institute of BioEconomy (IBE), Department of Bio-Agrifood Science (DiSBA), National Research Council (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; (L.N.); (M.M.)
| | - Francesca Rapparini
- Institute of BioEconomy (IBE), Department of Bio-Agrifood Science (DiSBA), National Research Council (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; (L.N.); (M.M.)
- Correspondence:
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Acosta K, Appenroth KJ, Borisjuk L, Edelman M, Heinig U, Jansen MAK, Oyama T, Pasaribu B, Schubert I, Sorrels S, Sree KS, Xu S, Michael TP, Lam E. Return of the Lemnaceae: duckweed as a model plant system in the genomics and postgenomics era. THE PLANT CELL 2021; 33:3207-3234. [PMID: 34273173 PMCID: PMC8505876 DOI: 10.1093/plcell/koab189] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 06/18/2021] [Indexed: 05/05/2023]
Abstract
The aquatic Lemnaceae family, commonly called duckweed, comprises some of the smallest and fastest growing angiosperms known on Earth. Their tiny size, rapid growth by clonal propagation, and facile uptake of labeled compounds from the media were attractive features that made them a well-known model for plant biology from 1950 to 1990. Interest in duckweed has steadily regained momentum over the past decade, driven in part by the growing need to identify alternative plants from traditional agricultural crops that can help tackle urgent societal challenges, such as climate change and rapid population expansion. Propelled by rapid advances in genomic technologies, recent studies with duckweed again highlight the potential of these small plants to enable discoveries in diverse fields from ecology to chronobiology. Building on established community resources, duckweed is reemerging as a platform to study plant processes at the systems level and to translate knowledge gained for field deployment to address some of society's pressing needs. This review details the anatomy, development, physiology, and molecular characteristics of the Lemnaceae to introduce them to the broader plant research community. We highlight recent research enabled by Lemnaceae to demonstrate how these plants can be used for quantitative studies of complex processes and for revealing potentially novel strategies in plant defense and genome maintenance.
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Affiliation(s)
- Kenneth Acosta
- Department of Plant Biology, Rutgers the State University of New Jersey, New Brunswick, NJ 08901, USA
| | - Klaus J Appenroth
- Plant Physiology, Matthias Schleiden Institute, University of Jena, Jena 07737, Germany
| | - Ljudmilla Borisjuk
- The Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben D-06466, Germany
| | - Marvin Edelman
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Uwe Heinig
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Marcel A K Jansen
- School of Biological, Earth and Environmental Sciences, Environmental Research Institute, University College Cork, Cork T23 TK30, Ireland
| | - Tokitaka Oyama
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Buntora Pasaribu
- Department of Plant Biology, Rutgers the State University of New Jersey, New Brunswick, NJ 08901, USA
| | - Ingo Schubert
- The Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben D-06466, Germany
| | - Shawn Sorrels
- Department of Plant Biology, Rutgers the State University of New Jersey, New Brunswick, NJ 08901, USA
| | - K Sowjanya Sree
- Department of Environmental Science, Central University of Kerala, Periye 671320, India
| | - Shuqing Xu
- Institute for Evolution and Biodiversity, University of Münster, Münster 48149, Germany
| | - Todd P Michael
- Plant Molecular and Cellular Biology Laboratory, The Salk Institute of Biological Studies, La Jolla, California 92037, USA
| | - Eric Lam
- Department of Plant Biology, Rutgers the State University of New Jersey, New Brunswick, NJ 08901, USA
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Tillmann M, Tang Q, Cohen JD. Protocol: analytical methods for visualizing the indolic precursor network leading to auxin biosynthesis. PLANT METHODS 2021; 17:63. [PMID: 34158074 PMCID: PMC8220744 DOI: 10.1186/s13007-021-00763-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 06/07/2021] [Indexed: 05/13/2023]
Abstract
BACKGROUND The plant hormone auxin plays a central role in regulation of plant growth and response to environmental stimuli. Multiple pathways have been proposed for biosynthesis of indole-3-acetic acid (IAA), the primary auxin in a number of plant species. However, utilization of these different pathways under various environmental conditions and developmental time points remains largely unknown. RESULTS Monitoring incorporation of stable isotopes from labeled precursors into proposed intermediates provides a method to trace pathway utilization and characterize new biosynthetic routes to auxin. These techniques can be aided by addition of chemical inhibitors to target specific steps or entire pathways of auxin synthesis. CONCLUSIONS Here we describe techniques for pathway analysis in Arabidopsis thaliana seedlings using multiple stable isotope-labeled precursors and chemical inhibitors coupled with highly sensitive liquid chromatography-mass spectrometry (LC-MS) methods. These methods should prove to be useful to researchers studying routes of IAA biosynthesis in vivo in a variety of plant tissues.
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Affiliation(s)
- Molly Tillmann
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, MN, USA.
| | - Qian Tang
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, MN, USA
| | - Jerry D Cohen
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, MN, USA
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Bishnu Maya K, Gauchan DP, Khanal SN, Chimouriya S, Lamichhane J. Amelioration of growth attributes of Bambusa nutans subsp. cupulata Stapleton by indole-3-acetic acid extracted from newly isolated Bacillus mesonae MN511751 from rhizosphere of Bambusa tulda Roxburgh. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2021. [DOI: 10.1016/j.bcab.2021.101920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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G. C, D.S. F, S. S, M. S, S. G. Indole-3-acetic acid/diol based pH-sensitive biological macromolecule for antibacterial, antifungal and antioxidant applications. Int J Biol Macromol 2017; 95:363-375. [DOI: 10.1016/j.ijbiomac.2016.11.068] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/26/2016] [Accepted: 11/19/2016] [Indexed: 11/15/2022]
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Chitra G, Franklin DS, Guhanathan S. Indole-3-acetic acid based tunable hydrogels for antibacterial, antifungal and antioxidant applications. JOURNAL OF MACROMOLECULAR SCIENCE PART A-PURE AND APPLIED CHEMISTRY 2017. [DOI: 10.1080/10601325.2017.1265401] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- G. Chitra
- Department of Chemistry, Periyar University, Salem, India
- Department of Chemistry, Bangalore College of Engineering and Technology, Bangalore, India
| | - D. S. Franklin
- Department of Chemistry, C. Abdul Hakeem College of Engineering and Technology, Melvisharam, India
| | - S. Guhanathan
- PG & Research Department of Chemistry, Muthurangam Government Arts College, Vellore, India
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12
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Nonhebel HM. Tryptophan-Independent Indole-3-Acetic Acid Synthesis: Critical Evaluation of the Evidence. PLANT PHYSIOLOGY 2015; 169:1001-5. [PMID: 26251310 PMCID: PMC4587473 DOI: 10.1104/pp.15.01091] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 08/03/2015] [Indexed: 05/08/2023]
Abstract
Evidence for Trp-independent IAA synthesis is critically reevaluated in the light of tryptophan synthase proteome data, local IAA synthesis and Trp, indole-3-pyruvate, and IAA turnover.
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Affiliation(s)
- Heather M Nonhebel
- School of Science and Technology, University of New England, Armidale, New South Wales 2350, Australia
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13
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Auxin and Tryptophan Homeostasis Are Facilitated by the ISS1/VAS1 Aromatic Aminotransferase in Arabidopsis. Genetics 2015; 201:185-99. [PMID: 26163189 DOI: 10.1534/genetics.115.180356] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 07/07/2015] [Indexed: 12/20/2022] Open
Abstract
Indole-3-acetic acid (IAA) plays a critical role in regulating numerous aspects of plant growth and development. While there is much genetic support for tryptophan-dependent (Trp-D) IAA synthesis pathways, there is little genetic evidence for tryptophan-independent (Trp-I) IAA synthesis pathways. Using Arabidopsis, we identified two mutant alleles of ISS1 ( I: ndole S: evere S: ensitive) that display indole-dependent IAA overproduction phenotypes including leaf epinasty and adventitious rooting. Stable isotope labeling showed that iss1, but not WT, uses primarily Trp-I IAA synthesis when grown on indole-supplemented medium. In contrast, both iss1 and WT use primarily Trp-D IAA synthesis when grown on unsupplemented medium. iss1 seedlings produce 8-fold higher levels of IAA when grown on indole and surprisingly have a 174-fold increase in Trp. These findings indicate that the iss1 mutant's increase in Trp-I IAA synthesis is due to a loss of Trp catabolism. ISS1 was identified as At1g80360, a predicted aromatic aminotransferase, and in vitro and in vivo analysis confirmed this activity. At1g80360 was previously shown to primarily carry out the conversion of indole-3-pyruvic acid to Trp as an IAA homeostatic mechanism in young seedlings. Our results suggest that in addition to this activity, in more mature plants ISS1 has a role in Trp catabolism and possibly in the metabolism of other aromatic amino acids. We postulate that this loss of Trp catabolism impacts the use of Trp-D and/or Trp-I IAA synthesis pathways.
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Hassan HA, El-Kholy WM, Nour SE. Proanthocyanidin as a cytogenetic protective agent against adverse effects of plant growth regulators supplementation in rats. Cytotechnology 2014; 66:585-96. [PMID: 23900525 PMCID: PMC4082783 DOI: 10.1007/s10616-013-9607-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 06/12/2013] [Indexed: 12/20/2022] Open
Abstract
The aim of the present study was to investigate the protective role of grape seed extract (containing proanthocyandin) against the adverse effects of plant growth regulators (GA3 (gibberellic acid) and IAA (indoleacetic acid)). The present data showed that the administration of either GA3 and IAA caused undesirable changes in both hepatic and testicular structure. This was evidenced by a disturbed hepatic strands, pyknotic nuclei, central vein with collapsed endothelium, dilatation in bile sinusoids, congested blood vessel, binucleatd hepatocytes, lymphocytic infiltration, vacuolation, giant hepatic cells, increased Kupffer cells and karyoryxis. Additionally, it was shown that degenerative changes in the testis, spermatogenic arrest, moderate tubular necrosis, Leydig cell degeneration and reduction in the number and size of the seminiferous tubules with some spermatogonia detached from the basement membrane. Concerning flow cytometric study of the liver a significant decrease in G0/1 % and a significant increase in S phase %, G2/M %, P(53) % and apoptosis % (sub G1) were detected. However, in testis the data recorded a significant decrease in the percentage of mature sperm (percentage of haploid cells) and a significant increase in the percentage of spermatide, diploid cells, P(53) and of apoptotic cells. On the other hand, a distinct recovery of the mentioned hepatic and testicular histopathological and cytogenetic disorders was observed when proanthocyanidin was supplemented to rats administered either of the plant growth hormones (GA3 and IAA).
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Affiliation(s)
- Hanaa A Hassan
- Physiology Division, Zoology Department, Faculty of Science, Mansoura University, Mansoura, Egypt,
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15
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Lituiev DS, Krohn NG, Müller B, Jackson D, Hellriegel B, Dresselhaus T, Grossniklaus U. Theoretical and experimental evidence indicates that there is no detectable auxin gradient in the angiosperm female gametophyte. Development 2014; 140:4544-53. [PMID: 24194471 DOI: 10.1242/dev.098301] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The plant life cycle alternates between a diploid sporophytic and a haploid gametophytic generation. The female gametophyte (FG) of flowering plants is typically formed through three syncytial mitoses, followed by cellularisation that forms seven cells belonging to four cell types. The specification of cell fates in the FG has been suggested to depend on positional information provided by an intrinsic auxin concentration gradient. The goal of this study was to develop mathematical models that explain the formation of this gradient in a syncytium. Two factors were proposed to contribute to the maintenance of the auxin gradient in Arabidopsis FGs: polar influx at early stages and localised auxin synthesis at later stages. However, no gradient could be generated using classical, one-dimensional theoretical models under these assumptions. Thus, we tested other hypotheses, including spatial confinement by the large central vacuole, background efflux and localised degradation, and investigated the robustness of cell specification under different parameters and assumptions. None of the models led to the generation of an auxin gradient that was steep enough to allow sufficiently robust patterning. This led us to re-examine the response to an auxin gradient in developing FGs using various auxin reporters, including a novel degron-based reporter system. In agreement with the predictions of our models, auxin responses were not detectable within the FG of Arabidopsis or maize, suggesting that the effects of manipulating auxin production and response on cell fate determination might be indirect.
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Affiliation(s)
- Dmytro S Lituiev
- Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
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Tivendale ND, Ross JJ, Cohen JD. The shifting paradigms of auxin biosynthesis. TRENDS IN PLANT SCIENCE 2014; 19:44-51. [PMID: 24524164 DOI: 10.1016/j.tplants.2013.09.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Auxins are an important group of hormones found in all land plants and several soil-dwelling microbes. Although auxin was the first phytohormone identified, its biosynthesis remained unclear until recently. In the past few years, our understanding of auxin biosynthesis has im-proved dramatically, to the stage where many believe there is a single predominant pathway in Arabidopsis (Arabidopsis thaliana L.). However, there is still uncertainty over the applicability of these findings to other plant species. Indeed, it appears that in certain organs of some species, other pathways can operate. Here we review the key advances that have led to our current understanding of auxin biosynthesis and its many pro-posed pathways.
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Abstract
Auxin is a plant hormone involved in an extraordinarily broad variety of biological mechanisms. These range from basic cellular processes, such as endocytosis, cell polarity, and cell cycle control over localized responses such as cell elongation and differential growth, to macroscopic phenomena such as embryogenesis, tissue patterning, and de novo formation of organs. Even though the history of auxin research reaches back more than a hundred years, we are still far from a comprehensive understanding of how auxin governs such a wide range of responses. Some answers to this question may lie in the auxin molecule itself. Naturally occurring auxin-like substances have been found and they may play roles in specific developmental and cellular processes. The molecular mode of auxin action can be further explored by the utilization of synthetic auxin-like molecules. A second area is the perception of auxin, where we know of three seemingly independent receptors and signalling systems, some better understood than others, but each of them probably involved in distinct physiological processes. Lastly, auxin is actively modified, metabolized, and intracellularly compartmentalized, which can have a great impact on its availability and activity. In this review, we will give an overview of these rather recent and emerging areas of auxin research and try to formulate some of the open questions. Without doubt, the manifold facets of auxin biology will not cease to amaze us for a long time to come.
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Affiliation(s)
- Michael Sauer
- Centro Nacional de Biotecnología-CNB-CSIC, Darwin 3, 28049 Madrid, Spain
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Bisewska J, Sarnowska EI, Tukaj ZH. Phytotoxicity and antioxidative enzymes of green microalga (Desmodesmus subspicatus) and duckweed (Lemna minor) exposed to herbicides MCPA, chloridazon and their mixtures. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2012; 47:814-822. [PMID: 22575008 DOI: 10.1080/03601234.2012.676443] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this study, we evaluate the toxicity of MCPA (auxin-like growth inhibitor), chloridazon (CHD) (PSII-inhibitor) and their mixtures to floating plants and planktonic algae. Toxicity of MCPA (4-chloro-2-methylphenoxyacetic acid) and CHD (5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone) was first assessed in two growth inhibition tests with Lemna minor (ISO/DIS 20079) and Desmodesmus subspicatus (ISO 8692). Next, herbicide mixtures at concentrations corresponding to the EC values were used to assess their interactive effects, and the biomarkers were: for duckweed fresh weight, frond area, chlorophyll content and number of fronds, and for algae cell count and cell volume. The 3d EC₁₀ and EC₅₀ values using cell counts of D. subspicatus were 142.7 and 529.1 mg/L for MCPA and 1.7 and 5.1 mg/L for CHD. The 7d EC₁₀ and EC₅₀ values using frond number of L. minor amounted to 0.8 and 5.4 mg/L for MCPA and 0.7 and 10.4 mg/L for CHD. Higher sensitivity of reproductive (number of cells/fronds) than growth processes (cell volume/frond area) to herbicides applied individually and in mixtures was especially pronounced in the responses of Desmodesmus. Herbicide interactions were assessed by the two-way ANOVA and Abbott's formula. Generally, an antagonistic interaction with Lemna was revealed by MCPA and chloridazon, whereas additive effect of both herbicides was observed for Desmodesmus. A significant stimulation of SOD and APX activity by binary mixtures was noted in algal cells mainly after 24 and 48 hours of exposure. The extremely high stimulation of the activity of both enzymes was induced by the combination EC₁₀CHD + EC₅₀MCPA (48 h). Presumably due to oxidative stress, the treatment with CHD at concentration EC₅₀ after 72 h was lethal for algae grown in aerated cultures, in contrast to standardized test conditions. Taking into account the consequences of risk assessment for herbicide mixtures we can state that a relatively low toxicity, as well as the lack of significant synergy between MCPA and CHD to non-target plants appears to be the most important result.
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Affiliation(s)
- Joanna Bisewska
- Department of Plant Physiology, University of Gdańsk, Gdynia, Poland
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Liu X, Hegeman AD, Gardner G, Cohen JD. Protocol: High-throughput and quantitative assays of auxin and auxin precursors from minute tissue samples. PLANT METHODS 2012; 8:31. [PMID: 22883136 PMCID: PMC3457856 DOI: 10.1186/1746-4811-8-31] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/16/2012] [Indexed: 05/04/2023]
Abstract
BACKGROUND The plant hormone auxin, indole-3-acetic acid (IAA), plays important roles in plant growth and development. The signaling response to IAA is largely dependent on the local concentration of IAA, and this concentration is regulated by multiple mechanisms in plants. Therefore, the precise quantification of local IAA concentration provides insights into the regulation of IAA and its biological roles. Meanwhile, pathways and genes involved in IAA biosynthesis are not fully understood, so it is necessary to analyze the production of IAA at the metabolite level for unbiased studies of IAA biosynthesis. RESULTS We have developed high-throughput methods to quantify plant endogenous IAA and its biosynthetic precursors including indole, tryptophan, indole-3-pyruvic acid (IPyA), and indole-3-butyric acid (IBA). The protocol starts with homogenizing plant tissues with stable-labeled internal standards added, followed by analyte purification using solid phase extraction (SPE) tips and analyte derivatization. The derivatized analytes are finally analyzed by selected reaction monitoring on a gas chromatograph-mass spectrometer (GC-MS/MS) to determine the precise abundance of analytes. The amount of plant tissue required for the assay is small (typically 2-10 mg fresh weight), and the use of SPE tips is simple and convenient, which allows preparation of large sets of samples within reasonable time periods. CONCLUSIONS The SPE tips and GC-MS/MS based method enables high-throughput and accurate quantification of IAA and its biosynthetic precursors from minute plant tissue samples. The protocol can be used for measurement of these endogenous compounds using isotope dilution, and it can also be applied to analyze IAA biosynthesis and biosynthetic pathways using stable isotope labeling. The method will potentially advance knowledge of the role and regulation of IAA.
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Affiliation(s)
- Xing Liu
- Plant Biological Sciences Graduate Program, Department of Horticultural Science, and Microbial and Plant Genomics Institute, University of Minnesota, 1970 Folwell Avenue, Saint Paul, MN, 55108, USA
- Division of Biology, 156–29, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Adrian D Hegeman
- Plant Biological Sciences Graduate Program, Department of Horticultural Science, and Microbial and Plant Genomics Institute, University of Minnesota, 1970 Folwell Avenue, Saint Paul, MN, 55108, USA
| | - Gary Gardner
- Plant Biological Sciences Graduate Program, Department of Horticultural Science, and Microbial and Plant Genomics Institute, University of Minnesota, 1970 Folwell Avenue, Saint Paul, MN, 55108, USA
| | - Jerry D Cohen
- Plant Biological Sciences Graduate Program, Department of Horticultural Science, and Microbial and Plant Genomics Institute, University of Minnesota, 1970 Folwell Avenue, Saint Paul, MN, 55108, USA
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Rosquete MR, Barbez E, Kleine-Vehn J. Cellular auxin homeostasis: gatekeeping is housekeeping. MOLECULAR PLANT 2012; 5:772-86. [PMID: 22199236 DOI: 10.1093/mp/ssr109] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The phytohormone auxin is essential for plant development and contributes to nearly every aspect of the plant life cycle. The spatio-temporal distribution of auxin depends on a complex interplay between auxin metabolism and cell-to-cell auxin transport. Auxin metabolism and transport are both crucial for plant development; however, it largely remains to be seen how these processes are integrated to ensure defined cellular auxin levels or even gradients within tissues or organs. In this review, we provide a glance at very diverse topics of auxin biology, such as biosynthesis, conjugation, oxidation, and transport of auxin. This broad, but certainly superficial, overview highlights the mutual importance of auxin metabolism and transport. Moreover, it allows pinpointing how auxin metabolism and transport get integrated to jointly regulate cellular auxin homeostasis. Even though these processes have been so far only separately studied, we assume that the phytohormonal crosstalk integrates and coordinates auxin metabolism and transport. Besides the integrative power of the global hormone signaling, we additionally introduce the hypothetical concept considering auxin transport components as gatekeepers for auxin responses.
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Affiliation(s)
- Michel Ruiz Rosquete
- Department of Applied Genetics and Cell Biology, University of Applied Life Sciences and Natural Resources (BOKU), 1190 Vienna, Austria
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21
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Interactive effects of temperature and heavy metals (Cd, Pb) on the elongation growth in maize coleoptiles. C R Biol 2012; 335:292-9. [DOI: 10.1016/j.crvi.2012.03.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/26/2012] [Accepted: 03/27/2012] [Indexed: 11/21/2022]
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Liu X, Cohen JD, Gardner G. Low-fluence red light increases the transport and biosynthesis of auxin. PLANT PHYSIOLOGY 2011; 157:891-904. [PMID: 21807888 PMCID: PMC3192557 DOI: 10.1104/pp.111.181388] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
In plants, light is an important environmental signal that induces photomorphogenesis and interacts with endogenous signals, including hormones. We found that light increased polar auxin transport in dark-grown Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum) hypocotyls. In tomato, this increase was induced by low-fluence red or blue light followed by 1 d of darkness. It was reduced in phyA, phyB1, and phyB2 tomato mutants and was reversed by far-red light applied immediately after the red or blue light exposure, suggesting that phytochrome is involved in this response. We further found that the free indole-3-acetic acid (IAA) level in hypocotyl regions below the hook was increased by red light, while the level of conjugated IAA was unchanged. Analysis of IAA synthesized from [¹³C]indole or [¹³C]tryptophan (Trp) revealed that both Trp-dependent and Trp-independent IAA biosynthesis were increased by low-fluence red light in the top section (meristem, cotyledons, and hook), and the Trp-independent pathway appears to become the primary route for IAA biosynthesis after red light exposure. IAA biosynthesis in tissues below the top section was not affected by red light, suggesting that the increase of free IAA in this region was due to increased transport of IAA from above. Our study provides a comprehensive view of light effects on the transport and biosynthesis of IAA, showing that red light increases both IAA biosynthesis in the top section and polar auxin transport in hypocotyls, leading to unchanged free IAA levels in the top section and increased free IAA levels in the lower hypocotyl regions.
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Affiliation(s)
- Xing Liu
- Plant Biological Sciences Graduate Program, Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, Minnesota 55108, USA.
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Fleischmann TT, Scharff LB, Alkatib S, Hasdorf S, Schöttler MA, Bock R. Nonessential plastid-encoded ribosomal proteins in tobacco: a developmental role for plastid translation and implications for reductive genome evolution. THE PLANT CELL 2011; 23:3137-55. [PMID: 21934145 PMCID: PMC3203423 DOI: 10.1105/tpc.111.088906] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 08/18/2011] [Accepted: 09/03/2011] [Indexed: 05/20/2023]
Abstract
Plastid genomes of higher plants contain a conserved set of ribosomal protein genes. Although plastid translational activity is essential for cell survival in tobacco (Nicotiana tabacum), individual plastid ribosomal proteins can be nonessential. Candidates for nonessential plastid ribosomal proteins are ribosomal proteins identified as nonessential in bacteria and those whose genes were lost from the highly reduced plastid genomes of nonphotosynthetic plastid-bearing lineages (parasitic plants, apicomplexan protozoa). Here we report the reverse genetic analysis of seven plastid-encoded ribosomal proteins that meet these criteria. We have introduced knockout alleles for the corresponding genes into the tobacco plastid genome. Five of the targeted genes (ribosomal protein of the large subunit22 [rpl22], rpl23, rpl32, ribosomal protein of the small subunit3 [rps3], and rps16) were shown to be essential even under heterotrophic conditions, despite their loss in at least some parasitic plastid-bearing lineages. This suggests that nonphotosynthetic plastids show elevated rates of gene transfer to the nuclear genome. Knockout of two ribosomal protein genes, rps15 and rpl36, yielded homoplasmic transplastomic mutants, thus indicating nonessentiality. Whereas Δrps15 plants showed only a mild phenotype, Δrpl36 plants were severely impaired in photosynthesis and growth and, moreover, displayed greatly altered leaf morphology. This finding provides strong genetic evidence that chloroplast translational activity influences leaf development, presumably via a retrograde signaling pathway.
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Affiliation(s)
| | | | | | | | | | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany
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Alim K, Frey E. Quantitative predictions on auxin-induced polar distribution of PIN proteins during vein formation in leaves. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 33:165-173. [PMID: 20571847 DOI: 10.1140/epje/i2010-10604-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 05/10/2010] [Indexed: 05/29/2023]
Abstract
The dynamic patterning of the plant hormone auxin and its efflux facilitator the PIN protein are the key regulators for the spatial and temporal organization of plant development. In particular auxin induces the polar localization of its own efflux facilitator. Due to this positive feedback, auxin flow is directed and patterns of auxin and PIN arise. During the earliest stage of vein initiation in leaves auxin accumulates in a single cell in a rim of epidermal cells from which it flows into the ground meristem tissue of the leaf blade. There the localized auxin supply yields the successive polarization of PIN distribution along a strand of cells. We model the auxin and PIN dynamics within cells with a minimal canalization model. Solving the model analytically we uncover an excitable polarization front that triggers a polar distribution of PIN proteins in cells. As polarization fronts may extend to opposing directions from their initiation site, we suggest a possible resolution to the puzzling occurrence of bipolar cells, thus we offer an explanation for the development of closed, looped veins. Employing non-linear analysis, we identify the role of the contributing microscopic processes during polarization. Furthermore, we deduce quantitative predictions on polarization fronts establishing a route to determine the up to now largely unknown kinetic rates of auxin and PIN dynamics.
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Affiliation(s)
- K Alim
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Ludwig-Maximilians-Universität, Theresienstr. 37, D-80333, München, Germany.
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Normanly J. Approaching cellular and molecular resolution of auxin biosynthesis and metabolism. Cold Spring Harb Perspect Biol 2010; 2:a001594. [PMID: 20182605 DOI: 10.1101/cshperspect.a001594] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
There is abundant evidence of multiple biosynthesis pathways for the major naturally occurring auxin in plants, indole-3-acetic acid (IAA), and examples of differential use of two general routes of IAA synthesis, namely Trp-dependent and Trp-independent. Although none of these pathways has been completely defined, we now have examples of specific IAA biosynthetic pathways playing a role in developmental processes by way of localized IAA synthesis, causing us to rethink the interactions between IAA synthesis, transport, and signaling. Recent work also points to some IAA biosynthesis pathways being specific to families within the plant kingdom, whereas others appear to be more ubiquitous. An important advance within the past 5 years is our ability to monitor IAA biosynthesis and metabolism at increasingly higher resolution.
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Affiliation(s)
- Jennifer Normanly
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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Quint M, Barkawi LS, Fan KT, Cohen JD, Gray WM. Arabidopsis IAR4 modulates auxin response by regulating auxin homeostasis. PLANT PHYSIOLOGY 2009; 150:748-58. [PMID: 19395411 PMCID: PMC2689969 DOI: 10.1104/pp.109.136671] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 04/20/2009] [Indexed: 05/17/2023]
Abstract
In a screen for enhancers of tir1-1 auxin resistance, we identified two novel alleles of the putative mitochondrial pyruvate dehydrogenase E1alpha-subunit, IAA-Alanine Resistant4 (IAR4). In addition to enhancing the auxin response defects of tir1-1, iar4 single mutants exhibit numerous auxin-related phenotypes including auxin-resistant root growth and reduced lateral root development, as well as defects in primary root growth, root hair initiation, and root hair elongation. Remarkably, all of these iar4 mutant phenotypes were rescued when endogenous indole-3-acetic acid (IAA) levels were increased by growth at high temperature or overexpression of the YUCCA1 IAA biosynthetic enzyme, suggesting that iar4 mutations may alter IAA homeostasis rather than auxin response. Consistent with this possibility, iar4 mutants exhibit increased Aux/IAA stability compared to wild type under basal conditions, but not in response to an auxin treatment. Measurements of free IAA levels detected no significant difference between iar4-3 and wild-type controls. However, we consistently observed significantly higher levels of IAA-amino acid conjugates in the iar4-3 mutant. Furthermore, using stable isotope-labeled IAA precursors, we observed a significant increase in the relative utilization of the Trp-independent IAA biosynthetic pathway in iar4-3. We therefore suggest that the auxin phenotypes of iar4 mutants are the result of altered IAA homeostasis.
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Affiliation(s)
- Marcel Quint
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108, USA
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27
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Chiappetta A, Fambrini M, Petrarulo M, Rapparini F, Michelotti V, Bruno L, Greco M, Baraldi R, Salvini M, Pugliesi C, Bitonti MB. Ectopic expression of LEAFY COTYLEDON1-LIKE gene and localized auxin accumulation mark embryogenic competence in epiphyllous plants of Helianthus annuus x H. tuberosus. ANNALS OF BOTANY 2009; 103:735-47. [PMID: 19151043 PMCID: PMC2707873 DOI: 10.1093/aob/mcn266] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 10/01/2008] [Accepted: 11/27/2008] [Indexed: 05/22/2023]
Abstract
BACKGROUND AND AIMS The clone EMB-2 of the interspecific hybrid Helianthus annuus x H. tuberosus provides an interesting system to study molecular and physiological aspects of somatic embryogenesis. Namely, in addition to non-epiphyllous (NEP) leaves that expand normally, EMB-2 produces epiphyllous (EP) leaves bearing embryos on the adaxial surface. This clone was used to investigate if the ectopic expression of H. annuus LEAFY COTYLEDON1-LIKE (Ha-L1L) gene and auxin activity are correlated with the establishment of embryogenic competence. METHODS Ha-L1L expression was evaluated by semi-quantitative RT-PCR and in situ hybridization. The endogenous level and spatial distribution of free indole-3-acetic acid (IAA) were estimated by a capillary gas chromatography-mass spectrometry-selected ion monitoring method and an immuno-cytochemical approach. KEY RESULTS Ectopic expression of Ha-L1L was detected in specific cell domains of the adaxial epidermis of EP leaves prior to the development of ectopic embryos. Ha-L1L was expressed rapidly when NEP leaves were induced to regenerate somatic embryos by in vitro culture. Differences in auxin distribution pattern rather than in absolute level were observed between EP and A-2 leaves. More precisely, a strong IAA immuno-signal was detected in single cells or in small groups of cells along the epidermis of EP leaves and accompanied the early stages of embryo development. Changes in auxin level and distribution were observed in NEP leaves induced to regenerate by in vitro culture. Exogenous auxin treatments lightly influenced Ha-L1L transcript levels in spite of an enhancement of the regeneration frequency. CONCLUSIONS In EP leaves, Ha-L1L activity marks the putative founder cells of ectopic embryos. Although the ectopic expression of Ha-L1L seems to be not directly mediated by auxin levels per se, it was demonstrated that localized Ha-L1L expression and IAA accumulation in leaf epidermis domains represent early events of somatic embryogenesis displayed by the epiphyllous EMB-2 clone.
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Affiliation(s)
- A. Chiappetta
- Università della Calabria, Dipartimento di Ecologia, Via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - M. Fambrini
- Università di Pisa, Dipartimento di Biologia delle Piante Agrarie – Sezione di Genetica, Via Matteotti 1B, I-56124 Pisa, Italy
| | - M. Petrarulo
- Università della Calabria, Dipartimento di Ecologia, Via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - F. Rapparini
- Consiglio Nazionale delle Ricerche, Istituto di Biometeorologia IBIMET – Sezione di Bologna, Via Gobetti 101, I-40129 Bologna, Italy
| | - V. Michelotti
- Università di Pisa, Dipartimento di Biologia delle Piante Agrarie – Sezione di Genetica, Via Matteotti 1B, I-56124 Pisa, Italy
| | - L. Bruno
- Università della Calabria, Dipartimento di Ecologia, Via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - M. Greco
- Università della Calabria, Dipartimento di Ecologia, Via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - R. Baraldi
- Consiglio Nazionale delle Ricerche, Istituto di Biometeorologia IBIMET – Sezione di Bologna, Via Gobetti 101, I-40129 Bologna, Italy
| | - M. Salvini
- Università di Pisa, Dipartimento di Biologia delle Piante Agrarie – Sezione di Genetica, Via Matteotti 1B, I-56124 Pisa, Italy
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56124 Pisa, Italy
| | - C. Pugliesi
- Università di Pisa, Dipartimento di Biologia delle Piante Agrarie – Sezione di Genetica, Via Matteotti 1B, I-56124 Pisa, Italy
| | - M. B. Bitonti
- Università della Calabria, Dipartimento di Ecologia, Via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
- For correspondence. E-mail
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Ehlert B, Schöttler MA, Tischendorf G, Ludwig-Müller J, Bock R. The paramutated SULFUREA locus of tomato is involved in auxin biosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:3635-47. [PMID: 18757490 PMCID: PMC2561159 DOI: 10.1093/jxb/ern213] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 07/23/2008] [Accepted: 07/24/2008] [Indexed: 05/23/2023]
Abstract
The tomato (Solanum lycopersicum) sulfurea mutation displays trans-inactivation of wild-type alleles in heterozygous plants, a phenomenon referred to as paramutation. Homozygous mutant plants and paramutated leaf tissue of heterozygous plants show a pigment-deficient phenotype. The molecular basis of this phenotype and the function of the SULFUREA gene (SULF) are unknown. Here, a comprehensive physiological analysis of the sulfurea mutant is reported which suggests a molecular function for the SULFUREA locus. It is found that the sulf mutant is auxin-deficient and that the pigment-deficient phenotype is likely to represent only a secondary consequence of the auxin deficiency. This is most strongly supported by the isolation of a suppressor mutant which shows an auxin overaccumulation phenotype and contains elevated levels of indole-3-acetic acid (IAA). Several lines of evidence point to a role of the SULF gene in tryptophan-independent auxin biosynthesis, a pathway whose biochemistry and enzymology is still completely unknown. Thus, the sulfurea mutant may provide a promising entry point into elucidating the tryptophan-independent pathway of IAA synthesis.
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Affiliation(s)
- Britta Ehlert
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Mark Aurel Schöttler
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Gilbert Tischendorf
- Freie Universität Berlin, Institut für Biologie, Pflanzenphysiologie, D-14195 Berlin, Germany
| | - Jutta Ludwig-Müller
- Institut für Botanik, Technische Universität Dresden, Zellescher Weg 20b, D-01062, Dresden, Germany
| | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
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Sivaci A, Yalcin I. The Seasonal Changes in Endogenous Levels of Indole-3-Acetic Acid, Gibberellic Acid, Zeatin and Abscisic Acid in Stems of Some Apple Varieties (Malus sylvestris Miller). ACTA ACUST UNITED AC 2008. [DOI: 10.3923/ajps.2008.319.322] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Kim JI, Sharkhuu A, Jin JB, Li P, Jeong JC, Baek D, Lee SY, Blakeslee JJ, Murphy AS, Bohnert HJ, Hasegawa PM, Yun DJ, Bressan RA. yucca6, a dominant mutation in Arabidopsis, affects auxin accumulation and auxin-related phenotypes. PLANT PHYSIOLOGY 2007; 145:722-35. [PMID: 17885085 PMCID: PMC2048792 DOI: 10.1104/pp.107.104935] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 09/10/2007] [Indexed: 05/17/2023]
Abstract
Auxin plays critical roles in many aspects of plant growth and development. Although a number of auxin biosynthetic pathways have been identified, their overlapping nature has prevented a clear elucidation of auxin biosynthesis. Recently, Arabidopsis (Arabidopsis thaliana) mutants with supernormal auxin phenotypes have been reported. These mutants exhibit hyperactivation of genes belonging to the YUCCA family, encoding putative flavin monooxygenase enzymes that result in increased endogenous auxin levels. Here, we report the discovery of fertile dominant Arabidopsis hypertall1-1D and hypertall1-2D (yucca6-1D, -2D) mutants that exhibit typical auxin overproduction phenotypic alterations, such as epinastic cotyledons, increased apical dominance, and curled leaves. However, unlike other auxin overproduction mutants, yucca6 plants do not display short or hairy root phenotypes and lack morphological changes under dark conditions. In addition, yucca6-1D and yucca6-2D have extremely tall (>1 m) inflorescences with extreme apical dominance and twisted cauline leaves. Microarray analyses revealed that expression of several indole-3-acetic acid-inducible genes, including Aux/IAA, SMALL AUXIN-UP RNA, and GH3, is severalfold higher in yucca6 mutants than in the wild type. Tryptophan (Trp) analog feeding experiments and catalytic activity assays with recombinant YUCCA6 indicate that YUCCA6 is involved in a Trp-dependent auxin biosynthesis pathway. YUCCA6:GREEN FLUORESCENT PROTEIN fusion protein indicates YUCCA6 protein exhibits a nonplastidial subcellular localization in an unidentified intracellular compartment. Taken together, our results identify YUCCA6 as a functional member of the YUCCA family with unique roles in growth and development.
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Affiliation(s)
- Jeong Im Kim
- Center for Plant Environmental Stress Physiology , Purdue University, West Lafayette, Indiana 47906-2010, USA
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31
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Park S, Cohen JD, Slovin JP. Strawberry fruit protein with a novel indole-acyl modification. PLANTA 2006; 224:1015-22. [PMID: 16683161 DOI: 10.1007/s00425-006-0287-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Accepted: 04/02/2006] [Indexed: 05/09/2023]
Abstract
Achenes and receptacle tissue of Fragaria vesca, L. cultivar Yellow Wonder were shown to contain conjugated indole-3-acetic acid (IAA) that was not soluble in organic solvents and yielded IAA after strong alkaline hydrolysis, suggestive of IAA attached to plant proteins. This solvent insoluble conjugated IAA accounted for between 0.4 and 4 ng of IAA per gram fresh weight of tissue in both achenes and receptacles. To investigate this strawberry conjugate class further, a polyclonal antibody was produced to IAA-glycine attached to BSA that detected neutral indole acid esters, monocarboxylic-amino acid IAA conjugates and IAA proteins. Using immunoblotting, both achenes and receptacles of strawberry were shown to have primarily an immuno-detectable band at 76 kDa. Two-dimensional polyacrylamide gel electrophoresis yielded a wide band that was analyzed by LC-MS/MS analysis following in-gel trypsin digestion. Peptides derived from the immuno-detectable band were tentatively identified by peptide fragment analysis as being from either a chaperonin related to the hsp60 class of proteins or, alternatively, an ATP synthase. This is one of the first reports of an IAA modified protein in fruit tissue.
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Affiliation(s)
- Seijin Park
- Department of Horticultural Science and Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, MN 55108, USA
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Fujita H, Mochizuki A. Pattern formation of leaf veins by the positive feedback regulation between auxin flow and auxin efflux carrier. J Theor Biol 2006; 241:541-51. [PMID: 16510156 DOI: 10.1016/j.jtbi.2005.12.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Revised: 12/13/2005] [Accepted: 12/16/2005] [Indexed: 10/25/2022]
Abstract
The generation of vascular pattern formation in plants is an interesting process of pattern formation in organisms. It is well known that the plant hormone auxin is involved in plant vascular differentiation and that the PIN1 protein, an auxin efflux carrier, localizes to one side of the cell membrane. Several hypotheses have been proposed to explain the formation of leaf venation. One is the canalization hypothesis that is based on the assumption that a positive feedback regulation exists between the flow of a signal molecule and the capacity of its flow. Here, we attempted to integrate the canalization hypothesis and experimental data. We investigated models of the positive feedback regulation between the auxin flow and PIN1 localization. Model 1, with conserved PIN1 amount in each cell, can generate a branching pattern similar to that of plant leaf venation. We introduced the diffusible enhancer "e" into the model as unknown factor. The obtained patterns show a quasi-periodic distribution of auxin flow paths, when the model dynamics includes domain growth. In order to understand the early initiation process that generates an inhomogeneity from an almost homogeneous distribution, we introduced model 2, a simplified version of model 1. Model 2 can generate inhomogeneity with a parameter dependency similar to that of model 1. To analyse parameter condition required for pattern development, approximated equations are obtained from model 2. The isocline analysis of the equations without spatial structure shows that the inhomogeneous distribution occurs from an almost homogeneous distribution. This parameter condition for generating inhomogeneity is consistent with the results of models 1 and 2.
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Affiliation(s)
- Hironori Fujita
- Division of Theoretical Biology, National Institute for Basic Biology, Okazaki 444-8787, Japan.
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Huang C, Liu LY, Song TS, Ni L, Yang L, Hu XY, Hu JS, Song LP, Luo Y, Si LS. Apoptosis of pancreatic cancer BXPC-3 cells induced by indole-3-acetic acid in combination with horseradish peroxidase. World J Gastroenterol 2005; 11:4519-23. [PMID: 16052681 PMCID: PMC4398701 DOI: 10.3748/wjg.v11.i29.4519] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the mechanisms underlying the apoptosis of human pancreatic cancer BXPC-3 cells induced by indole-3-acetic acid (IAA) in combination with horseradish peroxidase (HRP).
METHODS: BXPC-3 cells derived from human pancreatic cancer were exposed to 40 or 80 µmol/L IAA and 1.2 µg/mL HRP at different times. Then, MTT assay was used to detect the cell proliferation. Flow cytometry was performed to analyze cell cycle. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was used to detect apoptosis. 2,7-Dichlorofluorescin diacetate uptake was measured by confocal microscopy to determine free radicals. Level of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) were measured by biochemical methods.
RESULTS: IAA/HRP initiated growth inhibition of BXPC-3 cells in a dose- and time-dependent manner. Flow cytometry revealed that the cells treated for 48 h were arrested at G1/G0. After exposure to 80 µmol/L IAA plus 1.2 µg/mL HRP for 72 h, the apoptosis rate increased to 72.5, which was nine times that of control. Content of MDA and activity of SOD increased respectively after treatment compared to control. Meanwhile, IAA/HRP stimulated the formation of free radicals.
CONCLUSION: The combination of IAA and HRP can inhibit the growth of human pancreatic cancer BXPC-3 cells in vitro by inducing apoptosis.
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Affiliation(s)
- Chen Huang
- Department of Cytobiology and Medical Genetics, College of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
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De Melo MP, Pithon-Curi TC, Curi R. Indole-3-acetic acid increases glutamine utilization by high peroxidase activity-presenting leukocytes. Life Sci 2004; 75:1713-25. [PMID: 15268971 DOI: 10.1016/j.lfs.2004.03.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2003] [Accepted: 03/29/2004] [Indexed: 10/26/2022]
Abstract
Indole-3-acetic acid (IAA) is toxic for human tumor cells and in association with horseradish peroxidase (HRP) can be used as a new prodrug/enzyme combination for targeted cancer therapy. The toxic effect of IAA on neutrophils, macrophages and lymphocytes is associated with cell peroxidase activity, which is high in neutrophils and low in lymphocytes. The effect of IAA on glucose and glutamine metabolism in leukocytes presenting different peroxidase activities: neutrophils, thioglycollate-elicited macrophages and lymphocytes was investigated. A time-course effect (from 6 to 48 h in culture) of IAA on glucose and glutamine metabolism of neutrophils, thioglycollate-elicited macrophages, and lymphocytes was then carried out. Addition of IAA (0.25 mM) did not have a marked effect on glucose utilization and lactate formation by the three cell types but it raised glutamine consumption and glutamate production by neutrophils and macrophages. IAA had no effect on glutamine consumption and glutamate production by lymphocytes. A strong relationship was found between glutamine utilization (0.999) and glutamate production (0.999) and peroxidase activity. IAA did not change the activities of hexokinase, glucose-6-phosphate dehydrogenase, citrate synthase, lactate dehydrogenase, and phosphate-dependent glutaminase of 24 h cultured neutrophils and lymphocytes. The effect of IAA (1 mM) on glucose and glutamine metabolism was also investigated by 1 h incubated leukocytes in PBS. IAA did not affect glucose and glutamine metabolism of lymphocytes but enhanced glucose and glutamine metabolism by 1 h incubated neutrophils and thioglycollate-elicited macrophages. IAA caused a marked increase on oxygen consumption by neutrophils, which was more pronounced in the presence of the glutamine as compared to glucose. The stimulation of oxygen consumption leads to a reduction in NADH/NAD+ ratio that activates the flux of substrates through the Krebs cycle. Since glutamine is mainly metabolized through the left hand side of the Krebs cycle, a reduction in the redox state of the cells may accelerate the flux of substrates through glutaminolysis. The toxic results presented here show that the affect of IAA in association with peroxidase involves activation of glutamine metabolism.
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Affiliation(s)
- Mariza P De Melo
- Department of Basic Science, Faculty of Zootechny and Food Engineering (FZEA), University of São Paulo, Pirassununga, Brazil.
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Renaudin JP. Growth and Physiology of Suspension-Cultured Plant Cells: the Contribution of Tobacco BY-2 Cells to the Study of Auxin Action. TOBACCO BY-2 CELLS 2004. [DOI: 10.1007/978-3-662-10572-6_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Kanyuka K, Praekelt U, Franklin KA, Billingham OE, Hooley R, Whitelam GC, Halliday KJ. Mutations in the huge Arabidopsis gene BIG affect a range of hormone and light responses. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:57-70. [PMID: 12834402 DOI: 10.1046/j.1365-313x.2003.01779.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In independent genetic screens, for shade-avoidance response and cytokinin sensitivity, we identified two Arabidopsis mutants, attenuated shade avoidance 1 (asa1) and umbrella1 (umb1), which have very similar pleiotropic phenotypes. asa1 and umb1 are allelic to tir3-1, and are caused by mutations in BIG, which is required for normal auxin efflux. They have a compact rosette, fewer lateral roots, delayed flowering, more secondary inflorescence, smaller seeds and, in the Laer-0 background, much shorter internodes between adjacent flowers, suggesting an interaction between BIG and ERECTA. These mutants have organ-specific defects in response to cytokinins, ethylene, N-1-naphthylphthalamic acid (NPA) and gibberellin (GA). The phenotype of the asa1 ga1-3 double mutant is consistent with defects in GA signalling. There are subtle effects in responses to auxins, abscisic acid and brassinolide. Elongation growth associated with shade avoidance in phyA phyB null mutants is suppressed by asa1 in all organs other than the hypocotyl. Therefore, we here provide evidence that BIG is a key player not just in auxin signalling, but in a multitude of light and hormone pathways.
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Cohen JD, Slovin JP, Hendrickson AM. Two genetically discrete pathways convert tryptophan to auxin: more redundancy in auxin biosynthesis. TRENDS IN PLANT SCIENCE 2003; 8:197-9. [PMID: 12758033 DOI: 10.1016/s1360-1385(03)00058-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The answer to the simple question of how plants make auxin has proven to be inordinately complex. Recent in planta studies in Arabidopsis have uncovered additional complexity in auxin biosynthesis. Two distinct pathways from tryptophan to the intermediate indoleacetaldoxime were identified. Genic, as well as functional redundancy, appear to be characteristic for auxin biosynthesis and plants might have evolved many different solutions for making and regulating auxin.
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Affiliation(s)
- Jerry D Cohen
- Department of Horticultural Science, University of Minnesota, Saint Paul, MN 55108, USA.
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38
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Zhao Y, Hull AK, Gupta NR, Goss KA, Alonso J, Ecker JR, Normanly J, Chory J, Celenza JL. Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3. Genes Dev 2002; 16:3100-12. [PMID: 12464638 PMCID: PMC187496 DOI: 10.1101/gad.1035402] [Citation(s) in RCA: 431] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the two Arabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and show growth defects consistent with partial auxin deficiency. Together with previous work on YUCCA, a flavin monooxygenase also implicated in IAOx production, and nitrilases that convert indole-3-acetonitrile to auxin, this work provides a framework for further dissecting auxin biosynthetic pathways and their regulation.
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Affiliation(s)
- Yunde Zhao
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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