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Jameson PE. Zeatin: The 60th anniversary of its identification. PLANT PHYSIOLOGY 2023; 192:34-55. [PMID: 36789623 PMCID: PMC10152681 DOI: 10.1093/plphys/kiad094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 02/06/2023] [Accepted: 02/08/2023] [Indexed: 05/03/2023]
Abstract
While various labs had shown cell division-inducing activity in a variety of plant extracts for over a decade, the identification of zeatin (Z) in 1964, the first known naturally occurring cytokinin, belongs to Letham and co-workers. Using extracts from maize (Zea mays), they were the first to obtain crystals of pure Z and in sufficient quantity for structural determination by MS, NMR, chromatography, and mixed melting-point analysis. This group also crystallized Z-9-riboside (ZR) from coconut (Cocos nucifera) milk. However, their chemical contributions go well beyond the identification of Z and ZR and include two unambiguous syntheses of trans-Z (to establish stereochemistry), the synthesis of 3H-cytokinins that facilitated metabolic studies, and the synthesis of deuterated internal standards for accurate mass spectral quantification. Letham and associates also unequivocally identified Z nucleotide, the 7-and 9-glucoside conjugates of Z, and the O-glucosides of Z, ZR, dihydro Z (DHZ) and DHZR as endogenous compounds and as metabolites of exogenous Z. Their contributions to the role of cytokinins in plant physiology and development were also substantial, especially the role of cytokinins moving in the xylem. These biological advances are described and briefly related to the genetic/molecular biological contributions of others that established that plants have an absolute requirement for cytokinin.
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Affiliation(s)
- Paula Elizabeth Jameson
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
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2
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Hallmark HT, Rashotte AM. Cytokinin isopentenyladenine and its glucoside isopentenyladenine-9G delay leaf senescence through activation of cytokinin-associated genes. PLANT DIRECT 2020; 4:e00292. [PMID: 33364544 PMCID: PMC7751127 DOI: 10.1002/pld3.292] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 11/08/2020] [Accepted: 11/12/2020] [Indexed: 06/01/2023]
Abstract
Cytokinins (CKs) are well-known as a class of phytohormones capable of delaying senescence in detached leaves. However, CKs are often treated as a monolithic group of compounds even though dozens of CK species are present in plants with varied degrees of reported biological activity. One specific type of CK, isopentenyladenine base (iP), has been demonstrated as having roles in delaying leaf senescence, inhibition of root growth, and promoting shoot regeneration. However, its N-glucosides isopentenyladenine-7- and -9-glucoside (iP7G, iP9G) have remained understudied and thought of as inactive cytokinins for several decades, despite their relatively high concentrations in plants such as the model species Arabidopsis thaliana. Here we show that iP and one of its glucosides, iP9G, are capable of delaying senescence in leaves, though the glucosides having little to no activity in other bioassays. Additionally, we performed the first transcriptomic study of iP-delayed cotyledon senescence which shows that iP is capable of upregulating photosynthetic genes and downregulating catabolic genes in detached cotyledons. Transcriptomic analysis also shows iP9G has limited effects on gene expression, but that the few affected genes are CK-related and are similar to those seen from iP effects during senescence as seen for the type-A response regulator ARR6. These findings suggest that iP9G functions as an active CK during senescence.
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Hallmark HT, Černý M, Brzobohatý B, Rashotte AM. trans-Zeatin-N-glucosides have biological activity in Arabidopsis thaliana. PLoS One 2020; 15:e0232762. [PMID: 32379789 PMCID: PMC7205299 DOI: 10.1371/journal.pone.0232762] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 04/21/2020] [Indexed: 11/22/2022] Open
Abstract
Cytokinin is an indispensable phytohormone responsible for physiological processes ranging from root development to leaf senescence. The term "cytokinin" refers to several dozen adenine-derived compounds occurring naturally in plants. Cytokinins (CKs) can be divided into various classes and forms; base forms are generally considered to be active while highly abundant cytokinin-N-glucosides (CKNGs), composed of a CK base irreversibly conjugated to a glucose molecule, are considered inactive. However, results from early CK studies suggest CKNGs do not always lack activity despite the perpetuation over several decades in the literature that they are inactive. Here we show that exogenous application of trans-Zeatin-N-glucosides (tZNGs, a specific class of CKNGs) to Arabidopsis results in CK response comparable to the application of an active CK base. These results are most apparent in senescence assays where both a CK base (tZ) and tZNGs (tZ7G, tZ9G) delay senescence in cotyledons. Further experiments involving root growth and shoot regeneration revealed tZNGs do not always have the same effects as tZ, and have largely distinct effects on the transcriptome and proteome. These data are in contrast to previous reports of CKNGs being inactive and raise questions about the function of these compounds as well as their mechanism of action.
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Affiliation(s)
- H. Tucker Hallmark
- Department of Biological Sciences, Auburn University, Auburn, AL, United States of America
| | - Martin Černý
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, Brno, Czech Republic
| | - Břetislav Brzobohatý
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, Brno, Czech Republic
| | - Aaron M. Rashotte
- Department of Biological Sciences, Auburn University, Auburn, AL, United States of America
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, Brno, Czech Republic
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Mens C, Li D, Haaima LE, Gresshoff PM, Ferguson BJ. Local and Systemic Effect of Cytokinins on Soybean Nodulation and Regulation of Their Isopentenyl Transferase ( IPT) Biosynthesis Genes Following Rhizobia Inoculation. FRONTIERS IN PLANT SCIENCE 2018; 9:1150. [PMID: 30135694 PMCID: PMC6092703 DOI: 10.3389/fpls.2018.01150] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Accepted: 07/18/2018] [Indexed: 05/12/2023]
Abstract
Cytokinins are important regulators of cell proliferation and differentiation in plant development. Here, a role for this phytohormone group in soybean nodulation is shown through the exogenous application of cytokinins (6-benzylaminopurine, N6-(Δ2-isopentenyl)-adenine and trans-zeatin) via either root drenching or a petiole feeding technique. Overall, nodule numbers were reduced by treatment with high cytokinin concentrations, but increased with lower concentrations. This was especially evident when feeding the solutions directly into the vasculature via petiole feeding. These findings highlight the importance of cytokinin in nodule development. To further investigate the role of cytokinin in controlling nodule numbers, the IPT gene family involved in cytokinin biosynthesis was characterized in soybean. Bioinformatic analyses identified 17 IPT genes in the soybean genome and homeologous duplicate gene partners were subsequently identified including GmIPT5 and GmIPT6, the orthologs of LjIPT3. Expression of GmIPT5 was upregulated in the shoot in response to nodulation, but this was independent of a functional copy of the autoregulation of nodulation (AON) receptor, GmNARK, which suggests it is unlikely to have a role in the negative feedback system called AON. Legumes also control nodule numbers in the presence of soil nitrogen through nitrate-dependent regulation of nodulation, a locally acting pathway in soybean. Upon nitrate treatment to the root, the tandem duplicates GmIPT3 and GmIPT15 were upregulated in expression indicating a role for these genes in the plant's response to soil nitrogen, potentially including the nitrate-dependent regulation of legume nodulation pathway. Additional roles for cytokinin and their IPT biosynthetic genes in nodulation and the control of nodule numbers are discussed.
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Affiliation(s)
| | | | | | | | - Brett J. Ferguson
- Centre for Integrative Legume Research, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD, Australia
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5
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Zhang W, He L, Zhang R, Guo S, Yue H, Ning X, Tan G, Li QX, Wang B. Development of a monoclonal antibody-based enzyme-linked immunosorbent assay for the analysis of 6-benzylaminopurine and its ribose adduct in bean sprouts. Food Chem 2016; 207:233-8. [DOI: 10.1016/j.foodchem.2016.03.103] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 03/27/2016] [Accepted: 03/28/2016] [Indexed: 10/22/2022]
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6
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The Identity of the Major Metabolite of Benzylaminopurine in Soybean Cultures, and the Inhibition of Its Formation by Aminophylline. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/s0304-4211(82)80005-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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7
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ytokinins and Changes in Their Activity During the Development of Grains of Wheat (Triticum aestivum L.). ACTA ACUST UNITED AC 1982. [DOI: 10.1016/s0044-328x(82)80051-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Parker CW, Letham DS, Gollnow BI, Summons RE, Duke CC, Macleod JK. Regulators of cell division in plant tissues : XXV. Metabolism of zeatin by lupin seedlings. PLANTA 1978; 142:239-251. [PMID: 24408185 DOI: 10.1007/bf00385073] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/1978] [Accepted: 05/30/1978] [Indexed: 06/03/2023]
Abstract
[(3)H]zeatin was supplied through the transpiration stream to de-rooted lupin (Lupinus angustifolius L.) seedlings. The following previously known metabolites were identified chromatographically: 5'-phosphates of zeatin riboside and dihydrozeatin riboside, adenosine-5'-phosphate, zeatin riboside, zeatin-7-glucopyranoside, zeatin-9-glucopyranoside, adenine, adenosine and dihydrozeatin. Five new metabolites were purified; four of these contain an intact zeatin moiety. Two were identified unequivocally, one as L-β-[6-(4-hydroxy-3-methylbut-trans-2-enylamino)-purin-9-yl]alanine, a metabolite now termed lupinic acid, and the second as O-β-D-glucopyranosylzeatin. These two compounds were the major metabolites formed when zeatin solution (100 μM) was supplied to the de-rooted seedlings. The radioactivity in the xylem sap of intact seedlings, supplied with [(3)H]zeatin via the roots, was largely due to zeatin, dihydrozeatin and zeatin riboside. When [(3)H]zeatin (5 μM) was supplied via the transpiration stream to de-rooted Lupinus luteus L. seedlings, the principal metabolite in the lamina was adenosine, while in the stem nucleotides of zeatin and adenine were the dominant metabolites. O-Glucosylzeatin and lupinic acid were also detected as metabolites. The level of the latter varied greatly in the tissues of the shoot, and was greatest in the lower region of the stem and in the expanding lamina. Minor metabolites also detected chromatographically were: (a) dihydrolupinic acid, (b) a partially characterized metabolite which appears to be a 9-substituted adenine (also formed in L. angustifolius), (c) glucosides of zeatin riboside and/or dihydrozeatin riboside, and (d) O-glucosyldihydrozeatin. While lupinic acid supplied exogenously to L. luteus leaves underwent little metabolism, chromatographic studies indicated that O-glucosylzeatin was converted to its riboside, the principal metabolite formed, and also to adenosine, zeatin and dihydrozeatin. A thinlayer chromatography procedure for separating zeatin, dihydrozeatin, zeatin riboside and dihydrozeatin riboside is described.
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Affiliation(s)
- C W Parker
- Research School of Biological Sciences, Australian National University, P.O. Box 475, 2601, Canberra City, A.C.T., Australia
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Gawer M, Laloue M, Terrine C, Guern J. Metabolism and biological significance of benzyladenine-7-glucoside. ACTA ACUST UNITED AC 1977. [DOI: 10.1016/0304-4211(77)90192-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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13
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Laloue M. Cytokinins: 7-glucosylation is not a prerequisite of the expression of their biological activity. PLANTA 1977; 134:273-275. [PMID: 24419782 DOI: 10.1007/bf00384193] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/1976] [Accepted: 12/03/1976] [Indexed: 06/03/2023]
Abstract
(14)C-labelled benzyladenine-7-glucoside (0.57 μM) supplied to cytokinin-requiring Nicotiana tabacum (cv. Wisconsin 38) cells cultivated in liquid medium was slowly absorbed and resulted in rather large intracellular quantities of benzyladenine-7-glucoside (30 pmol/10(5) cells) but did not show any biological activity, while 0.01 μM benzyladenosine induced cell division. In this case the resulting intracellular quantity of benzyladenine-7-glucoside formed was 3.3 pmol/10(5) cells. Also, N(6)-(Δ(2)-isopentenyl)adenosine induced cell division in these tobacco suspensions without being significantly 7-glucosylated. These data provide strong evidence that the 7-glucosylation of cytokinins is not a prerequisite of the expression of their biological activity.
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Affiliation(s)
- M Laloue
- Laboratoire de Physiologie végétale, Service des Hormones végétales, t.53.E.3., Université Pierre et Marie Curie, 4, place Jussieu, F-75230, Paris Cédex 05, France
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Hecht SM, Frye RB, Werner D, Hawrelak SD, Skoog F, Schmitz RY. On the "activation" of cytokinins. J Biol Chem 1975. [DOI: 10.1016/s0021-9258(19)40950-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Cowley D, Jenkins I, MacLeod J, Summons R, Letham D, Wilson M, Parker C. Structure and synthesis of unusual cytokinin metabolites. Tetrahedron Lett 1975. [DOI: 10.1016/s0040-4039(00)72631-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Iwamura H, Ito T, Kumazawa Z, Ogawa Y. Anticytokinin activity of 4-furfurylamino-7-(beta-D-ribofuranosyl)pyrrolo(2,3)pyrimidine. Biochem Biophys Res Commun 1974; 57:412-6. [PMID: 4829402 DOI: 10.1016/0006-291x(74)90946-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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18
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LEONARD NELSONJ. Chemistry of the Cytokinins. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/b978-0-12-612407-1.50008-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Hewett EW, Wareing PF. Cytokinins in Populus x robusta Schneid: A complex in leaves. PLANTA 1973; 112:225-233. [PMID: 24468731 DOI: 10.1007/bf00385326] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/1973] [Indexed: 06/03/2023]
Abstract
At least seven cytokinins have been detected in mature leaves of Populus x robusta Schneid after chromatography on Sephadex LH-20. Two of these have similar elution volumes to zeatin and zeatin riboside. A third appears to be a cytokinin glucoside. A fourth is a new, unidentified cytokinin, susceptible to mild oxidation, and yielding two cytokinin active products after acid hydrolysis. This cytokinin complex has been found in fully expanded leaves, a tissue in which cell division is completed.
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Affiliation(s)
- E W Hewett
- Department of Botany and Microbiology, University College of Wales, SY23 3DA, Aberystwyth, UK
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Parker CW, Letham DS. Regulators of cell division in plant tissues. XVI : Metabolism of zeatin by radish cotyledons and hypocotyls. PLANTA 1973; 114:199-218. [PMID: 24458755 DOI: 10.1007/bf00389036] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/1973] [Indexed: 06/03/2023]
Abstract
[(3)H]Zeatin was supplied through the transpiration stream to radish (Raphanus sativus L.) seedlings with roots excised. Formation of dihydrozeatin was not detected but numerous other metabolites were formed, including adenine, adenosine, AMP, zeatin riboside and zeatin riboside-5'-monophosphate. However, in labelled seedlings which had been left in water for 15 h, an unknown compound (raphanatin) was the dominant metabolite and accounted for about 25% of the total radioactivity extracted. A procedure for the isolation of this metabolite was devised and yielded 70 μg from 1600 seedlings. Raphanatin was characterized by mass and ultraviolet spectra and has been identified as 7-glucosylzeatin. It is an active and very stable metabolite which was located mainly in the cotyledon laminae and may be a storage form of the hormone. In contrast, labelled nucleotides, the other major metabolites of zeatin, were largely confined to the hypocotyls and petioles. Zeatin riboside-5'-monophosphate was the dominant metabolite in hypocotyls of de-rooted seedlings supplied with zeatin for 0.5-2 h. The majority of the radioactivity in the xylem sap was due to zeatin, but about 10% was present as zeatin riboside; nucleotides accounted for less than 10% of the radioactivity and labelled raphanatin was not detected.
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Affiliation(s)
- C W Parker
- Research School of Biological Sciences, Australian National University, P.O.B. 475, 2601, Canberra, A.C.T., Australia
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