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Carlos O. Miller

Bio: Carlos O. Miller is an academic researcher from Indiana University. The author has contributed to research in topics: Zeatin & Kinetin. The author has an hindex of 18, co-authored 27 publications receiving 1400 citations.
Topics: Zeatin, Kinetin, Cytokinin, Callus, Respiration

Papers
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Journal ArticleDOI
TL;DR: Evidence is presented strongly indicating that zeatin does occur naturally in its unsubstituted form and also in nucleoside and nucleotide forms and still a high degree of reproducibility from test to test.
Abstract: Three laboratories previously have obtained from Zea mays kernels (milk stage) one or more 6-(substituted)aminopurines capable of greatly promoting cell division in plant tissue cultures.1-3 At least two of the laboratories have worked on a single compound4 which has been identified as 6-(4-hydroxy-3-methylbut-2-enyl)aminopurine.5 The name zeatin has been applied to this particular compound.6 Only a small portion of the total cell-division activity in crude extracts from kernels seems to be due to zeatin'-3 and its actual existence in the kernel has been questioned.7 We now present evidence strongly indicating that zeatin does occur naturally in its unsubstituted form and also in nucleoside and nucleotide forms. Assay.-The active materials in the maize extracts were detected by using the soybean (Glycine max, var. Acme) tissue test.3' 8 This tissue requires a substance like zeatin for continued cell division and has proved to be very sensitive to zeatin and similar compounds. For example, in recent tests we have obtained measurable growth responses to as little as 5 X 10-11 M zeatin. Most assays were performed with small quantities of extracts which contained rather low concentrations of active materials. With such low concentrations, the soybean test shows considerable variation of fresh weights for individual pieces in a particular assay but still a high degree of reproducibility from test to test. Repeats of all experiments reported here have given consistent results. Stock cultures of the soybean tissue have been maintained on a medium containing (mg/liter): KH2PO4, 300; KNO3, 1000; NH4NO3, 1000; Ca(NO3)2 .4H20, 500; MgSO4-7H20, 71.5; KCl, 65; MnSO4 .4H20, 14; NaFe ethylenediaminetetraacetate, 13.2; ZnSO4 7H20, 3.8; H3BO3, 1.6; Cu(NO3)2.3H20, 0.35; (NH4)6 Mo7024 *4H20, 0.1; i-inositol, 100; nicotinic acid, 0.5; pyridoxine HCI, 0.1; thiamin * HCl, 0.1; a-naphthaleneacetic acid, 2; kinetin, 0.5; sucrose, 30,000; and Bacto-agar, 10,000. The pH was adjusted to 5.8 (NaOH). A preparation to be tested for cell-division activity was added to this medium with the kinetin omitted, the pH was adjusted to 5.8 with NaOH or HCl, and sterilization was achieved by autoclaving. Each of four 125-ml Erlenmeyer flasks containing 50 ml of hardened medium was planted with four pieces of the stock soybean tissue. After growth for 28 days at 27°C and constant fluorescent lighting at about 40 ft-c, the pieces were weighed individually. The fresh weight averages indicate relative amounts of cell division. Extracts.-Frozen kernels (milk stage) of Zea mays, var. Golden Cross Bantam, were extracted by macerating in either cold or boiling 95 per cent ethanol. The final concentration of ethanol was adjusted to 70 per cent (assuming the weight of kernel was due entirely to water). The extract was cooled and the filtered precipitate discarded. The filtrate was used in all of the experiments. Chromatography.-Ethanol solutions or other preparations were streaked on sheets of Whatman #1 filter paper. For development, one of the following mix-

341 citations

Journal ArticleDOI
01 Sep 1967-Science
TL;DR: Two compounds have been isolated in crystalline form from cultured in liquid media and were found to have properties identical to those of synthetic zeatin andZeatin riboside.
Abstract: The puffball fungus Rhizopogon roseolus produces and releases three cytokinins when it is cultured in liquid media. Two of these compounds have been isolated in crystalline form from such media and were found to have properties identical to those of synthetic zeatin and zeatin riboside.

108 citations

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89 citations

Journal ArticleDOI
TL;DR: Although a number of mycorrhizal species are now known to make and give off cytokinins, an even larger number apparently do not do so under the conditions of screening employed.
Abstract: Several fungi including six species of the genus Rhizopogon, 22 species of Hebeloma and one of Agaricus have been screened for production of cytokinins. The screening was done by culturing cytokinin-requiring soybean callus tissue alongside the fungus on a medium lacking a cytokinin supply. Growth of the soybean callus indicated production of cytokinins by the fungus. Of the fungi tested, only R. ochraceorubens A. H. Smith gave off sufficient cytokinin to be detected. Although a number of mycorrhizal species are now known to make and give off cytokinins, an even larger number apparently do not do so under the conditions of screening employed. An unidentified ectendotrophic species definitely gave off trans-zeatin, which has been crystallized, and probably trans-ribosylzeatin. Suillus punctipes (Pk.) Sing. apparently produced the same two cytokinins.

85 citations


Cited by
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Journal ArticleDOI
TL;DR: Highlights focus on the integration of cytokinin signaling components into regulatory networks in specific contexts, ranging from molecular, cellular, and developmental regulations in the embryo, root apical meristem, stem and root vasculature, and nodule organogenesis to organismal responses underlying immunity, stress tolerance, and senescence.
Abstract: Despite long-standing observations on diverse cytokinin actions, the discovery path to cytokinin signaling mechanisms was tortuous. Unyielding to conventional genetic screens, experimental innovations were paramount in unraveling the core cytokinin signaling circuitry, which employs a large repertoire of genes with overlapping and specific functions. The canonical two-component transcription circuitry involves His kinases that perceive cytokinin and initiate signaling, as well as His-to-Asp phosphorelay proteins that transfer phosphoryl groups to response regulators, transcriptional activators, or repressors. Recent advances have revealed the complex physiological functions of cytokinins, including interactions with auxin and other signal transduction pathways. This review begins by outlining the historical path to cytokinin discovery and then elucidates the diverse cytokinin functions and key signaling components. Highlights focus on the integration of cytokinin signaling components into regulatory networks in specific contexts, ranging from molecular, cellular, and developmental regulations in the embryo, root apical meristem, shoot apical meristem, stem and root vasculature, and nodule organogenesis to organismal responses underlying immunity, stress tolerance, and senescence.

575 citations

Journal ArticleDOI
TL;DR: The preovulatory, preimplantation, and postIMplantation antifertility mechanisms of plant substances affecting the hypothalamus-pituitary, ovary, oviduct, uterus, or vagina are discussed in terms of reproductive differences among laboratory animal species.

407 citations

Journal ArticleDOI
TL;DR: This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology and provides a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products.
Abstract: Fungi are an understudied, biotechnologically valuable group of organisms. Due to the immense range of habitats that fungi inhabit, and the consequent need to compete against a diverse array of other fungi, bacteria, and animals, fungi have developed numerous survival mechanisms. The unique attributes of fungi thus herald great promise for their application in biotechnology and industry. Moreover, fungi can be grown with relative ease, making production at scale viable. The search for fungal biodiversity, and the construction of a living fungi collection, both have incredible economic potential in locating organisms with novel industrial uses that will lead to novel products. This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology. We provide notes and examples for each potential exploitation and give examples from our own work and the work of other notable researchers. We also provide a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products. Fungi have provided the world with penicillin, lovastatin, and other globally significant medicines, and they remain an untapped resource with enormous industrial potential.

404 citations

Journal ArticleDOI
TL;DR: The current understanding of cytokinin metabolism, transport and signaling is summarized, and how this phytohormone regulates changes in gene expression to mediate its pleiotropic effects is discussed.
Abstract: The phytohormone cytokinin plays diverse roles in plant development, influencing many agriculturally important processes, including growth, nutrient responses and the response to biotic and abiotic stresses. Cytokinin levels in plants are regulated by biosynthesis and inactivation pathways. Cytokinins are perceived by membrane-localized histidine-kinase receptors and are transduced through a His-Asp phosphorelay to activate a family of transcription factors in the nucleus. Here, and in the accompanying poster, we summarize the current understanding of cytokinin metabolism, transport and signaling, and discuss how this phytohormone regulates changes in gene expression to mediate its pleiotropic effects.

386 citations