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Cytokinins: Identification of Compounds Isolated from Corynebacterium fascians

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... Many of the symptoms triggered by R. fascians, including abundant shoot proliferation and inhibition of root development, are typical cytokinin effects and addition of cytokinins has been found to mimic some of the symptoms (Thimann and Sachs, 1966;Oduro and Munnecke, 1975;Depuydt et al., 2008). However, despite the detection of several cytokinins in the culture supernatant of R. fascians (Klämbt et al., 1966;Helgeson and Leonard, 1966;Rathbone and Hall, 1972;Scarbrough et al., 1973;Armstrong et al., 1976;Murai et al., 1980;Eason et al., 1996), to date, no clear positive correlation could be made between the amount of secreted cytokinins, the virulence of the producing strain and the kind of cytokinins detected in infected plants. Moreover, contradictory results in planta make it impossible to link cytokinins to symptom development Depuydt et al., 2008;Murai et al., 1980;Balázs and Sziráki, 1974;Eason et al., 1996;Crespi et al., 1992;de O Manes et al., 2001;Galis et al., 2005). ...
... The shooty symptoms that can partially be mimicked by exogenous addition of cytokinins (Thimann and Sachs, 1966;Depuydt et al., 2008), initiated more than 40 years ago experiments to characterize the bacterial cytokinins. Analyses of culture supernatant of different non-isogenic virulent and avirulent R. fascians strains grown under rich culture conditions identified 11 different cytokinins: isopentenyladenine (iP), methylaminopurine (Helgeson and Leonard, 1966), cis-zeatin (cZ) (Scarbrough et al., 1973), 2-methylthio-cis-zeatin (2MeScZ), isopentenyladenosine (iPR) (Armstrong et al., 1976), 2methylthio-isopentenyladenine (2MeSiP), cis-zeatinriboside (cZR), 2-methylthio-ciszeatinriboside (2MeScZR) (Murai et al., 1980), trans-zeatin (tZ), trans-zeatinriboside (tZR), dihydrozeatin (DZ) and dihydrozeatinriboside (DZR) . With the exception of iP, the primary source for these cytokinins was assumed to be tRNA (Murai et al., 1980). ...
... Already since 1966, researchers have wondered which bacterial cytokinins were responsible for the R. fascians-induced phenotype (Thimann andSachs, 1966, Helgeson andLeonard, 1966). The different bacterial isolates had always been grown in relatively rich media, but from recent insights we know that essential virulence genes are not expressed under these conditions Maes et al., 2001). ...
Thesis
The fine-tuned balance of plant regulators plays a key role in growth and development of plants. Many plant-associated bacteria can influence their hosts either by modulating phytohormone production or by producing phytohormones themselves. The Actinomycete Rhodococcus fascians provokes the formation of differentiated leafy galls consisting of numerous shoot primordia that are inhibited in further outgrowth. Based on the shooty phenotype and the presence of an ipt gene on the linear virulence plasmid of R. fascians D188, the role for cytokinins in the pathology had been anticipated for a long time. Subsequent studies identified and characterized the fas operon as a key genetic determinant of virulence and likely cytokinin biosynthesis. Nevertheless, many aspects concerning regulation of fas gene expression, Fas protein function, and, importantly, the encoded cytokinin biosynthetic pathway and the identity of the produced morphogens remained to be uncovered. Therefore, the main objectives of this research were to identify the bacterial cytokinins responsible for the R. fascians pathology, to unravel how they exerted their function, and to elucidate the role of the fas locus and its expression in their production. In conclusion, our data have largely uncovered the role of cytokinins and the fas locus in the R. fascians pathology: the continuous challenge with defined ratios of synergistically acting cytokinins eventually defeats nearly all plants and transforms them into shooty niches. Many intriguing questions derived from the novel insights obtained during this work remain to be answered. Nevertheless, we feel that the results presented here have shed some light on the remaining secrets of this fascinating pathogen.
... These cytokinins have been isolated from cultures of bacteria pathogenic on plants and from plant tumors induced by the bacteria. Agrobacterium tumefaciens produces i6Ade (18), Rhizobium japonicum and R. leguminosarum produce a zeatin-like compound which is zeatin and/or ribosyl-zeatin (7), and Corynebacterium fascians produces cis-zeatin (8) and i6Ade (3). Crown gall tumors resulting from an infection of Agrobacterium produce ribosyl-trans-zeatin (5, 17). ...
... Rhizobium species which produce zeatin or ribosyl-zeatin (7) also induce normal gametophores on P. selwynii and not callus (15). The fact that ciszeatin, i6Ade, and Corynebacterium fascians which produces both cis-zeatin and i6Ade (3,8) all induce callus on P. selwynii may indicate that the cytokinin produced by these bacteria is responsible for the development change on the moss. Experiments by Spiess et al. (16) show that P. selwynii does not respond to A. tumefaciens B6 or to Rhizobium leguminosarum unless the bacteria are in physical contact with the moss. ...
Article
Eight species of mosses studied were divided into two groups on the basis of their developmental responses to ribosyl-trans-zeatin and Agro-bacterium tumefaciens B6. All eight produced either gametophores or callus on the protonema in response to 6-(γ,γ-dimethylallylamino) purine and trans-zeatin. Three which produced normal gametophores with A. tumefaciens yielded callus or abnormal gametophores with ribosyl-trans-zeatin. Ribosyl-trans-zeatin and A. tumefaciens were relatively ineffective on five other mosses. Characteristics of protonemal growth common to each of these two groups are described.
... His material had an ultraviolet spectrum suggestive of a purine and could not be separated from 2iP by paper chromatography. The highly active cytokinin, 6-(3-methyl-2-butenylamino)purine was identified after isolation from culture filtrates of Corynebacterium fascians (12,14), by the same procedures. ...
Article
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Gas-liquid chromatographic retention times for 20 purines or purine nucleosides, 14 of which are highly active cytokinins, are reported. With one exception, all of the naturally occurring cytokinins are separated. Ethyl acetate extraction of yeast transfer RNA hydrolysates and of culture filtrates of Agrobacterium tumefaciens gave sufficient concentration of the naturally occurring cytokinins for immediate gas-liquid chromatography. This procedure permitted the detection of 6-(3-methyl-2-butenylamino)-9-β, d-ribofuranosylpurine in yeast transfer RNA extracts. An active cytokinin was isolated from A. tumefaciens culture filtrates and was tentatively identified as 6-(3-methyl-2-butenylamino)purine.
... Furthermore, the levels of cytokinins are altered in plant tissues infected with Rhodococcus (39,54). Likewise, cytokinins are detectable in Rhodococcus cultures (9,32,34,62,82,103,104). Most importantly, three of the six plasmid-borne fas virulence genes in Rhodococcus encode enzymes involved in synthesizing and modifying cytokinins (34,103,104). ...
Article
Full-text available
Gram-positive bacteria are prominent members of plant-associated microbial communities. Although many are hypothesized to be beneficial, some are causative agents of economically important diseases of crop plants. Because the features of Gram-positive bacteria are fundamentally different relative to those of Gram-negative bacteria, the evolution and ecology as well as the mechanisms used to colonize and infect plants also differ. Here, we discuss recent advances in our understanding of Gram-positive, plant-associated bacteria and provide a framework for future research directions on these important plant symbionts.
... Three crystalline fractions with cytokinin activity as monitored in the tobacco bioassay were obtained (8,10). The most active fraction was identified as 6(3methyl-2-butenylamino)purine (i6Ade) (6), known at that time only as a synthetic, highly active cytokinin (5,9). The second fraction contained nicotinamide. ...
Article
In addition to the four cytokinins, 6-(3-methyl-2-butenylamino)purine, 6-methylaminopurine and the cis and trans isomers of 6-(4-hydroxy-3-methyl-2-butenylamino)purine, reported earlier from our laboratories, three cytokinin-active fractions have been obtained from the aqueous medium of 6-day-old Corynebacterium fascians cultures. One of these has been identified as 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-2-methylthiopurine (2-methylthio-cis-zeatin, c-ms²io⁶ Ade). The elution volumes of the other two fractions correspond to those of authentic 6-(4-hydroxy-3-methyl-2-butenylamino)-9-β-d-ribofuranosyl-purine and 6-(3-methyl-2-butenylamino)-9-β-d-ribofuranosylpurine, indicating the presence of trace amounts of these two ribonucleosides.
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Covering: up to mid-2020 Terpenoids, also called isoprenoids, are the largest and most structurally diverse family of natural products. Found in all domains of life, there are over 80 000 known compounds. The majority of characterized terpenoids, which include some of the most well known, pharmaceutically relevant, and commercially valuable natural products, are produced by plants and fungi. Comparatively, terpenoids of bacterial origin are rare. This is counter-intuitive to the fact that recent microbial genomics revealed that almost all bacteria have the biosynthetic potential to create the C5 building blocks necessary for terpenoid biosynthesis. In this review, we catalogue terpenoids produced by bacteria. We collected 1062 natural products, consisting of both primary and secondary metabolites, and classified them into two major families and 55 distinct subfamilies. To highlight the structural and chemical space of bacterial terpenoids, we discuss their structures, biosynthesis, and biological activities. Although the bacterial terpenome is relatively small, it presents a fascinating dichotomy for future research. Similarities between bacterial and non-bacterial terpenoids and their biosynthetic pathways provides alternative model systems for detailed characterization while the abundance of novel skeletons, biosynthetic pathways, and bioactivies presents new opportunities for drug discovery, genome mining, and enzymology.
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The occurrence of cytokinins in the algae has been the subject of several studies. The main motivation behind this research has been the preoccupation with the utilization and exploitation of the algae as soil conditioners and fertilizers. These hormones have been detected, by bioassay and more recently through the use of high-performance liquid chromatography, in extracts of both unicellular and multicellular forms of the algae. Endogenous applications of cytokinins to algal explants or whole plants indicate that these hormones play a role in algal growth and development, including the processes of cell division and elongation, organogenesis, apical dominance, respiration and photosynthesis.
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The production of N6-(◿2-isopentenyl)adenine in Agrobacterium tumefaciens strain B6 grown in logarithmic phase was estimated to be 0.3 μg/l in the medium and 2.3 μg in the bacteria from 1 l medium. The cytokinin activity of tRNA isolated from the bacteria was estimated to be 10-9 mol cytokinin/mg tRNA after alkaline hydrolysis and 4.6 × 10-10 mol cytokinin/mg tRNA after enzymic hydrolysis. It was calculated that the amount of cytokinin released from tRNA of 2–3 g bacteria present in the medium at early logarithmic phase is sufficient to account for all the cytokinin found. This calculation is based on the estimated half-life of 27.5 hours for tRNA in A. tumefaciens and on the assumption that every tenth macromolecule does contain a cytokinin. The data show that tRNA can be considered as an intermediate in cytokinin biogenesis although the possibility can not be excluded that a second cytokinin biosynthetic pathway independent of tRNA may exist.
Article
To test the hypothesis that the growth inhibition occurring in seedlings of Ardisia species in the absence of their natural bacterial symbionts is due to a lack of cytokinins, we have studied two bacterial strains isolated from two Ardisia species as to a possible production of cytokinins. Extracts of an isolate from Ardisia crenata, of the culture filtrate of this organism, and of the culture filtrate of a Chromobacterium lividum strain that was isolated from A. crispa promoted growth in the soybean callus and the radish cotyledon bioassays for cytokinins. Both organisms caused malformations in pea seedlings exactly like those induced by Corynebacterium fascians. We conclude that the bacterial symbiosis in Ardisia species is based on the fact that the bacteria provide the host plant with cytokinins that it is unable to synthesize itself.
Article
Sixty-nine compounds, mostly purine derivatives and closely related substances, were tested for promotion of growth and regulation of organ formation in the tobacco bioassay to determine relationships between chemical structure and cytokinin activity. Forty-three substances were synthesized in this study, and 13 of these were reported for the first time. N6-Alkyladenines (I) varied in activity over a wide concentration range depending on the length of the alkyl chain. Starting with adenine, detectable at ⩾200 μM, activity increased with the chain length to an optimum for 6-pentylaminopurine detectable at ca. 0–001 μM, and then decreased to reach a barely detectable level for 6-decylaminopurine. The result of the incorporation of polar groups in the side chain was not necessarily reduction in activity. One hydroxyl group, as in zeatin (Id), improved the activity of 6-(γ,γ-dimethylallylamino)purine (Ib) if it affected it at all; two hydroxyl groups, as in 6-(2,3-dihydroxy-3-methylbutylamino)purine strongly reduced activity. Comparisons of 6-isoamylaminopurine with 6-(γ,γ-dimethylallylamino)purine and of other closely related pairs of compounds showed that a double bond in the side chain greatly increased cytokinin activity. Adenine derivatives with cyclic substituents in the N6-position (benzyl-Ic), cyclohexyl-, etc.) showed the same general range of activity, potentiation by unsaturation, and variation in activity with substituent size, etc. as did the alkyl derivatives. Heteroatoms in or on the substituent groups decreased activity (in the case of N or Cl) or had little effect (S for O in furfuryl). Of the mono-substituted adenines only the N6-derivatives definitely possessed cytokinin activity. The 1-(III), 3-(II), or 9-substituted adenines probably are inactive but could be activated by conversion to the N6-isomers. Except for slight activity in tests of high concentrations, which could be ascribed to contaminants, 7-substituted adenines were completely inactive. Modification in the adenine moiety lowered the cytokinin activity, often by 95 per cent or more. Substitution of N for the 8-C atom in kinetin and in 6-benzylaminopurine or S for the 6-amino N atom in 6-(γ,γ-dimethylallylamino)purine did not eliminate but drastically reduced activity in the tobacco bioassay. Elimination of the 6-amino group without substituting another group completely removed activity; thus, the purine derivatives, 1-benzylpurine and 1-(γ,γ-dimethylallyl)purine, were inactive in tests where the 1-adenine derivatives could be activated to give a positive response. Addition of a second substituent on the 1-or 3-position of N6-substituted adenines drastically reduced or eliminated cytokinin activity. It is suggested that the 1-position and possibly also the 3-position must be free. A second substituent in the N6-, 7-, or 9-position of N6-substituted adenine derivatives lowered but did not eliminate activity. Also, the disubstituted 1-adenine derivatives, 1,9-dibenzyladenine and 1,7-dibenzyladenine were active, presumably after rearrangement to the corresponding N6-substituted isomers.
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Three peaks of activity, two of which co-chromatograph with zeatin and zeatin-riboside on Sephadex LH-20, were extracted from wasp larvae found in Erythrina latissima galls. The active substances in the larvae showed a striking similarity to those found in coconut milk.
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This chapter discusses and evaluates the experiments that appear to be promising steps toward explaining the mode of action of cytokinins. Skoog and Armstrong's thorough coverage of structure-activity relationships and the chemistry of cytokinins, both in free form and in tRNA make a detailed presentation of these subjects unnecessary. It summarizes some of the questions that need to be answered before a testable hypothesis of cytokinin action can be proposed. Three general areas require intensive investigation, which are (1) the physiological significance of cytokinins, (2) the site of action of cytokinins, and (3) the primary biochemical reactions that underlie the cytokinin responses. The chapter summarizes the achievements and points out the questions that need to be answered before attempts can be made to propose models for the mode of action of cytokinins.
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Brassica juncea cotyledons were detached from the plant 3 days after inoculation with Albugo candida. Changes in chlorophyll content of infected and noninfected tissue were determined over a 4-day period, during which time distinct "green islands" developed. Following incubation with glycine-2-14C in the light, radioactivity was detected in chlorophylls a and b of both infected and noninfected tissue. Both infected and noninfected tissue fixed 14CO2 in the light during the 4 days after detachment. Most of the incorporated activity was in the 70% ethanol-soluble fraction. At 4 days after detachment, "green islands" fixed 5 times more 14CO2 in the light than noninfected tissue while both types of tissue fixed about the same amount in the dark. Photosynthesis per mole of chlorophyll fell at the same rate in "green island" and noninfected tissue. The maintenance of chlorophyll and continued photosynthetic activity in "green islands" paralleled delayed chloroplast breakdown. "Green island" chloroplasts still had intact grana and relatively small osmiophilic globules 96 h after detachment. In noninfected tissue, grana began to break down and osmiophilic globules increased in size 48 h after detachment. At 96 h after detachment, little grana structure remained and chloroplasts contained greatly enlarged osmiophilic globules interspersed with strands of stroma lamellae. Tissue treated with kinetin responded in essentially the same way as "green island" tissue. Chlorophyll content and photosynthetic capacity were maintained and chloroplast breakdown was delayed.
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Cytokinin nucleotides are normal constituents of transfer RNAs. The formation of free cytokinins might be connected with the normal hydrolysis rate of those RNAs. To get an impression about the cytokinin production by this pathway, the half-life of sRNA from Lactobacillus acidophilus grown in the logarithmic and in the stationary phases has been estimated. At the generation cycle of two hours the half-life of sRNA is 3 to 4 hours during the logarithmic phase, and 10 to 12 hours during the stationary phase.
Article
Der Überstand von D5/23, einem aus der Phyllosphäre von Winterweizen isolierten, assoziativen Rhizosphärenbakterienstamm wurde mittels ELISA und HPLC auf seinen Phytohormongehalt untersucht. Nichthydroxylierte Cytokinine (i6A, i6Ade) wurden im ELISA zu 7,5 ng/ml nachgewiesen. Mittels HPLC konnten zwei Auxinverbindungen (3-Indolylessigsäure, 3-Indolyllaktonsäure) identifiziert werden.
Article
With two extraction procedures differing in the very first extraction steps two cytokinins from a total amount of 180 kg sunflower leaves could be isolated. One of these cytokinins is identified as zeatin by Rf values, UV absorption, melting point of its picrate and its biological activity. The same data are given for the other cytokinin, which is very probably ribosylzeatin. The total free cytokinin content of sunflower leaves is calculated to be 50–90 μg of kinetin equivalent, or 5–9 μg of zeatin, per kg of fresh leaves. Besides the leaf extraction, 100 l of root exudate of sunflowers were collected and the cytokinin was isolated. The root exudate contains 5–6 μg of kinetin equivalent, or 0,5–0,6 μg zeatin per 1 bleeding sap. The Rf values and UV absorption are similar to the corresponding data recorded for zeatin.
Article
A cytokinin was isolated from the culture medium of callus cells of the moss hybridFunaria hygrometrica (L.) Sibth xPhyscomitrium piriforme Brid. The purification procedure included ethyl-acetate extraction, silver-salt precipitation, crystallization as picrate, and ion exchange chromatography. The structure of the cytokinin was confirmed as N(6)-(Δ(2)-isopentenyl)adenine by means of gas chromatography and mass spectrometry. The concentration of the compound in the culture medium was determined at ca. 10(-6) M.
Chapter
Article
Full-text available
This unit describes an effective method for the preparation of natural cytokinins and their synthetic derivatives based on enzymatic cleavage of the N‐glycosidic bond of N6‐substituted adenosine or O6‐substituted inosine derivatives in the presence of purine nucleoside phosphorylase (PNP) and Na2HAsO4. The arsenolysis reaction is irreversible due to the hydrolysis of the resulting α‐D‐ribose‐1‐arsenate. As a result, the desired products are formed in near‐quantitative yields, as indicated by high‐performance liquid chromatography (HPLC) analysis, and can easily be isolated. In the strategy used here, the ribose residue acts as a protective group.
Article
Indole-3-acetic acid (IAA) (Structure 4.1) has been conclusively shown to be a natural hormone, ubiquitously present in higher plants. Evidence is gradually accumulating that there are indolic auxins other than IAA naturally occurring in several plants, i.e., chlorinated derivatives (see Sect. 4.l.1f), or auxin-like compounds which are non-indolic in chemical structure, such as phenylacetic acid (cf. Schneider and Wightman, 1974). The existence of a non-indolic “citrus auxin” (Khalifah et al., 1963), however, is doubtful after repeated re-investigation (Goldschmidt et al., 1971; Takahashi et al., 1975). Research work on steroid-like plant hormones is still in course (Vendrig, 1967 a, b, 1971; Heftmann, 1971, 1975; Kopcewicz, 1971 ; Kopcewicz and Rogozinska, 1972; Geuns, 1974, 1977, 1978 ; Geuns and Vendrig, 1974). This section deals with both IAA as the principal auxin of higher plants and its chlorinated derivatives naturally occurring in the plant. Biosynthesis of IAA in microorganisms is not discussed in detail.
Chapter
Plant growth and differentiation are regulated by growth regulators. Pathogenic infection may cause a departure from normal levels of one or more growth regulators in the infected plant. Imbalance of growth regulation could alter the growth habit of the plant and result in symptoms such as stunting, overgrowth, epinasty, and premature leaf drop.
Chapter
The olefinic gas ethylene (ethene) is the most unusual and perhaps powerful of the growth-regulating chemicals produced by microorganisms and by healthy and diseased plants. The earliest observations of the physiological effects of the gas by Fahnstock (1858) and Girardin (1864, Abeles 1973) were in relation to damage to coleus plants and lime (Tilia vulgaris) trees by fuel (coal) gas contaminated by ethylene. The effects of ethylene on lime trees closely simulated the disease syndrome associated with vascular wilt pathogens such as the Dutch elm disease fungus (Ceratocystis ulmi) on elm, but it was many years later that its biosynthesis by microorganisms (including fungal and bacterial vascular pathogens) was established (Pegg 1976b).
Chapter
Our present understanding of the nature of the molecules that promote cytokinin activity is based on the finding by Miller et al. (1–3) of the growth factor kinetin (1; 6-furfurylaminopurine) in old and heated samples of DNA. The first active analog, 6-benzylaminopurine (2) (4–6), was prepared within days and presaged the synthesis of large numbers of compounds that have helped to define the structure-activity relationships for such species with considerable precision [see, e.g., (7–12)]. Although kinetin is presumably an artifact formed by rearrangement of 2′-deoxyadenosine, structurally related species such as 6-(3-methyl-2-butenylamino)purine (3) were subsequently identified as the growth factors in certain plant pathogens (13–15) and have now been shown to occur more generally in plants at the purine (16–25) and purine ribonucleos(t)ide levels (26 – 28).
Chapter
Gas-liquid chromatography (GLC) of cytokinins was demonstrated by Most et al. (1968) for known compounds and by Upper et al. (1970) for isolation of cytokinins from hydrolysates of t-RNA or extracts of bacterial culture filtrates. Babcock & Morris (1970) demonstrated the feasibility of quantitative as well as qualitative measurements of cytokinin ribosides from t-RNA hydrolysates. The following is a report on our progress in improving separation of known cytokinins, in extending our measurements to include free cytokinins (particularly those from higher plants), and using coupled gas-liquid chromatography-mass spectrometry (GLC-MS). These techniques may provide a simple, sensitive and accurate procedure for identifying and measuring levels of free and t-RNA cytokinins in vivo.
Chapter
It may be expected that an attack on a plant by a pathogen may alter the normal hormonal balance in the plant and in this way change the growth habit of the host. Specific morphogenetic changes of leaves or stems and the production of tumors indicating interference with growth hormone regulation are well known responses (Sequeira, 1963, 1973). Within the context of this book, this Chapter deals primarily with the role of cytokinins in disease symptom expressions. Cytokinins are plant hormones which may be defined as compounds which induce cell division in plant cells in cooperation with an auxin (Skoog et al., 1965; Srivastava, 1967).
Article
The purpose of this chapter is to acquaint the reader with the chemical structures of various plant growth regulators and reports of their detection from plant sources. In general only plant growth substances from higher plants are considered. Growth substances from algae have been recently reviewed by Augier (see Augier, 1978). Kochert (1978) has reviewed sexual pheromones in algae and fungi. This topic will be dealt with in detail also in a forthcoming volume of this Encyclopedia on Interactions Between Plant Cells. Secondary metabolites from bacteria and fungi that affect the growth of higher plants have been reviewed by Strobel (1974, 1977), Patil (1974), Rudolph (1976), Harborne (1977) and Tamura (1979). Letham (1978 b) has reviewed growth substances (other than the principal hormones) from both higher and lower plants.
Chapter
Rhodococcus fascians, causative agent of the leafy gall syndrome, produces a mixture of cytokinins to modify the hormone landscape of its broad range of plant hosts leading to tissue deformations and developmental alterations. Recent developments indicate that the pathogenic nature of these bacteria is superimposed on its plant growth-promoting effect. In the last two decades, its unique position as the only species within the genus able to interact with plants has been overthrown. Indeed, Pistachio Bushy Top Syndrome is an emerging disease linked to the presence of two Rhodococcus species, R. fascians and R. corynebacterioides. Both bacteria would act synergistically to cause the symptoms, giving the prospect of virulence strategies that differ from those of the leafy gall inducers. Additionally, as a result of microbiome research, it is clear that many Rhodococcus species live in close association with plants, and several of them exhibit plant growth-promoting activities. Finally, genome analyses of a collection of R. fascians isolates imply that the taxonomic position of this group of bacteria within the genus will have to be reevaluated, and likely a new genus consisting of several species will be proposed soon.
Chapter
Publisher Summary Alkaloids bearing a purine nucleus form a small but important group of natural products. They are often not classified as alkaloids because of their almost universal distribution in living matter and their mode of biosynthesis which shows no relationship to amino acids from which most alkaloids arise. The chapter explores that some purine alkaloids are major constituents of plants such as tea and coffee which are used throughout the world as stimulating beverages. Many of the physiologically important purine alkaloids possess a xanthine nucleus. Xanthine itself has not been found naturally, but several simple N-alkyl derivatives of xanthine are of considerable significance. Prime among these are 1, 3, 7-trimethyIxanthine (caffeine), 1, 3-dimethylxanthine (theophylline), and 3, 7-dimethylxanthine (theobromine). Other purine alkaloids are derivatives of adenine and guanine, with some of the N 6 -alkylated adenines possessing considerable cytokinin-like activity. The cytokinins are plant growth substances which promote cell division.
Chapter
visible morphological distortions of the plants they infect. Past studies on the effects of these particular pathogen-host interactions have been mainly descriptive and the precise mechanisms which cause these distortion were not well understood. Many of the early efforts have been to examine the diseased plant at the site of infection, and few workers have emphasized the detailed study of the pathogen itself. As stressed previously (Kado, 1976), the rewards will be great when we gain a comprehensive knowledge of the pathogen of interest. This is clearly evidenced by the studies of Agrobacterium tumefaciens, the results of which have yielded a wealth of new information not only in plant pathology, but also in molecular biology and molecular genetics. Furthermore, the discovery that genetic information is naturally transferred from a prokaryote to an eukaryote during the interaction sets a new precedence in biology.
Chapter
Corynebacterium fascians causes fasciation disease or witches’ broom in dicotyledonous plants. The disease is characterized by release of apical dominance and outgrowth of lateral buds, thus giving rise to the characteristic witches’ broom syndrome (Roussaux, 1965). The symptoms of the disease can be duplicated by treatment of seedlings with cytokinins, indicating that the disease may be caused by cytokinins produced by the microbe (Thimann and Sachs, 1966). This work deals with the kinds and quantities of cytokinins released into culture media and present in tRNA of five strains of C. fascians, ranging from highly virulent MW2, moderately virulent Cf2 and Cfl, weakly virulent Cf 15 to avirulent Cfl6. It examines the relationships of the presence of plasmids to cytokinin production and to pathogenicity. It also reports the isolation from highly virulent MW2 of activity of cytokinin synthase that catalyzes the formation of N6-(Δ2-isopentenyl) adenosine-5′-monophosphate (i6 AMP) from 5′-AMP and Δ2-IPP.
Article
The definitive discovery of the cytokinins occurred in 1955 when C. O. Miller, Folke Skoog, M. H. von Saltza, and F. M. Strong, working in the laboratories of Skoog and Strong at the University of Wisconsin, isolated a substance called “kinetin” (6-furfurylaminopurine, C10H9N5O) (Fig. 4-1) from an autoclaved sample of herring sperm DNA and demonstrated it to be very active in promoting mitosis and cell division in tobacco callus tissue in vitro.
Article
Cet article est destiné à définir la nature des substances d'origine bactérienne qui, dans la rhizosphère, sont capables d'intervenir sur la croissance des plantes. Parmi ces substances, les acides aminés et vitamines hydrosolubles, souvent identifiables dans les milieux de cultures bactériennes, ont un rôle difficile à préciser au niveau des plantes et interviennent plutôt sur l'équilibre microbien de la flore rhizosphérique. Par contre, on a pu démontrer que les synthèses bactériennes de substances phytohormonales telles que acide indolyl acétique, gibbérellines et cytckinines agissent directement surla croissance des plantes.
Article
Chemical conversions of 6‐(3‐methyl‐2‐butenylamino)purine, 2iP, and 6‐(3‐methyl‐3‐butenylamino)purine, 3iP, to common products have been effected. A number of compounds related to these isomers and their ribosides have been synthesized, including 6‐(3‐hydroxy‐3‐methylbutylamino)‐9‐β‐D‐ribofuranosylpurine, 6‐(3‐chloro‐3‐methylbutylamino)purine, 6‐(3, 4‐dihydroxy‐3‐methylbutylamino) purine, and 6‐(3,4‐dihydroxy‐3‐methylbutylamino)‐9‐β‐D‐ribofuranosylpurine, and the cytokinin activities have been compared in the tobacco bioassay. The effect of 4‐hydroxyl substitution on the side chain has been noted. Diagnostic fragmentations of the side chains have been observed in the mass spectra.
Chapter
The varied abnormal growths in plants are characterised by extensive alterations and overgrowths due to the plant organ losing control over the growth potential of the affected area. Amongst the different types of abnormal growth, galls, hypertrophies, malformations and witches-brooms are worth mention. The various agents or conditions reported to act as incitants of abnormal growth in plants are: physical and chemical agents, genetic constitution, bacteria, viruses, fungi, insects, mites and nematodes. The abnormal growths are unique examples of complex interactions and mutual adaptation between the host and the pathogen. As a result of an attack on a plant by a pathogen the normal growth hormone balance is disturbed which brings about the change in the growth habit of the host. Within the context of this volume the text will be confined to a consideration of some of the important abnormal growths in plants and their hormonal regulation.
Article
A review is given on biochemical aspects of stress physiology and defense mechanisms of plants with special reference to coniferous trees. To date, investigations on these topics have proceeded on a wide front. These include biotic (fungi, bacteria, parasitic higher plants, nematodes) and abiotic (temperature, moisture, light, pH, host-plant nutrition) stress phenomena as well as their causal relationships to biochemical and histological defense mechanisms. Research dealing with hormonal control of defense mechanisms is emphasized in this review.
Article
High concentrations of kinetin (400–2,000 μg/l) permit continuous growth of tobacco callus cultures (Nicotiana tabacum, var. Wisconsin No. 38) in the absence of exogenous thiamine. On the optimum concentration (1,000 μg/l) the tissue has been maintained through 21 bimonthly passages without change in vigor or other growth characteristics. The effect of kinetin is general, not “mutagenic”, because tissue returned to low-kinetin, thiamine-free medium failed to grow. Kinetin-thiamine interactions in “cytokinin mutant” strains which were grown without cytokinin in light and darkness suggest that the endogenous content of cytokinins may markedly affect the requirement for thiamine and possibly the tissue content of this vitamin and other growth factors. The viability of tissue on low-kinetin media in enhanced by thiamine, but the addition of this vitamin does not eliminate the requirement for a cytokinin. The great divergence in minimum kinetin concentrations required for growth of the tissue in the presence and absence of thiamine indicates that the growth promoting action of cytokinin must be different in the two cases.
Article
Cytokinin activity has been obtained in ethanol extracts of Begonia and Bryophyllum plants. Begonia x cheimantha Everett yielded 30 to 300 μg kinetin equivalents per kg of fresh leaves in the tobacco callus bioassay. Short day conditions appeared to increase the extractable cytokinin content in the tissue.Purification by fractionation on Dowex 50 H+ columns followed by organic solvent extraction, silver precipitation, and repeated paper chromatography yielded an apparently homogeneous product which accounted for most of the activity in the Begonia extracts. It was indistinguishable from zeatin in chromatograms developed with six solvent systems.Other cytokinin active fractions were also obtained from both Begonia and Bryophyllum. Crystalline picrate preparations of active products were insufficient for identification by mass spectrometry.
Article
The compound previously described as 6-dimethylamino-"7"-methylpurine obtained by a direct methylation procedure has now been shown to be dimethylamino-3-methylpurine (III) by unambiguous, independent syntheses of both compounds. This finding necessitated a reinvestigation of several purine nucleosides related to puromycin, the structure of which had been assigned previously by comparison with 6-dimethylamino-"7"-methylpurine on the basis of ultraviolet absorption spectra. By providing sets of comparably substituted adenines, it has been possible for us to develop further the spectral methods for differentiation between adenine derivatives substituted at various nitrogen atoms. With the utilization of the ultraviolet absorption data supplemented by proton magnetic resonance spectra, the structures of a number of previously described 6-dimethylamino-"7"-glycosylpurines have now been reassigned as the corresponding 3-glycosyl derivatives. Thus, conversion of a purine to its mercuric salt does not necessarily direct glycosidation exclusively to the imidazole ring.
Article
Evidence from chemical degradations and physical methods has indicated that the structure of triacanthine is 6-amino-3-(γ,γ-dimethylallyl)-purine (V). Use of the "exchange animation" reaction has been introduced in the structure proof, and the acid cleavage of substituted N-allylic adenines has been documented. A combination of ultraviolet spectral and dissociation constant data has now provided a general method for distinguishing between 3-, 7- and 9-substituted adenines. Triacanthine and several of its isomers have been synthesized by alkylation of adenine, the alkylation on N3 representing an unusual departure from the hitherto expected course of purine alkylations. Ozonolysis studies of substituted N-allylic adenines have revealed a new feature potentially important when this degradation of hemiterpenic side chains is used as a means of structure proof. Finally, the formation of pyrotriacanthine chloride (XXV) provides a starting point for the study of allylic ring closures and rearrangements on the purine nucleus.
Article
Enzymes put finishing touches characteristic of each species on RNA and DNA by insertion of methyl groups.
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24 Witham, F. H., and C. 0. Miller, Physiol. Plantarum, 18, 1007 (1965).
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18 See Hall, R. H., Biochemistry, 4, 661 (1965), and Srinivasan, P. R., and E. Borek, Science, 145, 548 (1964) for references to the isolation of "minor" bases from nucleic acid hydrolysates. 19 Strong, F. M., Topics in Microbial Chemistry (New York: John Wiley and Sons, Inc., 1958), pp. 98-157.
Lecture at Fairleigh-Dickenson University
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26 Leonard, N. J., Lecture at Fairleigh-Dickenson University, Madison, N. J., Oct. 21, 1963; see Transactions of Morris County Research Council, 1, 11-41 (1965).
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Skoog, F., F. M. Strong, and C. 0. Miller, Science, 148, 532 (1965).
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9 Letham, D. S., J. S. Shannon, and I. R. McDonald, Proc. Chem. Soc., 230 (1964).
11 Cav6, A., Doctor of Natural Sciences thesis
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10 Shaw, G., and D. V. Wilson, Proc. Chem. Soc., 231 (1964). 11 Cav6, A., Doctor of Natural Sciences thesis, University of Paris, 1962. 12 Leonard, N. J., and T. Fujii, these PROCEEDINGs, 51, 73 (1964).