Showing papers on "Zeatin published in 2001"
TL;DR: The discovery of a cis-zeatin-specific O-glucosyltransferase isolated from maize indicates the existence of cis-specific regulatory elements in plants and suggests that cis-ZEatin and derivatives may be more important in cytokinin homeostasis than currently recognized.
Abstract: Zeatin is a naturally occurring cytokinin. Biosynthesis and metabolism studies of zeatin have been directed mostly at the trans isomer, although cis-zeatin and its riboside occur as major components in some plant species. It is not known whether parallel regulatory pathways exist for the two isomers. Based on the sequence of the gene ZOG1 encoding a trans-zeatin O-glucosyltransferase from Phaseolus (EC 2.4.1.203), a cis-zeatin-specific O-glucosyltransferase was isolated from maize. This gene, cisZOG1, contains an ORF of 1,401 nucleotides encoding a protein of 51.1 kDa with 41% identity to the Phaseolus ZOG1 protein. Unexpectedly, the maize enzyme recognizes as substrates cis-zeatin and UDP-glucose but not cis-ribosylzeatin, trans-zeatin, or trans-ribosylzeatin. This finding indicates the existence of cis-specific regulatory elements in plants and suggests that cis-zeatin and derivatives may be more important in cytokinin homeostasis than currently recognized.
134 citations
TL;DR: Embryo formation on leaf explants was retarded by all four auxins tested, but promoted by all the cytokinins, and the highest average number of embryos per explant (10.7) was found on a basal medium containing 1 mg/l TDZ.
Abstract: Four auxins (IAA, IBA, NAA and 2,4-D) and five cytokinins (2iP, zeatin,kinetin,BA and TDZ) were examined for their effects on direct somatic embryogenesis onleaf explantsof a sympodial orchid Oncidium 'Gower Ramsey’.On a hormone-freebasal medium, the percentages of embryo formation were 40%, 20%,5% and0% on leaf tips, adaxial sides, wound surfaces and abaxial sides of theleaf explants, respectively, and the average number of embryos per explant was5.6. Embryo formation on leaf explants was retarded by all four auxins tested,but promoted by all the cytokinins. The percentages of embryo formation werereduced to 20%, 5–10%, 0% and 0%,respectively, in the same parts of leaf explants when supplemented with lowdogsages of IAA (0.3–3 mg/l) on the basal medium.Furthermore, embryo formation was totally inhibited by 3 mg/l NAA,0.3–3 mg/l IBA and 2,4-D. The sequence of embryo formationonvarious location of leaf explants was altered by 0.3–1 mg/l2iP and 3 mg/l zeatin, and embryo formation on adaxial sides> leaf tips > woundsurfaces > abaxial sides. The highest percentage of embryoformation on leaf tips, adaxial sides and wound surfaces of explants were75%, 50% and 20% when supplemented with 1mg/lTDZ, 1 mg/l 2iP and 0.3 mg/l kinetin, respectively.The highest average number of embryo per explant (10.7) was found on a basalmedium containing 1 mg/l TDZ.
105 citations
TL;DR: Higher levels of free IAA and ABA were obtained in the embryogenic calli when compared to the non-embryogenic, while no differences were observed among callus types in the other hormones evaluated.
Abstract: Carrot (Daucus carota L. F1 hybrid Starca) excised hypocotyls were cultured on Murashige and Skoog medium with and without 2,4-dichlorophenoxy acetic acid (2,4-D) to determine the effect of this plant growth regulator on their further development and their endogenous hormone levels. Culture in the absence of 2,4-D stimulated root development at one end of the hypocotyl segments and increased the endogenous levels of free indole-3-acetic acid (IAA), zeatin/zeatin riboside and N6(Delta2-isopentenyl) adenine/N6(Delta2-isopentenyl) adenosine, as determined by radio-immunoassay. On the other hand, the presence of 2,4-D in the culture medium promoted callus induction and proliferation, together with abscisic acid (ABA) accumulation, in the hypocotyl segments during the first weeks of culture. When the callus segments generated in the hypocotyl sections cultured in the presence of 2,4-D were cultivated further, the development of two callus types was observed, one composed of preglobular and globular embryos and the other translucent, watery and lacking any sign of organisation. The embryos of the first type germinated when callus segments were transferred to regeneration conditions, while no change was observed when the second type was induced to regenerate. Higher levels of free IAA and ABA were obtained in the embryogenic calli when compared to the non-embryogenic, while no differences were observed among callus types in the other hormones evaluated. The possible role of the different plant hormones during induction of somatic embryogenesis is discussed.
87 citations
TL;DR: The identities and concentrations of cytokinins in goldenrod ball galls, normal goldenrod stems, and in the gall-forming larvae of the tephritid fly Eurosta solidaginis were determined in order to gain insight into the mechanism of ball gall formation on Solidago altissima.
Abstract: ummary
• The identities and concentrations of cytokinins in goldenrod ball galls, normal goldenrod stems, and in the gall-forming larvae of the tephritid fly Eurosta solidaginis were determined in order to gain insight into the mechanism of ball gall formation on Solidago altissima.
• Zeatin, zeatin riboside, isopentenyladenine, and isopentenyladenosine were identified and quantified by gas chromatography–mass spectrometry in ball galls, goldenrod stems, and in larvae of E. solidaginis.
• Concentrations of the four cytokinins were higher in gall tissues than in stem tissues when expressed on a weight per stem length basis but not when expressed on a weight per weight basis. Isopentenyladenine was the most abundant cytokinin in larvae from developing galls and in larvae from fully formed galls exhibiting ‘green islands’. In first instar larvae, isopentenyladenine was present at a much higher concentration (c. 50 fold) than in control stem tissues.
• The presence of an E. solidaginis larva results in higher cytokinin amounts in a given length of stem than are found in its absence. Larvae of E. solidaginis may act as point sources of isopentenyladenine in developing ball galls.
Abbreviations
BHT, butylated hydroxytoluene; DMSO, dimethylsulphoxide; DMSO−, dimethylsulphoxide anion; GC-MS, gas chromatography mass spectrometry; HPLC, high pressure liquid chromatography; iP, isopentenyladenine; iPA, isopentenyladenosine; Me-dHZ, methyl-dihydrozeatin; Me-dHZR, methyl-dihydrozeatin riboside; Me-iP, methyl-isopentenyladenine; Me-iPA, methyl-isopentenyladenosine; Me-Z, methyl-zeatin; Me-ZOG, methyl-zeatin-O-glucoside; Me-ZR, methyl-zeatin riboside; Me-ZROG, methyl-zeatin riboside-O-glucoside; m/z, mass to charge ratio; PVPP, polyvinylpolypyrrolidone; SIM, selected ion monitoring; TEAB, triethylammonium bicarbonate; Z, zeatin; ZR, zeatin riboside.
81 citations
TL;DR: Although it had the lowest percentage of elongated shoots, medium containing thidiazuron alone performed better than all other growth regulators tested, with the highest percentage of shoot induction and the largest number of shoots, particularly at a concentration of 2.5 μM.
Abstract: Sugarcane (Saccharum spp. hybrid cv. CP 84-1198) embryogenic calluses were induced from young leaves cultured on modified Murashige and Skoog basal medium supplemented with 13.6 μM 2,4-dichlorophenoxyacetic acid. Five concentrations, 0.5, 1.0, 2.5, 5.0, and 10.0 μM, of five different growth regulators, 6-benzylaminopurine, kinetin, 6-γ,γ-(dimethylallylamino)purine, zeatin, and thidiazuron, were tested with or without 22.5 μM α-naphthaleneacetic acid to compare their ability to induce regeneration from embryogenic callus. After 4 wk on medium, the percentage of shoot meristem induction was evaluated, and after 10 wk the total number of shoots produced, as well as the percentage of shoots greater than 1 cm in length, was obtained. Although it had the lowest percentage of elongated shoots, medium containing thidiazuron alone performed better than all other growth regulators tested, with the highest percentage of shoot induction and the largest number of shoots, particularly at a concentration of 2.5 μM.
77 citations
TL;DR: When analysing the endogenous hormone levels in the various callus types generated in each genotype, it was found that only differences in the IAA levels accounted for variations in the morphogenic properties of the calli.
75 citations
TL;DR: When analysing the endogenous hormone concentrations in the various callus types generated in each genotype, it was found that only differences in the free IAA concentrations were associated with variations in the morphogenic properties of the calluses.
Abstract: Immature zygotic embryos of two wheat (Triticum aestivum L.) genotypes, known for their different ability to generate embryogenic callus, were used as initial explants to establish callus cultures. Embryogenic and non-embryogenic calluses were obtained from the competent genotype (`Combi'), while only non-embryogenic callus was produced by the incompetent one (`Devon'). The morphogenetic competence of each callus type was evaluated by transferring some segments to regeneration conditions. The endogenous hormone concentrations (free indole-3-acetic acid [IAA], abscisic acid [ABA], gibberellins 1, 3 and 20 [GAs], zeatin/zeatin riboside [Z/ZR] and N6[Δ2-isopentenyl] adenine/ N6[Δ2-isopentenyl] adenosine; [iP/iPA]) of the initial explants were determined by means of radio-immunoassay and showed that the only difference was the higher concentration of ABA found in the embryos of the most competent genotype; whose embryos showed a reduced rate of precocious germination. When analysing the endogenous hormone concentrations in the various callus types generated in each genotype, it was found that only differences in the free IAA concentrations were associated with variations in the morphogenic properties of the calluses. Higher concentrations of endogenous free IAA were typical of embryogenic callus cultures. It was also observed that a loss in the embryogenic competence of the calluses, due to a prolonged time of culture, occurred concomitantly with a reduction in free IAA concentrations, practically to the concentrations found in the non-embryogenic calluses.
71 citations
06 Jul 2001
TL;DR: With all three cultivars, a reasonable balance in terms of shoot multiplication rate and desirable growth characteristics was attained in a new medium and the new protocol proposed from this study is expected to be adapted for propagating a wide range of lingonberry germplasm.
Abstract: Shoots of three lingonberry (Vaccinium vitis-idaea L.) cultivars, ‘Regal’, ‘Splendor’, and ‘Erntedank’ and two clones from natural stands in Newfoundland were initiated in vitro from shoot tip and nodal explants on modified Murashige and Skoog (MS) medium containing the plant growth regulators N6-[2-isopentenyl]adenine (2iP) (12.3 μM) or zeatin (5.7 μM). Zeatin was more effective than 2iP, and induced proliferation of 2 to 3 times as many shoots in ‘Regal’ as 2iP. Out of four media tested for shoot proliferation, modified MS medium was found more effective than the Woody Plant Medium for shoot multiplication. With all three cultivars, a reasonable balance in terms of shoot multiplication rate and desirable growth characteristics was attained in a new medium. Nodal explants of the two clones cultured on the modified MS medium with 12.3 μM 2iP produced 4 to 6 healthy axillary shoots per explant in clone 1 and 2 to 4 shoots in clone 2. Shoots rooted well ex vitro directly on a 2 peat: 1 perlite (v/v...
69 citations
TL;DR: An efficient procedure has been developed for inducing somatic embryogenesis from leaf cultures of potato cv.
Abstract: An efficient procedure has been developed for inducing somatic embryogenesis from leaf cultures of potato cv. Jyothi. Leaf sections were initially cultured on 2,4-dichlorophenoxyacetic acid (2,4-D) + benzyladenine (BA) and α-naphthaleneacetic acid (NAA) + BA supplemented Murashige and Skoog (MS) media. Nodular embryogenic callus developed from the cut ends of explants on media containing 2,4-D and BA, whereas compact callus developed on media containing NAA and BA. The explants with primary callus were subsequently moved onto MS media containing zeatin and/or gibberellic acid (GA3) and BA. Treatment with zeatin (22.8 μM) and BA (10.0 μM) resulted in the induction of the highest number of somatic embryos directly from meristematic centres produced on the nodular tissue. Embryo induction and maturation took place on this medium. The cotyledonary stage embryos developed into complete plantlets on hormone-free MS medium. A distinct feature of this study is the induction of somatic embryogenesis in leaf cultures of potato which has not been reported previously.
66 citations
TL;DR: Embryo regeneration was studied by transferring the callus from EIM to embryogenesis expression medium (EEM) containing different concentrations of 2-isopentenyladenine (2iP), BA, thiadiazuron (TDZ), zeatin or kinetin, and 2iP at 10.0 μM outperformed the other growth regulators.
54 citations
TL;DR: The profile of various hormones was assessed during maturation of somatic embryos of hybrid larch and plant growth regulators were extracted in methanol, purified, fractionated by high pressure liquid chromatography (HPLC) and quantified by enzyme-linked immunosorbent assay (ELISA).
TL;DR: The number of plants regenerated per explant was improved over previous procedures, with means of 34 plants per scutellum, and 16 plants per inflorescence explant, and the addition of 1 mg/l 6-BAP to the plantlet growth medium was found to enhance tiller production in regenerants.
Abstract: Scutellum and inflorescence explants of four genotypes of durum wheat(Triticum turgidum var. durum Desf.) were used to define culture conditions to obtain high frequencies of embryogenesis and plant regeneration in vitro. Under all conditions tested, scutellum cultures gave higher frequencies of embryogenesis and plant regeneration than inflorescence cultures. Two different auxins, 2,4-D(2,4-dichlorophenoxyacetic acid) and picloram(4-amino-3,5,6-trichloropicolinic acid), were compared for their effect on scutellum and inflorescence explant response in vitro. Picloram was found to significantly increase the frequency of plant regeneration from both explants. When cultures were grown on regeneration medium containing zeatin for two three-week passages, the frequency of plant regeneration increased by between 20–30% compared with cultures exposed to hormones for a single three-week passage. Finally, the addition of 1 mg/l 6-BAP (6-benzyl aminopurine) to the plantlet growth medium was found to enhance tiller production in regenerants. The optimized culture conditions were applicable to the four genotypes tested and frequencies of plant regeneration varied between 97% to 100% for scutellum cultures (2 mg/l picloram in induction medium) and between45% and 80% for inflorescence cultures (4 mg/l picloram in induction medium). The number of plants regenerated per explant was improved over previous procedures, with means of 34 plants per scutellum, and 16 plants per inflorescence explant.
TL;DR: The results suggested the combination of two factors, changes in the endogenous hormonal content in original explants and loss of their sensitivity to exogenously applied BA, as the cause for the reduction of the ability of Pinus pinea cotyledons to form adventitious buds.
TL;DR: Somatic embryos (SEs) formed on in vitro-cultured stem internodes, leaves, microtubers and roots of 18 tetraploid potato cultivars, diploid and monoploid germplasm and three wild Solanum species to produce thin-stemmed plantlets resembling potato seedlings.
Abstract: Somatic embryos (SEs) formed on in vitro-cultured stem internodes, leaves, microtubers and roots of 18 tetraploid potato (Solanum tuberosum L.) cultivars, diploid and monoploid germplasm and three wild Solanum species. A two-step protocol with 6-benzylaminopurine or thidiazuron in the first medium, and zeatin, indoleacetic acid and gibberellic acid in the second medium produced SEs within 14–28 days. SEs developed through the globular, heart and torpedo stages to produce thin-stemmed plantlets resembling potato seedlings. Plantlets transferred to the greenhouse produced greenhouse tubers. Secondary SEs were observed at the base of germinating torpedo-stage SEs in culture. SEs formed on stem internode sections, leaves and microtuber slices of in vitro-grown plants. Genotypic differences in regenerative capacity were clearly evident.
TL;DR: It is hypothesised that cell division initiated by a relatively high endogenous level of cytokinins just after cutting the slices is a necessary, initial step in adventitious root formation.
Abstract: We examined the role of cytokinins in rooting of 1-mm stem slices cut from microcuttings of the apple rootstock ‘Jork 9˚s. Various types of cytokinins inhibited the rooting of apple stem slices to different extents. Highest inhibition was obtained with thidiazuron and benzylaminopurine. Remarkably, isopentenyladenine and isopentenyladenosine enhanced rooting at low concentration (at the optimal concentration of 0.1 μM by 53 and 19%, respectively). We also examined the effect of lovastatin and simvastatin. These drugs are putative cytokinin-synthesis inhibitors. Both inhibited rooting and inhibition was partially reversed by simultaneous addition of zeatin. Moreover, in the presence of lovastatin a higher concentration of zeatin had to be applied to achieve inhibition of rooting than in the absence of the drug. This data indicates that these compounds indeed inhibited cytokinin synthesis. One-day pulses with lovastatin strongly blocked rooting when given just after cutting the slices but had no ef...
TL;DR: At specific stages during floret development, solutions of IAA,GA3, zeatin and ABA were injected into the leaf sheath around spike of wheat to study the regulating effects of exogenous hormones on florets.
Abstract: At specific stages during floret development, solutions of IAA,GA3, zeatin and ABA were injected into the leaf sheath around theyoung spike of wheat (Triticum aestivum L.) to study theregulating effects of exogenous hormones on floret development. Zeatin promotedfloret development and significantly increased the number of fertile florets aswell as grain set, especially at the stage of anther-lobe formation. Zeatinalsoincreased the sugar concentrations in spikes at anthesis. In contrast, IAA,GA3 and ABA inhibited floret development, with different patternsforeach of the hormones. IAA inhibited the development of the whole spike and allflorets in the spikelets such that grain loss occurred in all positions in thespikelets. GA3 increased the number of fertile florets per spike,butdecreased grain set of the third floret in each spikelet, especially whenapplied at terminal spikelet formation. ABA inhibited floret development, anddecreased the number of fertile florets and grain set at almost all developmentstages, except at anther-lobe formation. The inhibitory effect of ABA wasmainlyon the first and third florets in each spikelet.
TL;DR: Increased zeatin O-glucosylation in detached, cytokinin-dependent tissues leads to a shift in the response to exogenous zeatIn indicative of cytokinIn sequestering, the effect can simulate a reduction or a rise in cytokin in activity depending on the tissue and stage of development.
Abstract: Zeatin and its derivatives are major consituents of higher plant cytokinins. Metabolic steps modifying the isoprenoid side chain, such as O-glycosylation, are expected to have a direct bearing on cytokinin-mediated processes. To examine this possibility, transgenic tobacco plants were generated harboring a gene (ZOG1) encoding a zeatin O-glucosyltransferase from Phaseolus lunatus under the control of a constitutive (35S) and an inducible (Tet) promoter. The presence of the transgene resulted in elevated enzyme production and conversion of exogenous zeatin to its O-glucoside, confirming the expression of the ZOG1 gene in transgenic plants. Endogenous O-glucosylzeatin was increased from less than 1 pmol per g fresh weight in leaves and roots of controls to 26 and 68 pmol per g fresh weight in leaves and roots of 35S-ZOG1 transformants, respectively. In cytokinin/auxin interaction experiments, Tet-ZOG1 leaf discs, in the presence of tetracycline, required 10-fold higher zeatin concentrations for the formation of shoots and callus than the controls. In 35S-ZOG1 plants, developmental changes included adventitious root formation on the lower stems, shorter stature, and axillary shoot growth. Thus, increased zeatin O-glucosylation in detached, cytokinin-dependent tissues leads to a shift in the response to exogenous zeatin indicative of cytokinin sequestering. In whole plants the effect can simulate a reduction or a rise in cytokinin activity depending on the tissue and stage of development. The use of tissue- and stagespecific promoters in the future will allow more precise analyses and targeted growth alterations.
TL;DR: Results suggest that changes in cytokinin efficacy in dormant potato tubers during postharvest storage are not the result of differential catabolism butrather are due to other cellular processes such as hormone perception and/ororsignal transduction.
Abstract: The metabolism of [3H]-zeatin (Z) and[3H]-isopentenyladenosine (IPA) in potato tubers was examined inrelation to changes in cytokinin efficacy during postharvest storage anddormancy progression. Exogenous radiolabeled cytokinins were rapidlymetabolizedby dormant and nondormant tubers. Following injection, [3H]-Z wasmetabolized to zeatin riboside, adenine derivatives andzeatin-riboside-5′-monophosphate. Four hours after injection, less than60% of the recovered radioactivity was associated with unmetabolized[3H]-Z. [3H]-IPA was also rapidly metabolized to severalmetabolites including: IPA-5′-monophosphate, adenine derivatives andzeatin riboside. Four hours after injection, less than 50% of therecovered radioactivity was associated with [3H]-IPA. Cytokininsensitivity was assessed by determining the effects of exogenous Z or IPA ontuber sprouting. Immediately after harvest and during the initial period ofstorage, tubers were dormant and exogenous Z or IPA were completely ineffectivein breaking tuber dormancy. Thereafter, dormant tubers exhibited a gradualincrease in sensitivity to both cytokinins. Cytokinin sensitivity continued toincrease as postharvest storage was extended and dormancy weakened. The lengthof postharvest storage (hence dormancy status) had no apparent effects on themetabolism of either cytokinin. Neither the rate of metabolism nor the natureofmetabolites detected was affected by the length of postharvest storage. Theseresults suggest that changes in cytokinin efficacy in dormant potato tubersduring postharvest storage are not the result of differential catabolism butrather are due to other cellular processes such as hormone perception and/orsignal transduction.
TL;DR: Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were investigated in the Mediterranean shrubs rosemary and lavender, finding that chlorophyll and carotenoid concentrations fell significantly in water-stressed lavender leaves.
Abstract: Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were investigated in the Mediterranean shrubs rosemary (Rosmarinus officinalis L.) and lavender (Lavandula stoechas L.). Two-year-old, greenhouse-grown plants were placed in a whole-shoot gas-exchange measurement system and subjected to 10 days of drought, resulting in severe water stress, and then re-watered for 5 days in order to study their recovery. Water stress resulted in a significant decline in maximum whole-shoot net CO2 assimilation rates (An) for both species that was associated with reductions in leaf area and stomatal conductance. Because shoot dark respiration rate (Rd) was less sensitive to water stress than An, shoot Rd/An ratio increased from about 15 to 95% during water stress. No major changes in chlorophyll and carotenoid concentrations of rosemary leaves were observed during the experiments, but chlorophyll and carotenoid concentrations fell significantly in water-stressed lavender leaves. Zeatin concentrations were higher in rosemary leaves than in lavender leaves during water stress. After re-watering, whole-shoot An and Rd rapidly recovered to their pre-drought rates.
TL;DR: The increases of cytokinin induced by these chemicals may be caused via the depletion of the auxin level and/or the activity in shoot tissues and may be involved in the increase of flower bud production on the Japanese pear shoot.
TL;DR: In this work a propagation system was devised where the addition of growth regulators was restricted to the induction phase therefore reducing the risks of epigenetic and somaclonal variation.
Abstract: A simple and reliable method was established for the maintenance of a permanent stock of several Medicago truncatula genotypes selected from a general seed stock by their in vitro culture amenability and embryogenic capacity. In the first step, multiple shoots were induced from the cotyledon axillary meristem meristem of pre-germinated seeds in Murashige and Skoog medium supplemented with cytokinins (9.3 μM zeatin, 22.2 μM benzylaminopurine or 4.5 μM thidiazuron). In the second step, the induced shoots were allowed to develop in growth-regulator-free medium. Benzylaminopurine at 22.2 μM supported the best combination of shoot quality and number of shoots produced. Rooting of microshoots depended on the cytokinin used for shoot induction and was faster for zeatin-treated shoots. In this work a propagation system was devised where the addition of growth regulators was restricted to the induction phase therefore reducing the risks of epigenetic and somaclonal variation.
TL;DR: The protoplast-derived plants showed some alterations in morphological characteristics from those of the in-vitro-germinated control plants.
TL;DR: In treated plants, zeatin concentrations in the leaves of L. esculentum decreased within 24-72 h after treatment, and ABA levels in treated plants of both species increased significantly compared to the controls.
Abstract: Indoleacetic acid (IAA), gibberellic acid (GA3), zeatin, and abscisic acid (ABA) levels in cultivated tomato Lycopersicon esculentum (Mill.) cultivar Falcon 82 and its wild salt-tolerant relative L. pennellii (Correll) were examined over a range of 0 to 150 mM NaCl applied for 72 h. The treatment with 50 mM and 150 mM NaCl reduced relative water and protein contents in L. esculentum, but did not affect relative water content and increased protein content in L pennellii. Varietal differences between L. esculentum and L. pennellii were also observed in hormonal contents during the stress period. ABA levels in treated plants of both species increased significantly compared to the controls. However, the increase in the leaves of L. pennellii due to NaCl stress was not as pronounced as that of L. esculentum; it was significantly higher (p < 0.05) than that of salt-sensitive L. esculentum. In treated plants, zeatin concentrations in the leaves of L. esculentum decreased within 24-72 h after treatment. Neverthel...
TL;DR: An efficient and simple plant regeneration system via organogenesis from leaf segments of persimmon cultivars ‘Fuyu’ and ‘Nishimurawase’ has been developed and dark incubation was the most effective condition to successfully influence shoot regeneration in both cultivars.
Abstract: An efficient and simple plant regeneration system via organogenesis from leaf segments of persimmon (Diospyros kaki Thunb.) cultivars ‘Fuyu’ and ‘Nishimurawase’ has been developed. The regeneration capacity was influenced by the culture vessels, gelling agents, plant growth regulators, and light conditions. Leaf explants taken from in vitro shoots were cultured on a modified Murashige and Skoog medium (MS1/2N), for 16 wk without transfer to fresh medium. Adventious shoots appeared after 4 and 8 wk in culture of ‘Nishimurawase’ and ‘Fuyu’ tissues, respectively. The culture of leaf explants in Erlenmeyer flasks with medium containing 4 g l−1 agar enhanced shoot formation in comparison to media with increased agar concentrations. Optimal shoot regeneration was obtained with 5 mg l−1 (22.8 μM) zeatin and 0.1 mg l−1 (0.05 μM) indole-3-butyric acid (IBA) for ‘Nishimurawase’, and 10 mg l−1 (45.6 μM) zeatin and 0.1 mg l−1 (0.05 μM) IBA for ‘Fuyn’. Shoot regeneration frequencies in both cultivars were 100%, and shoot numbers per explant reached up to 9.2 for ‘Nishimurawase’ and 2.2 for ‘Fuyu’. Dark incubation during the first 4–5 wk was the most effective condition to successfully influence shoot regeneration in both cultivars. While dark incubation was essential for adventitious shoot formation by ‘Fuyu’, it was only slightly beneficial to ‘Nishimurawase’. More than 80% of the regenerated shoots rooted within 4 wk on hormone-free MS1/2N demium after having been dipped for 30 s in 250 mg l−1 (1.1. mM) IBA solution.
Journal Article•
TL;DR: DNA and RNA hybridization analyses showed that the introduced gene was integrated and stably expressed in regenerated plants and the in vitro condition of the plant regeneration has been optimized.
Abstract: Two transgenic pepper plants were obtained from 255 seed explants that were infected with Agrobacterium LBA4404 (pGA1209). One of them (PT2) showed morphological change, such as dwarfism and early flowering by the constitutive expression of the rice OsMADS1 gene. The in vitro condition of the plant regeneration has been optimized from hypocotyl explants on a MS medium that was supplemented with zeatin 3 mg/L, IAA 0.3 mg/L for shoot induction. The optimal rooting condition was at NAA 0.3 mg/L. The transformation frequency was 0.8% from the total hypocotyls. DNA and RNA hybridization analyses showed that the introduced gene was integrated and stably expressed in regenerated plants.
TL;DR: Two independent transformants of sugarbeet exhibited a number of distinguishable morphological alterations commonly induced by cytokinins, i.e. less root growth, reduced leaf surface area, and increased axillary shoot development.
Abstract: Expression of a bacterial cytokinin biosynthesis gene fused to a patatin gene promoter was studied in sugarbeet (Beta vulgaris L.). Two independent transformants, Pat-ipt 1 and 2, exhibited a number of distinguishable morphological alterations commonly induced by cytokinins, i.e. less root growth, reduced leaf surface area, and increased axillary shoot development. Concentrations of the cytokinins zeatin and zeatin riboside were increased by twofold in taproots and 7- to 18-fold in leaves. Leaf sucrose and glucose concentrations were not significantly different from those in control plants except in Pat-ipt 2 where glucose levels were elevated ninefold. Since normal taproot development was severely inhibited, sucrose concentrations in the taproots were significantly reduced.
TL;DR: Electrofused protoplasts of Primula malacoides cv ‘Lovely Tokyo’ were electrofused with cell suspension-derived protoplast of P. obconica to produce somatic hybrids, suggesting that the elimination of genetic materials or polyploidization had occurred in some of the hybrid plants obtained.
TL;DR: It is concluded that the clonal propagation of Arnica montana is obtained, because the pattern of several individuals belonging to different clones was the same, and only one region with esterase activity that is present in all individuals has been identified.
Abstract: Micropropagation of Arnica montana L. using Murashige and Skoog (MS) medium supplemented with N6-[2-isopentenyl]adenine (2iP), zeatin and α-naphthaleneacetic acid (NAA) in different concentrations does not ensure the formation of a high number of regenerated plants; a maximum of 3.2 neoplantlets per explant were obtained. After 4 wk of culture on medium with zeatin (4.5 μM) and NAA (5.3 μM), plants were 3.06 cm in length. The following step was to improve the clonal propagation of this species. Micropropagation of Arnica montana L., initiated from nodal segments using semisolid media (4 g l−1 agar), was obtained. Explants were inoculated on MS medium supplemented with NAA (5.3 μM), 2iP (5.0 μM), maize extract (1.0 ml l−1), phloroglucinol (0.6 mM) or adenine sulfate (0.2 mM). Only 3 wk after the inoculation, plant multiplication as well as induction of roots were obtained, the optimal variant being that containing NAA (5.3 μM), 2iP (5.0 μM) and maize extract (1.0 ml l−1). Six weeks after the inoculation plants were transferred to Perlite, with 80% plant survival being obtained. By isoesterase pattern we concluded that we have obtained the clonal propagation of Arnica montana, because the pattern of several individuals belonging to different clones was the same. Only one region with esterase activity that is present in all individuals has been identified.
TL;DR: It is suggested that the mutant leaves comprised the pathways of the ethylene signal reception and transduction, which provided for the acceleration of their senescence, and the level of endogenous cytokinins determined the rate ofsenescence and the leaf response to cytokinin treatment.
Abstract: We studied the effects of cytokinin benzyladenine (BA) and ethylene on the senescence in the dark of detached leaves of Arabidopsis thaliana(L.) Heynh wild-type plants and theeti-5mutant, which was described in the literature as the ethylene-insensitive one. Leaf senescence was assessed from a decrease in the chlorophyll content. The content of endogenous cytokinins (zeatin and zeatin riboside) was estimated by the ELISA technique. We demonstrated that the content of endogenous cytokinins in the leaves of the three-week-old eti-5mutants exceeded that of the wild-type leaves by an order of magnitude; in the five-week-old mutants, by several times; and in the seven-week-old plants, the difference became insignificant. Due to the excess of endogenous cytokinins in the three–five-week-old mutant leaves, their senescence in the dark was retarded and exogenous cytokinin affected these leaves to a lesser extent. The seven-week-old mutant and the wild-type leaves, which contained practically similar amounts of endogenous cytokinins, did not differ in these indices. Thus, the level of endogenous cytokinins determined the rate of senescence and the leaf response to cytokinin treatment. Ethylene accelerated the senescence of detached wild-type leaves. Ethylene action increased with increasing its concentration from 0.1 to 100 μl/l. BA (10–6M) suppressed ethylene action. Similar data were obtained for the eti-5mutant leaves. We therefore suggest that the mutant leaves comprised the pathways of the ethylene signal reception and transduction, which provided for the acceleration of their senescence.
Journal Article•
TL;DR: F fungi used in this study showed that they synthesized GA3, ABA and zeatin as a primary or secondary metabolite and these plant hormones were found to be in free and bounded forms.
Abstract: The levels of endogenous form of free, bound and total-gibberellic acid (GA3), abscisic acid (ABA) and cytokinin (zeatin) in culture medium were determined. The changes in dry weight of the mycelium, dependent on the culture periods, was examined through the use of white-rot fungus Lentinus tigrinus and brown-rot fungus Laetiporus sulphureus which were cultured in the medium of olive oil mill waste in a static culture. Spectrophotometric techniques were used to determine the amounts of endogenous GA3, ABA and zeatin. As a result, fungi used in this study showed that they synthesized GA3, ABA and zeatin as a primary or secondary metabolite and these plant hormones were found to be in free and bounded forms.