Articoli di riviste: "Gibberellins Metabolism"

1

Hedden, Peter. "The Current Status of Research on Gibberellin Biosynthesis". Plant and Cell Physiology 61, n. 11 (11 luglio 2020): 1832–49. http://dx.doi.org/10.1093/pcp/pcaa092.

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Abstract Gibberellins are produced by all vascular plants and several fungal and bacterial species that associate with plants as pathogens or symbionts. In the 60 years since the first experiments on the biosynthesis of gibberellic acid in the fungus Fusarium fujikuroi, research on gibberellin biosynthesis has advanced to provide detailed information on the pathways, biosynthetic enzymes and their genes in all three kingdoms, in which the production of the hormones evolved independently. Gibberellins function as hormones in plants, affecting growth and differentiation in organs in which their concentration is very tightly regulated. Current research in plants is focused particularly on the regulation of gibberellin biosynthesis and inactivation by developmental and environmental cues, and there is now considerable information on the molecular mechanisms involved in these processes. There have also been recent advances in understanding gibberellin transport and distribution and their relevance to plant development. This review describes our current understanding of gibberellin metabolism and its regulation, highlighting the more recent advances in this field.

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Zhang, L., S. Rajapakse, R. E. Ballard e N. C. Rajapakse. "Light Quality Regulation of Gene Expression in Chrysanthemum". HortScience 33, n. 3 (giugno 1998): 446c—446. http://dx.doi.org/10.21273/hortsci.33.3.446c.

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A major part of Clemson light quality research program focuses on understanding the mechanisms of plant growth alteration under spectral filters. We have extended this research to understand the molecular basis for plant height control by spectral filters. From the whole plant research we have found that gibberellins (GA) play a key role in height control under spectral filters. However, it is not clear whether an alteration of endogenous gibberellin levels or a change in sensitivity to gibberellins is causing the observed effects. Since gibberellins are a key hormone in cell expansion and flower development, an understanding of gibberellin regulation and metabolism under spectral filters is critical for the control of height and flowering of plants grown under these filters. For the molecular study, we have selected the gene that code for enzyme GA 20-oxidase, one of the key enzymes involved in producing functional GAs in the mevalonic acid pathway. GA 20-oxidase is thought to be a site of regulation of GA synthesis by the environment. We are currently studying the regulation of the expression of this gene by light quality using Northern analysis. Results from temporal and tissue specific regulation of chrysanthemum plants grown under CuSO4 filters will be presented.

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Han, Jennifer, Jan E. Murray, Qingyi Yu, Paul H. Moore e Ray Ming. "The Effects of Gibberellic Acid on Sex Expression and Secondary Sexual Characteristics in Papaya". HortScience 49, n. 3 (marzo 2014): 378–83. http://dx.doi.org/10.21273/hortsci.49.3.378.

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The vegetative forms of male (XY), female (XX), and hermaphrodite (XYh) papaya (Carica papaya L.) plants are phenotypically identical. However, the flower and inflorescence morphology of each sex type is unique. Gynodioecious varieties SunUp, SunUp Diminutive mutant, and dioecious AU9 were used to test the response of papaya to gibberellic acid (GA3). Exogenous applications of GA3 on female and hermaphrodite flowers of papaya did not yield any sex reversal phenotype but caused a significant increase in peduncle elongation and inflorescence branch number in all treated plants. An increase in flower number was seen in females but not hermaphrodites or males. There was an increase in plant height for all treated plants except SunUp Diminutive mutant, suggesting that the mechanism causing the dwarf phenotype is independent of gibberellins. Gibberellin metabolism genes were identified in the papaya genome, none of which mapped to the sex-determining region of either the male- or hermaphrodite-specific region of papaya Y or Yh chromosome. We hypothesize that a transacting regulatory element that enhances gibberellin biosynthesis plays a role in the extreme length of the male papaya peduncle.

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Valkai, Ildikó, Erzsébet Kénesi, Ildikó Domonkos, Ferhan Ayaydin, Danuše Tarkowská, Miroslav Strnad, Anikó Faragó, László Bodai e Attila Fehér. "The Arabidopsis RLCK VI_A2 Kinase Controls Seedling and Plant Growth in Parallel with Gibberellin". International Journal of Molecular Sciences 21, n. 19 (1 ottobre 2020): 7266. http://dx.doi.org/10.3390/ijms21197266.

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The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using a T-DNA insertion mutant and RNA interference. Loss of RLCK VI_A2 function resulted in restricted cell expansion and seedling growth. Although these phenotypes could be rescued by exogenous gibberellin, the mutant did not exhibit lower levels of active gibberellins nor decreased gibberellin sensitivity. Transcriptome analysis confirmed that gibberellin is not the direct target of the kinase; its absence rather affected the metabolism and signalling of other hormones such as auxin. It is hypothesized that gibberellins and the RLCK VI_A2 kinase act in parallel to regulate cell expansion and plant growth. Gene expression studies also indicated that the kinase might have an overlapping role with the transcription factor circuit (PIF4-BZR1-ARF6) controlling skotomorphogenesis-related hypocotyl/cotyledon elongation. Furthermore, the transcriptomic changes revealed that the loss of RLCK VI_A2 function alters cellular processes that are associated with cell membranes, take place at the cell periphery or in the apoplast, and are related to cellular transport and/or cell wall reorganisation.

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Zhao, Xiao-Ying, Xu-Hong Yu, Xuan-Ming Liu e Chen-Tao Lin. "Light Regulation of Gibberellins Metabolism in Seedling Development". Journal of Integrative Plant Biology 49, n. 1 (gennaio 2007): 21–27. http://dx.doi.org/10.1111/j.1744-7909.2006.00407.x.

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6

Rodríguez-Ortiz, Roberto, M. Carmen Limón e Javier Avalos. "Regulation of Carotenogenesis and Secondary Metabolism by Nitrogen in Wild-Type Fusarium fujikuroi and Carotenoid-Overproducing Mutants". Applied and Environmental Microbiology 75, n. 2 (1 dicembre 2008): 405–13. http://dx.doi.org/10.1128/aem.01089-08.

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ABSTRACT The fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces metabolites of biotechnological interest, such as gibberellins, bikaverins, and carotenoids. Gibberellin and bikaverin productions are induced upon nitrogen exhaustion, while carotenoid accumulation is stimulated by light. We evaluated the effect of nitrogen availability on carotenogenesis in comparison with bikaverin and gibberellin production in the wild type and in carotenoid-overproducing mutants (carS). Nitrogen starvation increased carotenoid accumulation in all strains tested. In carS strains, gibberellin and bikaverin biosynthesis patterns differed from those of the wild type and paralleled the expression of key genes for both pathways, coding for geranylgeranyl pyrophosphate (GGPP) and kaurene synthases for the former and a polyketide synthase for the latter. These results suggest regulatory connections between carotenoid biosynthesis and nitrogen-controlled biosynthetic pathways in this fungus. Expression of gene ggs1, which encodes a second GGPP synthase, was also derepressed in the carS mutants, suggesting the participation of Ggs1 in carotenoid biosynthesis. The carS mutations did not affect genes for earlier steps of the terpenoid pathway, such as fppS or hmgR. Light induced carotenoid biosynthesis in the wild type and carRA and carB levels in the wild-type and carS strains irrespective of nitrogen availability.

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7

Yang, Y. Y., I. Yamaguchi e N. Murofushi. "Metabolism and Translocation of Gibberellins in the Seedlings of Pharbitis nil (II). Photoperiodic Effects on Metabolism and Translocation of Gibberellins Applied to Cotyledons". Plant and Cell Physiology 37, n. 1 (1 gennaio 1996): 69–75. http://dx.doi.org/10.1093/oxfordjournals.pcp.a028915.

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8

Sun, Hao, Huiting Cui, Jiaju Zhang, Junmei Kang, Zhen Wang, Mingna Li, Fengyan Yi, Qingchuan Yang e Ruicai Long. "Gibberellins Inhibit Flavonoid Biosynthesis and Promote Nitrogen Metabolism in Medicago truncatula". International Journal of Molecular Sciences 22, n. 17 (27 agosto 2021): 9291. http://dx.doi.org/10.3390/ijms22179291.

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Bioactive gibberellic acids (GAs) are diterpenoid plant hormones that are biosynthesized through complex pathways and control various aspects of growth and development. Although GA biosynthesis has been intensively studied, the downstream metabolic pathways regulated by GAs have remained largely unexplored. We investigated Tnt1 retrotransposon insertion mutant lines of Medicago truncatula with a dwarf phenotype by forward and reverse genetics screening and phylogenetic, molecular, biochemical, proteomic and metabolomic analyses. Three Tnt1 retrotransposon insertion mutant lines of the gibberellin 3-beta-dioxygenase 1 gene (GA3ox1) with a dwarf phenotype were identified, in which the synthesis of GAs (GA3 and GA4) was inhibited. Phenotypic analysis revealed that plant height, root and petiole length of ga3ox1 mutants were shorter than those of the wild type (Medicago truncatula ecotype R108). Leaf size was also much smaller in ga3ox1 mutants than that in wild-type R108, which is probably due to cell-size diminution instead of a decrease in cell number. Proteomic and metabolomic analyses of ga3ox1/R108 leaves revealed that in the ga3ox1 mutant, flavonoid isoflavonoid biosynthesis was significantly up-regulated, while nitrogen metabolism was down-regulated. Additionally, we further demonstrated that flavonoid and isoflavonoid biosynthesis was induced by prohexadione calcium, an inhibitor of GA3ox enzyme, and inhibited by exogenous GA3. In contrast, nitrogen metabolism was promoted by exogenous GA3 but inhibited by prohexadione calcium. The results of this study further demonstrated that GAs play critical roles in positively regulating nitrogen metabolism and transport and negatively regulating flavonoid biosynthesis through GA-mediated signaling pathways in leaves.

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Maki, Sonja L., Mark L. Brenner, Paul R. Birnberg, Peter J. Davies e Thomas P. Krick. "Identification of Pea Gibberellins by Studying [14C]GA12-Aldehyde Metabolism". Plant Physiology 81, n. 4 (1 agosto 1986): 984–90. http://dx.doi.org/10.1104/pp.81.4.984.

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10

Heupel, Rick C., Bernard O. Phinney, Clive R. Spray, Paul Gaskin, Jake MacMillan, Peter Hedden e Jan E. Graebe. "Native gibberellins and the metabolism of [14C]gibberellin A53 and of [17-13C, 17-3H2]gibberellin A20 in tassels of Zea mays". Phytochemistry 24, n. 1 (gennaio 1985): 47–53. http://dx.doi.org/10.1016/s0031-9422(00)80805-5.

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Barrero, Alejandro F., J. Enrique Oltra, Eduardo Cabrera, Fernando Reyes e Mı́riam Álvarez. "Metabolism of gibberellins and ent-kaurenoids in mutants of Gibberella fujikuroi". Phytochemistry 50, n. 7 (aprile 1999): 1133–40. http://dx.doi.org/10.1016/s0031-9422(98)00699-2.

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12

Zi, Jiachen, Sibongile Mafu e Reuben J. Peters. "To Gibberellins and Beyond! Surveying the Evolution of (Di)Terpenoid Metabolism". Annual Review of Plant Biology 65, n. 1 (29 aprile 2014): 259–86. http://dx.doi.org/10.1146/annurev-arplant-050213-035705.

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13

Tatineni, Anuradha, Nihal C. Rajapakse, R. Thomas Fernandez e James R. Rieck. "Effectiveness of Plant Growth Regulators under Photoselective Greenhouse Covers". Journal of the American Society for Horticultural Science 125, n. 6 (novembre 2000): 673–78. http://dx.doi.org/10.21273/jashs.125.6.673.

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Responses to selected chemical growth retardants (daminozide, paclobutrazol, and prohexadione-Ca) and GA1 and GA3 under photoselective greenhouse covers with various phytochrome photoequilibrium estimates (φe) were evaluated using `Bright Golden Anne' chrysanthemum [Dendranthema ×grandiflora Kitam. (syn. Chrysanthemum morifolium Ramat.)] as the model plant to better understand the height control mechanism by far red (FR) light depleted environments. Plant height linearly decreased as φe increased from 0.72 to 0.83. The rate of height decrease of daminozide treated plants was less than that of water (control) or GA3-treated plants. The rate of height reduction was not different between control and GA3-treated plants among chambers with various φe. Both paclobutrazol and prohexadione-Ca reduced plant height regardless of φe, but the height reduction by paclobutrazol was more than that by prohexadioneCa. The combination of paclobutrazol and prohexadione-Ca reduced plant height more than either alone. GA1 reversed the height reduction caused by paclobutrazol and prohexadione-Ca regardless of φe, but the height increase by GA1 was more when it was applied with prohexadione-Ca than when applied alone. Results show that photoselective covers with high φe were effective in controlling height of chrysanthemums without chemical growth retardants. The linear relationship between plant height and φe suggests that effectiveness of photoselective covers increased as φe increased. The photosynthetic photon flux (PPF) transmission of photoselective covers decreased as the φe increased because of the increasing dye concentration. Identifying photoselective covers that effectively filter out FR light from sunlight and reduce plant height while minimizing the PPF reduction is critical for commercial success of photoselective covers. Gibberellins are, at least partially, involved in height control by photoselective covers. Photoselective greenhouse covers did not reduce responsiveness to gibberellins, and it appears that the mechanism may be to suppress gibberellin biosynthesis. Results also suggest that increased metabolism of GA1 to GA8 was not the mechanism of height control by photoselective covers. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) [daminozide]; (±)-(R*,R*)-b-((4-chlorophenyl)methyl)-a-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol [paclobutrazol]; 3,5-dioxo-4-(1-oxopropyl)cyclohexanecarboxylic acid [prohexadione-Ca]; gibberellic acid [GA].

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14

Beall, Frederick D., Edward C. Yeung e Richard P. Pharis. "Far-red light stimulates internode elongation, cell division, cell elongation, and gibberellin levels in bean". Canadian Journal of Botany 74, n. 5 (1 maggio 1996): 743–52. http://dx.doi.org/10.1139/b96-093.

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The contributions of cell division and cell elongation and the potential role of gibberellins in the far-red light stimulation of bean internode elongation were investigated. When bean plants, Phaseolus vulgaris cv. Kentucky Wonder, were grown in white light supplemented with far-red light a significant increase, up to threefold, in internode elongation was observed. Microscopic examination revealed that cell lengths were also increased but by a lower magnitude than internode length. Cell-labeling studies with [3H]thymidine showed that nuclei labeling was increased in internodes receiving supplemental far-red light. Thus far-red light induced increased internode elongation is a result of both increased cell elongation and increased cell division. Gibberellins A1, A20, A19, A44, and A4 and kaurenoic acid were identified in extracts of internode tissue by gas chromatography – mass spectroscopy using [2H2]-labeled internal standards for quantification. It thus appears that the early C-13 hydroxylation pathway is operative in the elongating internode. Endogenous GA1 and GA20 were approximately twofold higher in the first internodes of plants receiving supplemental far-red light. A comparison of the metabolism of exogenously supplied [2H2]GA19 suggested that GA turnover was greater in tissues exposed to supplemental far-red light. These results indicate that both cell division and elongation contribute to the enhanced elongation response of bean internodes to far-red light and that these processes are correlated with an increase in GA levels and (or) metabolism. Keywords: Phaseolus, gibberellins, phytochrome, far-red light.

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Kosakivska, I. V. "GIBBERELLINS IN REGULATION OF PLANT GROWTH AND DEVELOPMENT UNDER ABIOTIC STRESSES". Biotechnologia Acta 14, n. 2 (febbraio 2021): 5–18. http://dx.doi.org/10.15407/biotech14.02.005.

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Background. Gibberellins (GAs), a class of diterpenoid phytohormones, play an important role in regulation of plant growth and development. Among more than 130 different gibberellin molecules, only a few are bioactive. GA1, GA3, GA4, and GA7 regulate plant growth through promotion the degradation of the DELLA proteins, a family of nuclear growth repressors – negative regulator of GAs signaling. Recent studies on GAs biosynthesis, metabolism, transport, and signaling, as well as crosstalk with other phytohormones and environment have achieved great progress thanks to molecular genetics and functional genomics. Aim. In this review, we focused on the role of GAs in regulation of plant gtowth in abiotic stress conditions. Results. We represented a key information on GAs biosynthesis, signaling and functional activity; summarized current understanding of the crosstalk between GAs and auxin, cytokinin, abscisic acid and other hormones and what is the role of GAs in regulation of adaptation to drought, salinization, high and low temperature conditions, and heavy metal pollution. We emphasize that the effects of GAs depend primarily on the strength and duration of stress and the phase of ontogenesis and tolerance of the plant. By changing the intensity of biosynthesis, the pattern of the distribution and signaling of GAs, plants are able to regulate resistance to abiotic stress, increase viability and even avoid stress. The issues of using retardants – inhibitors of GAs biosynthesis to study the functional activity of hormones under abiotic stresses were discussed. Special attention was focused on the use of exogenous GAs for pre-sowing priming of seeds and foliar treatment of plants. Conclusion. Further study of the role of gibberellins in the acquisition of stress resistance would contribute to the development of biotechnology of exogenous use of the hormone to improve growth and increase plant yields under adverse environmental conditions.

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Kusnetsov, V. V., A. S. Doroshenko, N. V. Kudryakova e M. N. Danilova. "Role of Phytohormones and Light in De-etiolation". Russian Journal of Plant Physiology 67, n. 6 (18 ottobre 2020): 971–84. http://dx.doi.org/10.1134/s1021443720060102.

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Abstract De-etiolation or transition from etiolated growth (skotomorphogenesis) to photomorphogenesis is one of the most intriguing and intricate stages of plant ontogenesis. It comprises reprogramming of plant cell metabolism, reorganizing the operation of the hormonal system, and altering plant morphology. Dark growth in the soil mainly depends on phytohormones with gibberellins and brassinosteroids playing the leading role; on the soil surface, light as a major exogenous agent starts operating. It inhibits activity of the main repressor of photomorphogenesis (COP1) and regulators of transcription, which govern realization of gibberellin (DELLA) and brassinosteroid (BZR1/BES1) signals and activates trans-factors initiating transition to autotrophic nutrition (for instance, HY5). The strategy of etiolated growth consists in achieving a quick exposure to sunlight at the expense of active elongation of the stem. For transition to autotrophic nutrition, a plant must form a photosynthetic apparatus and protect itself from possible light injury. This review deals with the role of the main regulatory components ensuring etiolated growth and transition to photomorphogenic development.

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Van Den Berg, Jan H., Peter J. Davies, Elmer E. Ewing e Anna Halinska. "Metabolism of Gibberellin A12 and A12-Aldehyde and the Identification of Endogenous Gibberellins in Potato (Solanum tuberosum ssp. Andigena) Shoots". Journal of Plant Physiology 146, n. 4 (luglio 1995): 459–66. http://dx.doi.org/10.1016/s0176-1617(11)82009-2.

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Michniewicz, M., B. Rożej e J. Stopińska. "The influence of nitrogen nutrition on the dynamics of growth and metabolism of endogenous growth regulators in Scotch pine (Pinus silvestris L.) seedlings". Acta Societatis Botanicorum Poloniae 45, n. 4 (2015): 495–510. http://dx.doi.org/10.5586/asbp.1976.044.

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Pine seedlings were cultivated in sterile agar cultures containing nitrogen as NH4Cl. The most pronounced positive effect on the growth of seedlings was affected by N used at a concentration of 50 ppm. After 4 months was stated that nitrogen had only a slight effect on elongation, of .shoots but decreased the length of roots. Nitrogen increased the lenght and number of primary and secondary needles as well as the fresh and dry matter of sboots. It stimulated also the number of lateral roots and the fresh and dry matter of the root system. Stimulation of shoot growth and differentiation as a result of nitrogen treatment was correlated with the increase -of free gibberellins and auxins and decrease of the amount of bound gibberellins and ABA-like inhibitor in shoots. However the effect of N on growth of roots was connected with the increase of auxins, cytokinins and ABA-like inhibitor in these organs.

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Gulden, Robert H., Sheila Chiwocha, Suzanne Abrams, Ian McGregor, Allison Kermode e Steven Shirtliffe. "Response to abscisic acid application and hormone profiles in spring Brassica napus seed in relation to secondary dormancy". Canadian Journal of Botany 82, n. 11 (1 novembre 2004): 1618–24. http://dx.doi.org/10.1139/b04-119.

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The plant hormone abscisic acid (ABA) has been implicated in the inception and maintenance of seed dormancy, while gibberellins promote dormancy breakage and germination in some species. We investigated whether osmotic stress induced secondary dormancy in Brassica napus L. is associated with changes in ABA sensitivity and metabolism, as well as changes in gibberellin levels. Seeds of two genotypes, one with low dormancy potential (LDP) and one with high dormancy potential (HDP) for secondary dormancy, were exposed to a dormancy-inducing osmotic treatment for up to 4 weeks and then germinated in the presence of increasing ABA concentrations. Even at relatively high concentrations of supplied ABA, germination of LDP seed was not inhibited, while relatively low ABA concentrations inhibited the germination of HDP seed after osmotic treatment. Fluridone was highly effective in suppressing secondary dormancy development in HDP seed, but had no effect on germinability in LDP seed. Despite the lack of differences in nonosmotically treated seed, ABA and ABA-glucose ester accumulated to higher levels, and gibberellin A1 accumulated to lower levels, in HDP relative to LDP seed by the end of the osmotic treatment. Our findings indicate an association among ABA sensitivity, biosynthesis and accumulation, and secondary dormancy potential in B. napus seed.Key words: abscisic acid (ABA), Brassica napus, fluridone, induced dormancy, osmotic stress, sensitivity.

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Teichert, Sabine, Julian C. Rutherford, Marieke Wottawa, Joseph Heitman e Bettina Tudzynski. "Impact of Ammonium Permeases MepA, MepB, and MepC on Nitrogen-Regulated Secondary Metabolism in Fusarium fujikuroi". Eukaryotic Cell 7, n. 2 (febbraio 2008): 187–201. http://dx.doi.org/10.1128/ec.00351-07.

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ABSTRACT In Fusarium fujikuroi, the production of gibberellins and bikaverin is repressed by nitrogen sources such as glutamine or ammonium. Sensing and uptake of ammonium by specific permeases play key roles in nitrogen metabolism. Here, we describe the cloning of three ammonium permease genes, mepA, mepB, and mepC, and their participation in ammonium uptake and signal transduction in F. fujikuroi. The expression of all three genes is strictly regulated by the nitrogen regulator AreA. Severe growth defects of ΔmepB mutants on low-ammonium medium and methylamine uptake studies suggest that MepB functions as the main ammonium permease in F. fujikuroi. In ΔmepB mutants, nitrogen-regulated genes such as the gibberellin and bikaverin biosynthetic genes are derepressed in spite of high extracellular ammonium concentrations. mepA mepB and mepC mepB double mutants show a similar phenotype as ΔmepB mutants. All three F. fujikuroi mep genes fully complemented the Saccharomyces cerevisiae mep1 mep2 mep3 triple mutant to restore growth on low-ammonium medium, whereas only MepA and MepC restored pseudohyphal growth in the mep2/mep2 mutant. Overexpression of mepC in the ΔmepB mutants partially suppressed the growth defect but did not prevent derepression of AreA-regulated genes. These studies provide evidence that MepB functions as a regulatory element in a nitrogen sensing system in F. fujikuroi yet does not provide the sensor activity of Mep2 in yeast, indicating differences in the mechanisms by which nitrogen is sensed in S. cerevisiae and F. fujikuroi.

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Wiseman, Nadine J., e Colin G. N. Turnbull. "Endogenous gibberellin content does not correlate with photoperiod-induced growth changes in strawberry petioles". Functional Plant Biology 26, n. 4 (1999): 359. http://dx.doi.org/10.1071/pp98002.

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We have examined whether gibberellins (GAs) mediate photoperiodic growth responses in strawberry (Fragaria × ananassa) by measuring GA content and GA metabolism in petioles with accurately defined growth rates. Gibberellin A1 , GA8 , GA19 , GA20 , GA29 , GA34 , and tentatively GA17 , were identified by gas chromatography–mass spectrometry, and GA4 was detected by selected ion monitoring. Although petiole growth rates were reduced within 2 d of a long-day to short-day transfer, we found no consistent changes in GA content until 8 d, when GA1 , GA8 , GA29 and GA34 were reduced by about two-fold in short days. GA20 concentration was always low regardless of age or treatment, typically 10-fold less than GA1 and 40-fold less than GA19 . Application of paclobutrazol (25 g plant–1 ) reduced growth rate by 43%, somewhat greater than the effect of short days (23%), but resulted in a six-fold decrease in GA1 content, much greater than the maximum two-fold effect of short days. However, paclobutrazol-treated petioles in long and short days differed in growth rate by 30%, yet had no difference in GA1 content. [2H]GA19 and [2H]GA20 were metabolised to GA1 , GA8 and GA29 , although conversion of GA19 was slow. GA4 was converted to GA 34 but not to GA1 or GA8 . Photoperiod had little effect on any of these metabolic steps. For the following reasons, we suggest that the photoperiod growth response is not mediated primarily through altered GA concentrations: (1) a lack of a rapid photoperiod effect on GA concentrations or metabolism, (2) changes in growth before or independent of changes in GA concentrations and (3) a normal photoperiod effect on growth in petioles with artificially lowered GA content.

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Gaion, Lucas Aparecido, Jean Carlos Muniz, Rafael Ferreira Barreto, Victor D’Amico-Damião, Renato de Mello Prado e Rogério Falleiros Carvalho. "Amplification of gibberellins response in tomato modulates calcium metabolism and blossom end rot occurrence". Scientia Horticulturae 246 (febbraio 2019): 498–505. http://dx.doi.org/10.1016/j.scienta.2018.11.032.

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Jacobs, William P., Frederick D. Beall e Richard P. Pharis. "The transport and metabolism of gibberellins A1and A5in excised segments from internodes ofPhaseolus coccineus". Physiologia Plantarum 72, n. 3 (marzo 1988): 529–34. http://dx.doi.org/10.1111/j.1399-3054.1988.tb09161.x.

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Gao, Shaopei, e Chengcai Chu. "Gibberellin Metabolism and Signaling: Targets for Improving Agronomic Performance of Crops". Plant and Cell Physiology 61, n. 11 (6 agosto 2020): 1902–11. http://dx.doi.org/10.1093/pcp/pcaa104.

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Abstract (sommario):

Abstract Gibberellins (GAs) are a class of tetracyclic diterpenoid phytohormones that regulate many aspects of plant development, including seed germination, stem elongation, leaf expansion, pollen maturation, and the development of flowers, fruits and seeds. During the past decades, the primary objective of crop breeding programs has been to increase productivity or yields. ‘Green Revolution’ genes that can produce semidwarf, high-yielding crops were identified as GA synthesis or response genes, confirming the value of research on GAs in improving crop productivity. The manipulation of GA status either by genetic alteration or by exogenous application of GA or GA biosynthesis inhibitors is often used to optimize plant growth and yields. In this review, we summarize the roles of GAs in major aspects of crop growth and development and present the possible targets for the fine-tuning of GA metabolism and signaling as a promising strategy for crop improvement.

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Wang, Hongfeng, Hongjiao Jiang, Yiteng Xu, Yan Wang, Lin Zhu, Xiaolin Yu, Fanjiang Kong, Chuanen Zhou e Lu Han. "Systematic Analysis of Gibberellin Pathway Components in Medicago truncatula Reveals the Potential Application of Gibberellin in Biomass Improvement". International Journal of Molecular Sciences 21, n. 19 (29 settembre 2020): 7180. http://dx.doi.org/10.3390/ijms21197180.

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Gibberellins (GAs), a class of phytohormones, act as an essential natural regulator of plant growth and development. Many studies have shown that GA is related to rhizobial infection and nodule organogenesis in legume species. However, thus far, GA metabolism and signaling components are largely unknown in the model legume Medicago truncatula. In this study, a genome-wide analysis of GA metabolism and signaling genes was carried out. In total 29 components, including 8 MtGA20ox genes, 2 MtGA3ox genes, 13 MtGA2ox genes, 3 MtGID1 genes, and 3 MtDELLA genes were identified in M. truncatula genome. Expression profiles revealed that most members of MtGAox, MtGID1, and MtDELLA showed tissue-specific expression patterns. In addition, the GA biosynthesis and deactivation genes displayed a feedback regulation on GA treatment, respectively. Yeast two-hybrid assays showed that all the three MtGID1s interacted with MtDELLA1 and MtDELLA2, suggesting that the MtGID1s are functional GA receptors. More importantly, M. truncatula exhibited increased plant height and biomass by ectopic expression of the MtGA20ox1, suggesting that enhanced GA response has the potential for forage improvement.

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26

Yang, Young-Yell, Isomaro Yamaguchi, Kiyotoshi Takeno-Wada, Yoshihito Suzuki e Noboru Murofushi. "Metabolism and Translocation of Gibberellins in Seedlings of Pharbitis nil. (I) Effect of Photoperiod on Stem Elongation and Endogenous Gibberellins in Cotyledons and Their Phloem Exudates". Plant and Cell Physiology 36, n. 2 (marzo 1995): 221–27. http://dx.doi.org/10.1093/oxfordjournals.pcp.a078753.

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27

Ridoutt, B. G., e R. P. Pharis. "Metabolism of deuterium- and tritium-labeled gibberellins in cambial region tissues of Eucalyptus globulus stems". Tree Physiology 18, n. 10 (1 ottobre 1998): 659–64. http://dx.doi.org/10.1093/treephys/18.10.659.

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28

Huanpu, Ma, Patrick S. Blake, Gordon Browning e June M. Taylor. "Metabolism of gibberellins A 1 and A 3 in fruits and shoots of Prunus avium". Phytochemistry 56, n. 1 (gennaio 2001): 67–76. http://dx.doi.org/10.1016/s0031-9422(00)00354-x.

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29

Malcolm, Joan M., Alan Crozier, Colin G. N. Turnbull e Einar Jensen. "Metabolism of C19- and C20-gibberellins by cell-free preparations from immature Phaseolus coccineus seed". Physiologia Plantarum 82, n. 1 (maggio 1991): 57–66. http://dx.doi.org/10.1034/j.1399-3054.1991.820108.x.

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30

Malcolm, Joan M., Alan Crozier, Colin G. N. Turnbull e Einar Jensen. "Metabolism of C19- and C20-gibberellins by cell-free preparations from immature Phaseolus coccineus seed". Physiologia Plantarum 82, n. 1 (maggio 1991): 57–66. http://dx.doi.org/10.1111/j.1399-3054.1991.tb02902.x.

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31

Maki, Sonja L., Sriyani Rajapakse, Robert E. Ballard e Nihal C. Rajapakse. "Role of Gibberellins in Chrysanthemum Growth under Far Red Light-deficient Greenhouse Environments". Journal of the American Society for Horticultural Science 127, n. 4 (luglio 2002): 639–43. http://dx.doi.org/10.21273/jashs.127.4.639.

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Abstract (sommario):

Plants grown in far red (FR) light deficient environments are typically shorter because of short internodes, resembling plants treated with GA biosynthesis inhibitors. The role of GAs in the reduction of stem elongation of `Bright Golden Anne' chrysanthemum [Dendranthem ×grandiflora (Ramat.) Kitam. (syn. Chrysanthemum ×morifolium Ramat.)] grown in FR light deficient (-FR) environment was investigated by following the response of chrysanthemums grown in - FR environment to exogenous application of GA1, GA19, or GA20, and the metabolism of GA12 and GA19 in -FR or +FR environment. FR light deficient environment resulted in 25% to 30% shorter plants than in +FR environment. Final height of GA1- and GA20-treated plants followed a quadratic pattern while that of GA19 treated plants followed a linear pattern as the dosage increased from 0 to 50 μg/apex. The response to GA1 was the greatest followed by GA20 and GA19, regardless of the light environment. Application of GA1 (50 μg/apex) increased final height by 65% compared with no GA (0 μg/apex) application under either +FR or -FR light environment, suggesting the response to GA1, which is the active form, remained the same. Responses to GA19 and GA20 declined under -FR light. [14 C]GA12 and [14C]GA19 metabolized slowly in the -FR environment suggesting that the turnover of GAs may have caused in part the lower response to GA19. Although metabolism of GA1 under -FR environments was not investigated, observations with GA1 application experiments support that -FR environment may have enhanced inactivation of GA1. Chemical name used: gibberellic acid (GA).

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32

Lin, Yuanxiu, Chunyan Wang, Xiao Wang, Maolan Yue, Yunting Zhang, Qing Chen, Mengyao Li et al. "Comparative transcriptome analysis reveals genes and pathways associated with anthocyanins in strawberry". Journal of Berry Research 11, n. 2 (14 giugno 2021): 317–32. http://dx.doi.org/10.3233/jbr-200685.

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BACKGROUND: Anthocyanins are not only one of the most important antioxidants in plants but also responsible for the coloration in strawberry (Fragaria×ananassa), it is suggested to be associated with ascorbic acid (AsA), sugars and plant hormones metabolism. OBJECTIVE: To elucidate the molecular differences of genes and pathways in the presence and absence of anthocyanins. METHODS: RNA sequencing (RNAseq) of red-fleshed strawberry ‘Benihoppe’ and its white-fleshed mutant ‘Xiaobai’ was performed. RESULTS: A total of 1,156 and 1,378 transcripts were differentially expressed (DE) in two cultivars at white stage and red stage respectively. Among them, 28, 49 and 72 DE transcripts were involved in AsA, sugars metabolism and plant hormones signaling respectively. Fruits of ‘Benihoppe’ with higher anthocyanins content contained higher AsA, the expression of D-galacturonate reductase (GalUR) in white-fleshed strawberry was down-regulated. Particularly, the expression of transcripts involved in sugars, jasmonic acid (JA) and abscisic acid (ABA) signaling was decreased, by contrast, the expression of transcripts involved in auxin and gibberellins (GAs) signaling was significantly increased. CONCLUSIONS: The lower AsA level in white-fleshed strawberry is possibly because of the lower flux of D-galacturonate biosynthesis pathway. Anthocyanins was associated with gene expression involved in AsA, sugars, and hormones signaling metabolisms.

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33

Oden, P. C., Q. Wang, K. A. Hogberg e M. Werner. "Transport and metabolism of gibberellins in relation to flower bud differentiation in Norway spruce (Picea abies)". Tree Physiology 15, n. 7-8 (1 luglio 1995): 451–56. http://dx.doi.org/10.1093/treephys/15.7-8.451.

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34

Mino, Masanobu, Mariko Oka, Yasushi Tasaka e Masaki Iwabuchi. "Molecular Biology of the Metabolism and Signal Transduction of Gibberellins, and Possible Applications to Crop Improvement". Journal of Crop Improvement 18, n. 1-2 (17 ottobre 2006): 365–89. http://dx.doi.org/10.1300/j411v18n01_04.

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35

Hedden, Peter, e Stephen G. Thomas. "Gibberellin biosynthesis and its regulation". Biochemical Journal 444, n. 1 (26 aprile 2012): 11–25. http://dx.doi.org/10.1042/bj20120245.

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Abstract (sommario):

The GAs (gibberellins) comprise a large group of diterpenoid carboxylic acids that are ubiquitous in higher plants, in which certain members function as endogenous growth regulators, promoting organ expansion and developmental changes. These compounds are also produced by some species of lower plants, fungi and bacteria, although, in contrast to higher plants, the function of GAs in these organisms has only recently been investigated and is still unclear. In higher plants, GAs are synthesized by the action of terpene cyclases, cytochrome P450 mono-oxygenases and 2-oxoglutarate-dependent dioxygenases localized, respectively, in plastids, the endomembrane system and the cytosol. The concentration of biologically active GAs at their sites of action is tightly regulated and is moderated by numerous developmental and environmental cues. Recent research has focused on regulatory mechanisms, acting primarily on expression of the genes that encode the dioxygenases involved in biosynthesis and deactivation. The present review discusses the current state of knowledge on GA metabolism with particular emphasis on regulation, including the complex mechanisms for the maintenance of GA homoeostasis.

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36

Ribeiro, Dimas M., Wagner L. Araújo, Alisdair R. Fernie, Jos H. M. Schippers e Bernd Mueller-Roeber. "Action of Gibberellins on Growth and Metabolism of Arabidopsis Plants Associated with High Concentration of Carbon Dioxide". Plant Physiology 160, n. 4 (22 ottobre 2012): 1781–94. http://dx.doi.org/10.1104/pp.112.204842.

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37

Sponsel, V. M. "Gibberellins in dark- and red-light-grown shoots of dwarf and tall cultivars of Pisum sativum: The quantification, metabolism and biological activity of gibberellins in Progress no. 9 and Alaska". Planta 168, n. 1 (maggio 1986): 119–29. http://dx.doi.org/10.1007/bf00407018.

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38

Yang, Xiaohua, Susan K. Brown e Peter J. Davies. "The Content and In Vivo Metabolism of Gibberellin in Apple Vegetative Tissues". Journal of the American Society for Horticultural Science 138, n. 3 (maggio 2013): 173–83. http://dx.doi.org/10.21273/jashs.138.3.173.

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Despite the demonstrated importance of gibberellins (GAs) as regulators of fruit tree stature, information on their in vivo metabolism in apple vegetative tissues is still lacking. To determine whether the GA content and metabolism differs between dwarf and standard phenotypes and the influence of rootstocks, [14C]GA12, a common precursor of all GAs in higher plants, was applied to vigorously growing apple (Malus ×domestica) shoots collected from the scion cultivar Redcort on MM.106, a growth-promoting rootstock, and dwarf and standard seedlings on their own roots from progeny 806 (a cross between a breeding selection with reduced stature and an advanced breeding selection with a standard tree form). Twenty-one metabolites were identified by high-performance liquid chromatography (HPLC) and used as tracers for the purification of endogenous GAs. The existence of endogenous and [2H]-labeled GA12, GA15, GA53, GA44, GA19, GA20, and GA3 was demonstrated by gas chromatography–mass spectrometry (GC-MS); GA20 was the major GA present, with slightly less GA19 and GA44, and with GA3 present at approximately one-third the level of GA20. Despite specific searching, neither GA4, GA7, GA1, nor GA29 was found, showing that [14C]GA12 is metabolized mainly through the 13-hydroxylation pathway and that GA3 is a bioactive GA in apple vegetative tissues. The invigorating rootstock led to a slow GA metabolic rate in ‘Redcort’. For self-rooted plants, the same GAs were identified in dwarf and standard seedlings from progeny 806, although standard plants metabolized at twice the speed of dwarf plants. Young branches of dwarf 806 plants treated with GA3 were one-third longer with more nodes but similar in internode length. We conclude that the dwarf phenotype in progeny 806 is not caused by a lack of certain GAs in the GA biosynthesis pathway downstream of GA12.

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39

Iglesias-Fernández, Raquel, e Angel J. Matilla. "Genes involved in ethylene and gibberellins metabolism are required for endosperm-limited germination of Sisymbrium officinale L. seeds". Planta 231, n. 3 (10 dicembre 2009): 653–64. http://dx.doi.org/10.1007/s00425-009-1073-5.

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40

Bianco, J., G. Garello e M. T. Le Page-Degivry. "Release of dormancy in sunflower embryos by dry storage: involvement of gibberellins and abscisic acid". Seed Science Research 4, n. 2 (giugno 1994): 57–62. http://dx.doi.org/10.1017/s0960258500002026.

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AbstractExcised Helianthus annuus L. embryos became dormant during the third week after anthesis. At this stage a short drying treatment (3 d) led to a slight improvement in germination but a 6-week dry storage caused a complete release from dormancy. The short drying treatment, however, elicited the embryos' response to an exogenous concentration of GAs which was unable to promote germination of fresh embryos. It therefore appeared that a short drying treatment changed the sensitivity to GAs but was not capable of directing embryo metabolism completely towards a germinative mode. Moreover, this drying treatment reduced considerably the ABA content in both the axis and the embryo. Nevertheless, no correlation could be established between germinability and the ABA content since the amount of ABA was not modified by the 6-week dry storage. The key step for predisposing the seeds to germinate is the suppression of the capacity for ABA synthesis in the axis, a suppression which takes place during 6-week dry storage.

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41

Litvin, Alexander G., Marc W. van Iersel e Anish Malladi. "Drought Stress Reduces Stem Elongation and Alters Gibberellin-related Gene Expression during Vegetative Growth of Tomato". Journal of the American Society for Horticultural Science 141, n. 6 (novembre 2016): 591–97. http://dx.doi.org/10.21273/jashs03913-16.

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Abstract (sommario):

Drought stress reduces stem elongation and cell expansion. Since gibberellins (GAs) play an important role in controlling cell elongation, the objective of this study was to determine if the reduction in growth under drought stress is associated with altered GA metabolism or signaling. We exposed ‘Moneymaker’ tomato (Solanum lycopersicum) to drought stress to observe the effects on growth. Irrigation was automated using a data logger, which maintained volumetric water contents (VWC) of 0.35 and 0.15 m3·m−3 for well-watered and drought-stressed conditions, respectively. To further investigate the effect of GAs on elongation, paclobutrazol (PAC), a GA biosynthesis inhibitor, was applied to reduce endogenous GA production. Drought stress and PAC treatment reduced plant height. Internode length, cell size, and shoot dry weight displayed an interaction between the VWC and PAC treatments. The transcript levels of SlGA20ox1, -2, -3, and -4, SlGA3ox2, and SlGA2ox2, -4, and -5, corresponding to enzymes in GA metabolism, and LeEXP1, and -2, encoding expansin enzymes related to cell wall loosening necessary for cell expansion, were analyzed. Downregulation of transcript accumulation due to drought stress was observed for SlGA20ox4, SlGA2ox5, and LeEXP1, but not for any of the other genes. PAC increased expression of SlGA20ox-3, and SlGA3ox2, potentially through feedback regulation. These findings suggest that drought stress effects on elongation are at least partly mediated by altered GA metabolism.

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42

Macdonald, S. Ellen, David M. Reid e C. C. Chinnappa. "Studies on the Stellaria longipes complex: phenotypic plasticity. II. Gibberellins, abscisic acid, and stem elongation". Canadian Journal of Botany 64, n. 11 (1 novembre 1986): 2617–21. http://dx.doi.org/10.1139/b86-346.

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Clonal material of one genotype of Stellaria longipes Goldie s.l. was used to investigate whether environmental regulation of the phenotype was mediated through phytohormones. Photoperiod and temperature modified the response of this species to exogenous application of gibberellins (GAs) and abscisic acid (ABA). Application of GAs to ramets in short or long days and low temperature increased stem elongation but did not induce elongation equivalent to that seen in control ramets in long warm days. Application of GAs to ramets in short days (warm or cold) induced elongation equivalent to that of ramets in long days at a similar temperature. Application of (2-chloroethyl)-trimethylammonium chloride resulted in dwarfing at some concentrations, while exposure to other concentrations initially stimulated elongation. Application of ABA reduced elongation in short, cold days but showed no effect under other conditions. Metabolism of radiolabeled ABA and GA3 was similar in both short cold days and long warm days. It was concluded that photoperiodically induced stem elongation could be partially mediated through endogenous levels of GAs. However, a hypothesis based on the idea that temperature-induced changes in elongation are controlled by suboptimal levels of GAs or supraoptimal levels of ABA is inadequate.

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43

Kössler, Stella, Tegan Armarego-Marriott, Danuše Tarkowská, Veronika Turečková, Shreya Agrawal, Jianing Mi, Leonardo Perez de Souza et al. "Lycopene β-cyclase expression influences plant physiology, development, and metabolism in tobacco plants". Journal of Experimental Botany 72, n. 7 (23 gennaio 2021): 2544–69. http://dx.doi.org/10.1093/jxb/erab029.

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Abstract Carotenoids are important isoprenoids produced in the plastids of photosynthetic organisms that play key roles in photoprotection and antioxidative processes. β-Carotene is generated from lycopene by lycopene β-cyclase (LCYB). Previously, we demonstrated that the introduction of the Daucus carota (carrot) DcLCYB1 gene into tobacco (cv. Xanthi) resulted in increased levels of abscisic acid (ABA) and especially gibberellins (GAs), resulting in increased plant yield. In order to understand this phenomenon prior to exporting this genetic strategy to crops, we generated tobacco (Nicotiana tabacum cv. Petit Havana) mutants that exhibited a wide range of LCYB expression. Transplastomic plants expressing DcLCYB1 at high levels showed a wild-type-like growth, even though their pigment content was increased and their leaf GA1 content was reduced. RNA interference (RNAi) NtLCYB lines showed different reductions in NtLCYB transcript abundance, correlating with reduced pigment content and plant variegation. Photosynthesis (leaf absorptance, Fv/Fm, and light-saturated capacity of linear electron transport) and plant growth were impaired. Remarkably, drastic changes in phytohormone content also occurred in the RNAi lines. However, external application of phytohormones was not sufficient to rescue these phenotypes, suggesting that altered photosynthetic efficiency might be another important factor explaining their reduced biomass. These results show that LCYB expression influences plant biomass by different mechanisms and suggests thresholds for LCYB expression levels that might be beneficial or detrimental for plant growth.

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44

Rademacher*, Wilhelm. "Prohexadione-Ca in Fruit Trees: Modes of Action of a Multifunctional Bioregulator". HortScience 39, n. 4 (luglio 2004): 851D—851. http://dx.doi.org/10.21273/hortsci.39.4.851d.

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Abstract (sommario):

APOGEE and REGALIS have recently been introduced in a number of countries for use in pome and other fruit trees. These products contain 27.5% and 10% of prohexadione-Ca (ProCa), respectively. As a result of inhibiting excessive vegetative growth, less summer and dormant pruning is required, the ratio between vegetative growth and fruit formation is improved, and crop protection is facilitated due to the reduction of tree row volume and a more open canopy. Additionally, a lowered incidence of diseases such as fire blight and scab is observed, which is not due to a direct bactericidal or fungicidal effect of the compound. Further, the compound may reduce fruit drop early in the season. Prohexadione is a structural mimic of 2-oxoglutaric and ascorbic acid. Therefore, distinct dioxygenases are blocked, which require these compounds as a co-substrate. Such enzymes catalyze late steps in gibberellin biosynthesis. After treatment with ProCa, less growth-active gibberellins are formed and treated plants remain more compact. ProCa also affects ACC oxidase, another dioxygenase. The resulting reduction of ethylene formation, in addition to the availability of more assimilates for fruit growth, is most likely the cause of reduced fruit drop. 2-Oxoglutaric acid-dependent dioxygenases are also involved in the metabolism of flavonoids and their phenolic precursors: In shoots of apples and pears, ProCa causes considerable changes by inhibiting flavanone 3-hydroxylase. Convincing evidence is now available that ProCa triggers pathogen resistance by inducing the formation of 3-deoxyflavonoids, in particular luteoforol, with phytoalexin-like properties. Morphoregulatory effects caused by ProCa are only of secondary relevance for the reduction of disease incidence.

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45

Turnbull, Matthew H., Richard P. Pharis, Leonid V. Kurepin, Michal Sarfati, Lewis N. Mander e Dave Kelly. "Flowering in snow tussock (Chionochloa spp.) is influenced by temperature and hormonal cues". Functional Plant Biology 39, n. 1 (2012): 38. http://dx.doi.org/10.1071/fp11116.

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Snow tussocks (Chionochloa spp.) in New Zealand exhibit extreme mast (episodic) seeding which has important implications for plant ecology and plant–insect interactions. Heavy flowering appears to be triggered by very warm/dry summers in the preceding year. In order to investigate the physiological basis for mast flowering, mature snow tussock plants in the field and younger plants in a glasshouse and shadehouse were subjected to a range of manipulative treatments. Field treatments included combinations of warming, root pruning and applications of two native gibberellins (GAs) GA3, which is known to be highly floral inductive and GA4, which is associated with continued floral apex development in another long-day grass. Warming, GA3 alone and especially warming + GA3, significantly promoted flowering, as did applications of GA4 alone and GA4 + CCC (2-chloroethyltrimethylammonium chloride, which is a known synergist of GA3-induced flowering in the annual grass, Lolium temulentum L.). Our results provide support for the concept that mast flowering events in tussock species are causally related to high temperature-induced increases in endogenous gibberellin levels. It is likely that GAs (endogenous or applied) promote the continued development of a previously long-day induced floral apex. In addition to the promotion of flowering, applied GA3 also disturbed the plant’s innate resource threshold requirements, as shown by the death, over winter, of many non-flowering tillers. Applied GA4 did not show this effect, likely due to its rapid catabolic metabolism to an inactive form. High temperature-induced flowering mediated by elevated levels of endogenous floral-promotive GAs could have important implications for regulating the evolutionary interaction between these masting plants and their seed predators.

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46

Reinoso, Herminda, Virginia Luna, Carlos Dauría, Richard P. Pharis e Rubén Bottini. "Dormancy in peach (Prunus persica) flower buds. VI. Effects of gibberellins and an acylcyclohexanedione (trinexapac-ethyl) on bud morphogenesis in field experiments with orchard trees and on cuttings". Canadian Journal of Botany 80, n. 6 (1 giugno 2002): 664–74. http://dx.doi.org/10.1139/b02-051.

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Abstract (sommario):

The effects of several gibberellins (GAs), exo-16,17-dihydro GA5, 2,2-dimethyl GA4, and GA3, and trinexapac-ethyl (an acylcyclohexanedione inhibitor of late-stage GA biosynthesis), were assessed for their effects on flower bud development during and after winter dormancy in peach (Prunus persica (L.) Batsch.) in three field trials and one experiment using cuttings. At late developmental stages, GA3 hastened floral bud development and shortened the time to anthesis, whereas early-stage applications of GA3 either had no effect or delayed floral bud development. In contrast, an exceptionally growth-active GA, 2,2-dimethyl GA4, promoted floral bud development (tested only on cuttings) across a range of application dates. However, it also induced a high percentage of bud abscission and remaining buds had a necrotic gynoecium and alterations in the androecium. Surprisingly, trinexapac-ethyl also promoted floral bud development, although it was not as effective as GA1. Trinexapac-ethyl-treated buds also showed morphological alterations and gynoecium necrosis. However, the best and most consistent treatment for enhancing floral bud development and hastening flower anthesis was 16,17-dihydro GA5. It stimulated floral bud development in up to 80% of the treated buds. Further, the promotive effect of 16,17-dihydro GA5 was maintained through to anthesis across three years of field experiments on intact trees, as well as with cuttings. Whether 16,17-dihydro GA5, a competitive inhibitor of the 3β-hydroxylation step in GA biosynthesis, acts per se, acts via a metabolite (such as 16,17-dihydro GA3), or acts by modifying endogenous GA metabolism is not yet known.Key words: gibberellins, trinexapac-ethyl, floral bud morphogenesis, peach.

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47

Zanewich, Karen P., e Stewart B. Rood. "Gibberellins and Heterosis in Crops and Trees: An Integrative Review and Preliminary Study with Brassica". Plants 9, n. 2 (22 gennaio 2020): 139. http://dx.doi.org/10.3390/plants9020139.

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Heterosis, or hybrid vigor, has contributed substantially to genetic improvements in crops and trees and its physiological basis involves multiple processes. Four associations with the phytohormone gibberellin (GA) indicate its involvement in the regulation of heterosis for shoot growth in maize, sorghum, wheat, rice, tomato and poplar. (1) Inbreds somewhat resemble GA-deficient dwarfs and are often highly responsive to exogenous GA3. (2) Levels of endogenous GAs, including the bioeffector GA1, its precursors GA19 and GA20, and/or its metabolite GA8, are higher in some fast-growing hybrids than parental genotypes. (3) Oxidative metabolism of applied [3H]GAs is more rapid in vigorous hybrids than inbreds, and (4) heterotic hybrids have displayed increased expression of GA biosynthetic genes including GA 20-oxidase and GA 3-oxidase. We further investigated Brassica rapa, an oilseed rape, by comparing two inbreds (AO533 and AO539) and their F1 hybrid. Seedling emergence was faster in the hybrid and potence ratios indicated dominance for increased leaf number, area and mass, and stem mass. Overdominance (heterosis) was displayed for root mass, leading to slight heterosis for total plant mass. Stem contents of GA19,20,1 were similar across the Brassica genotypes and increased prior to bolting; elongation was correlated with endogenous GA but heterosis for shoot growth was modest. The collective studies support a physiological role for GAs in the regulation of heterosis for shoot growth in crops and trees, and the Brassica study encourages further investigation of heterosis for root growth.

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48

Wang, Q., C. H. A. Little, T. Moritz e P. C. Oden. "Identification of endogenous gibberellins, and metabolism of tritiated and deuterated GA4, GA9 and GA20, in Scots pine (Pinus sylvestris) shoots". Physiologia Plantarum 97, n. 4 (agosto 1996): 764–71. http://dx.doi.org/10.1034/j.1399-3054.1996.970418.x.

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49

Koshioka, Masaji, Alan Jones e Richard P. Pharis. "The Potential of Cell Suspension Cultures ofDaucus carotaL. as a Source of Isotope Labelled Gibberellins. I. Metabolism of [3H]GA5". Agricultural and Biological Chemistry 52, n. 1 (gennaio 1988): 55–61. http://dx.doi.org/10.1080/00021369.1988.10868608.

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50

Wang, Q., C. H. A. Little, T. Moritz e P. C. Oden. "Identification of endogenous gibberellins, and metabolism of tritiated and deuterated GA4, GA9 and GA20, in Scots pine (Pinus sylvestris) shoots". Physiologia Plantarum 97, n. 4 (agosto 1996): 764–71. http://dx.doi.org/10.1111/j.1399-3054.1996.tb00542.x.

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