Spatial pattern of cauliflower mosaic virus 35S promoter-luciferase expression in transgenic hybrid aspen trees monitored by enzymatic assay and non-destructive imaging

Nilsson, Ove; Aldén, Torsten; Sitbon, Folke; Little, C. H. A.; Chalupa, V.; Sandberg, Göran; Olsson, Olof

doi:10.1007/bf02524751

Cited by 130 publications

(117 citation statements)

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“…The construct was transformed into hybrid aspen, Populus tremula 3 Populus tremuloides Michx. clone T89, and plants were regenerated essentially as previously described (Nilsson et al, 1992). Following an initial characterization of 12 transgenic lines, five representative lines were chosen for further studies.…”

Section: Plant Transformation and Growth Conditionsmentioning

confidence: 99%

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

et al. 2004

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To broaden our understanding of gibberellin (GA) biosynthesis and the mechanism whereby GA homeostasis is maintained in plants, we have investigated the degree to which the enzyme GA 3-oxidase (GA3ox) limits the formation of bioactive GAs in elongating shoots of hybrid aspen (Populus tremula 3 Populus tremuloides). We describe the cloning of a hybrid aspen GA3ox and its functional characterization, which confirmed that it has 3b-hydroxylation activity and more efficiently converts GA 9 to GA 4 than GA 20 to GA 1 . To complement previous studies, in which transgenic GA 20-oxidase (GA20ox) overexpressers were found to produce 20-fold higher bioactive GA levels and subsequently grew faster than wild-type plants, we overexpressed an Arabidopsis GA3ox in hybrid aspen. The generated GA3ox overexpresser lines had increased 3b-hydroxylation activity but exhibited no major changes in morphology. The nearly unaltered growth pattern was associated with relatively small changes in GA 1 and GA 4 levels, although tissue-dependent differences were observed. The absence of increases in bioactive GA levels did not appear to be due to feedback or feed-forward regulation of dioxygenase transcripts, according to semiquantitative reverse transcription polymerase chain reaction analysis of PttGA20ox1, PttGA3ox1, and two putative PttGA2ox genes. We conclude that 20-oxidation is the limiting step, rather than 3b-hydroxylation, in the formation of GA 1 and GA 4 in elongating shoots of hybrid aspen, and that ectopic GA3ox expression alone cannot increase the flux toward bioactive GAs. Finally, several lines of evidence now suggest that GA 4 has a more pivotal role in the tree hybrid aspen than previously believed. Gibberellins (GAs) form a group of more than 130 tetracyclic diterpenes, some of which are biologically active and act as growth regulators in higher plants. Work on GA-deficient mutants has established that bioactive GAs play an important role in controlling diverse developmental processes such as seed germination, stem elongation, flowering, and fruit ripening (Davies, 1995). The GA biosynthetic pathway has been elucidated and its key components identified (for review, see Hedden and Phillips, 2000;Yamaguchi and Kamiya, 2000;Olszewski et al., 2002). The final steps in the pathway are catalyzed by the soluble 2-oxoglutarate-dependent dioxygenases GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox). The pathway branches at GA 12 , which can be 13-hydroxylated into GA 53 , marking the starting points for two parallel routes catalyzed by the above dioxygenases: the early nonhydroxylated and the 13-hydroxylated pathways forming the bioactive GAs, GA 4 and GA 1 , respectively. The multifunctional GA20ox removes a carbon by successive oxidation of GA 12 to GA 9 and GA 53 to GA 20 . However, the final interconversion into the bioactive GA 4 or GA 1 requires the action of the enzyme GA3ox. The deactivation of the bioactive species is catalyzed by GA2ox, which can also divert GA 9 and GA 20 away from the route toward...

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Section: Plant Transformation and Growth Conditionsmentioning

confidence: 99%

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

et al. 2004

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“…Regeneration and cultivation of hybrid aspen (Populus tremula L.iP. tremuloides Mich.) was according to Nilsson et al (1992) and Hampp et al (1996). Internodal segments 5 mm long were grown for 4 wk in Petri dishes on solid Murashige and Skoog (MS1) medium supplemented with 0.1 mg l −" indole-3-butyric acid, 0.2 mg l −" 6-benzylaminopurine (BAP), and 0.01 mg l −" Thidiazuron [1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea] (Sigma, Heidelberg, Germany).…”

Section: Plant Culturementioning

confidence: 99%

Mycorrhiza formation and elevated CO₂ both increase the capacity for sucrose synthesis in source leaves of spruce and aspen

et al. 2000

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The effects of mycorrhiza formation in combination with elevated CO # concentrations on carbon metabolism of Norway spruce (Picea abies) seedlings and aspen (Populus tremulaiPopulus tremuloides) plantlets were analysed. Plants were inoculated for 6 wk with the ectomycorrhizal fungi Amanita muscaria and Paxillus involutus (aspen only) in an axenic Petri-dish culture at 350 and 700 µl l −" CO # partial pressure. After mycorrhiza formation, a stimulation of net assimilation rate was accompanied by decreased activities of sucrose synthase, an increased activation state of sucrose-phosphate synthase, decreased fructose-2,6-bisphosphate and starch, and slightly elevated glucose-6-phosphate contents in source leaves of both host species, independent of CO # concentration. Exposure to elevated CO # generally resulted in higher net assimilation rates, increased starch as well as decreased fructose-2,6-bisphosphate (aspen only) content in source leaves of both mycorrhizal and nonmycorrhizal plants. Our data indicate only slightly improved carbon utilization by mycorrhizal plants at elevated CO # . They demonstrate however, that both factors which modulate the sink-source properties of plants increase the capacity for sucrose synthesis in source leaves mainly by allosteric enzyme regulation.

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“…The same plants that were used for hormone measurements were analyzed for their expression of the rolC gene in Williamson et al 1989;Nilsson et al, 1992). Thus, no selection for plants expressing the RolC protein to a lesser degree or in a different organ-specific manner has taken place during the regeneration procedure.…”

Section: Northern Analysis Of Transformed Plantsmentioning

confidence: 99%

Hormonal Characterization of Transgenic Tobacco Plants Expressing the rolC Gene of Agrobacterium rhizogenes TL-DNA

et al. 1993

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Spatial pattern of cauliflower mosaic virus 35S promoter-luciferase expression in transgenic hybrid aspen trees monitored by enzymatic assay and non-destructive imaging

Cited by 130 publications

References 46 publications

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

Mycorrhiza formation and elevated CO₂ both increase the capacity for sucrose synthesis in source leaves of spruce and aspen

Hormonal Characterization of Transgenic Tobacco Plants Expressing the rolC Gene of Agrobacterium rhizogenes TL-DNA

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Spatial pattern of cauliflower mosaic virus 35S promoter-luciferase expression in transgenic hybrid aspen trees monitored by enzymatic assay and non-destructive imaging

Cited by 130 publications

References 46 publications

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

Mycorrhiza formation and elevated CO2 both increase the capacity for sucrose synthesis in source leaves of spruce and aspen

Hormonal Characterization of Transgenic Tobacco Plants Expressing the rolC Gene of Agrobacterium rhizogenes TL-DNA

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Mycorrhiza formation and elevated CO₂ both increase the capacity for sucrose synthesis in source leaves of spruce and aspen