| 1. |
- Eriksson, Maria E., et al.
(författare)
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Transgenic hybrid aspen trees with increased gibberellin (GA) concentrations suggest that GA acts in parallel with FLOWERING LOCUS T2 to control shoot elongation
- 2015
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 205:3, s. 1288-1295
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Tidskriftsartikel (refereegranskat)abstract
- Bioactive gibberellins (GAs) have been implicated in short day (SD)-induced growth cessation in Populus, because exogenous applications of bioactive GAs to hybrid aspens (Populus tremulaxtremuloides) under SD conditions delay growth cessation. However, this effect diminishes with time, suggesting that plants may cease growth following exposure to SDs due to a reduction in sensitivity to GAs.In order to validate and further explore the role of GAs in growth cessation, we perturbed GA biosynthesis or signalling in hybrid aspen plants by overexpressing AtGA20ox1, AtGA2ox2 and PttGID1.3 (encoding GA biosynthesis enzymes and a GA receptor).We found trees with elevated concentrations of bioactive GA, due to overexpression of AtGA20ox1, continued to grow in SD conditions and were insensitive to the level of FLOWERING LOCUS T2 (FT2) expression. As transgenic plants overexpressing the PttGID1.3 GA receptor responded in a wild-type (WT) manner to SD conditions, this insensitivity did not result from limited receptor availability.As high concentrations of bioactive GA during SD conditions were sufficient to sustain shoot elongation growth in hybrid aspen trees, independent of FT2 expression levels, we conclude elongation growth in trees is regulated by both GA- and long day-responsive pathways, similar to the regulation of flowering in Arabidopsis thaliana.
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| 2. |
- Guenin, Stephanie, et al.
(författare)
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Normalization of qRT-PCR data : the necessity of adopting a systematic, experimental conditions-specific, validation of references
- 2009
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 60:2, s. 487-493
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative RT-PCR (reverse transcription polymerase chain reaction, also known as qRT-PCR or real-time RT-PCR) has been used in large proportions of transcriptome analyses published to date. The accuracy of the results obtained by this method strongly depends on accurate transcript normalization using stably expressed genes, known as references. Statistical algorithms have been developed recently to help validate reference genes but, surprisingly, this robust approach is under-utilized in plants. Instead, putative ’housekeeping’ genes tend to be used as references without any proper validation. The concept of normalization in transcript quantification is introduced here and the factors affecting its reliability in qRT-PCR are discussed in an attempt to convince molecular biologists, and non-specialists, that systematic validation of reference genes is essential for producing accurate, reliable data in qRT-PCR analyses, and thus should be an integral component of them.
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| 3. |
- Gutierrez, Laurent, et al.
(författare)
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The lack of a systematic validation of reference genes : a serious pitfall undervalued in reverse transcription-polymerase chain reaction (RT-PCR) analysis in plants.
- 2008
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Ingår i: Plant Biotechnology Journal. - : Wiley. - 1467-7644 .- 1467-7652. ; 6:6
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Tidskriftsartikel (refereegranskat)abstract
- Reverse transcription-polymerase chain reaction (RT-PCR) approaches have been used in a large proportion of transcriptome analyses published to date. The accuracy of the results obtained by this method strongly depends on accurate transcript normalization using stably expressed genes, known as references. Statistical algorithms have been developed recently to help validate reference genes, and most studies of gene expression in mammals, yeast and bacteria now include such validation. Surprisingly, this important approach is under-utilized in plant studies, where putative housekeeping genes tend to be used as references without any appropriate validation. Using quantitative RT-PCR, the expression stability of several genes commonly used as references was tested in various tissues of Arabidopsis thaliana and hybrid aspen (Populus tremula x Populus tremuloides). It was found that the expression of most of these genes was unstable, indicating that their use as references is inappropriate. The major impact of the use of such inappropriate references on the results obtained by RT-PCR is demonstrated in this study. Using aspen as a model, evidence is presented indicating that no gene can act as a universal reference, implying the need for a systematic validation of reference genes. For the first time, the extent to which the lack of a systematic validation of reference genes is a stumbling block to the reliability of results obtained by RT-PCR in plants is clearly shown.
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| 6. |
- Mauriat, Melanie, et al.
(författare)
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Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport
- 2014
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Ingår i: The Plant Journal. - : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 78:3, s. 372-384
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula x tremuloides) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis.
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| 7. |
- Mauriat, Melanie, et al.
(författare)
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Proper gibberellin localization in vascular tissue is required to control auxin-dependent leaf development and bud outgrowth in hybrid aspen
- 2011
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Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 67, s. 805-816
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Tidskriftsartikel (refereegranskat)abstract
- Bioactive gibberellins (GAs) are involved in many developmental aspects in the life cycle of plants, acting either directly or through interaction with other hormones. One way to study the role of GA in specific mechanisms is to modify the levels of bioactive GA in specific tissues. We increased GA catabolism in different parts of the vascular tissue by overexpressing two different GA 2-oxidase genes that encode oxidases with affinity for C(20)- or C(19)-GA. We show that, irrespective of their localization in the vascular tissue, the expression of different members of this gene family leads to similar modifications in the primary and secondary growth of the stem of hybrid aspen. We also show that the precise localization of bioactive GA downregulation is important for the proper control of other developmental aspects, namely leaf shape and bud dormancy. Expression under the control of one of the studied promoters significantly affected both the shape of the leaves and the number of sylleptic branches. These phenotypic defects were correlated with alterations in the levels and repartitioning of auxins. We conclude that a precise localization of bioactive GA in the vasculature of the apex is necessary for the normal development of the plant through the effect of GAs on auxin transport.
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