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The Casuarina glauca metallothionein I promoter in transgenic nodulated hairy roots of the actinorhizal plant Datisca glomerata and the legume Lotus japonicus: auxin and cytokinin affect promoter activity
Stockholm University, Faculty of Science, Department of Botany. (Katharina Pawlowski)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In the past, the activity of the promoter of a metallothionein gene expressed in actinorhizal nodules of Casuarina glauca, CgMT1, has been analysed in Casaurinaceae and in tobacco, Arabidopsis and rice. In all these plants, the promoter showed high activity in the root cortex and –epidermis, making it a useful tool for the expression of transgenes. Therefore, its activity was now analysed in transgenic root systems of Datisca glomerata, an actinorhizal plant from a different phylogenetic group than C. glauca, using the same CgMT1::GUS fusion as in previous studies. However, in contrast with all other plant species examined previously, the CgMT1::GUS construct showed no activity at all in D. glomerata hairy roots, while the expression pattern in nodules resembled that found in C. glauca nodules. This is probably due to the changed hormone balance in hairy roots since experiments on the CgMT1::GUS construct in transgenic Arabidopsis showed that CgMT1 promoter activity was repressed by auxin or cytokinin, respectively. Yet, in hairy roots of the model legume Lotus japonicus induced by the same Agrobacterium rhizogenes strain, the CgMT1 promoter was active in roots and not in nodules, indicating that while pRi T-DNA genes lead to a changed hormone balance, the changes do not abolish the differences in phytorhomone levels/-sensitivity between plant species.


URN: urn:nbn:se:su:diva-42406OAI: diva2:346018
Available from: 2010-08-30 Created: 2010-08-30 Last updated: 2010-08-30Bibliographically approved
In thesis
1. Conservation of transcription factors in infected cells of nitrogen-fixing root nodules
Open this publication in new window or tab >>Conservation of transcription factors in infected cells of nitrogen-fixing root nodules
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Infected cells of nitrogen-fixing root nodules are the only plant cells that can stably internally accommodate a eubacterial symbiont. In the context of studying the differentiation of infected cells, we set about to analyse the conservation of infected cell-specific transcription factors using altogether four different promoters from genes showing infected cell-specific expression, or nodule-specific expression. The activity of promoter-reporter gene constructs was compared in transgenic hairy root systems of three different root nodule-forming plant species. The model species were two actinorhizal plants; the tree Casuarina glauca and the riparian weed Datisca glomerata, and the model legume Lotus japonicus. C. glauca and D. glomerata belong to different phylogenetic subgroups (Fagales vs. Cucurbitales) of actinorhizal plants showing strong differences with regard to nodule morphology, -metabolism and infection mechanism.

The results indicate one type of infected cell-specific transcription factors previously shown to be conserved between legumes and C. glauca is also conserved in D. glomerata. However, another type of transcription factor specific to infection thread-containing cells of C. glauca and the model legume Medicago truncatula is not conserved in D. glomerata. These results indicate that in this group of actinorhizal plants, infection thread growth occurs via a different mechanism, a conclusion supported by cytological analysis.

Furthermore, the results indicate that gene expression in infected cells of root nodules can be achieved by control mechanisms other than cell type-specific transcription factors, and that in this context, phytohormone regulation deserves further study.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2010. 69 p.
root nodules, actinorhiza, legumes, infection thread, Frankia, subtilase, leghemoglobin, chitinase
National Category
Research subject
Plant Physiology
urn:nbn:se:su:diva-42389 (URN)978-91-7447-140-3 (ISBN)
Public defence
2010-10-08, Föresläsningssalen Botanicum, Lilla Frescativägen 5, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-09-16 Created: 2010-08-27 Last updated: 2010-08-30Bibliographically approved

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Rashidi, Behnoosh
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