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Activity of the promoter of a nodule infected cell-specific gene, Cg164, from Casuarina glauca, in transgenic Lotus japonicus: is infected cell-specific transcription conserved between different root nodule symbioses?
Stockholm University, Faculty of Science, Department of Botany. (Katharina Pawlowski)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In order to examine the conservation of transcription factors in infected cells of nitrogen-fixing root nodules, the activity of promoter::reporter gene constructs was compared in transgenic hairy root systems of different root nodule forming plant species. The promoter under examination, Cg164, was taken from the Australian tree Casuarina glauca. Cg164 encodes a homologue of a nodule infected cell-specific gene family from the closely related actinorhizal tree Alnus glutinosa. After infection of Agrobacterium rhizogenes-induced transgenic hairy root systems of the model legume Lotus japonicus with Mesorhizobium loti strain TONO, the Cg164::GUS construct led to GUS activity in the roots, in the nodule outer cortex and in the nodule vascular system, but not in the infected cells of the nodules. Hence, the cell type-specificity of expression of Cg164 was not conserved. In order to find out which factors determined infected cell-specific expression, the effects of ROS and ethylene signaling on Cg164 promoter activity were examined. Ethylene signaling was required for the expression of Cg164::GUS, while salt stress, leading to ROS production, repressed Cg164 promoter activity.

URN: urn:nbn:se:su:diva-42405OAI: diva2:346016
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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