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Molecular analysis of transcription factors involved in Medicago truncatula nodulation

Katrien D'haeseleer UGent (2009)
abstract
Thanks to the symbiotic interaction with rhizobia many legumes are important natural fertilizers and pioneer plants on eroded soils. This plant-bacteria interaction leads to formation of root nodules in which differentiated rhizobia, alias bacteroids, fix nitrogen in return for C- and energy sources. Medicago truncatula and Lotus japonicus are considered as model legumes for the research on indeterminate en determinate nodule formation and development respectively. In chapter 1, an overview is given of the current knowledge on the nodulation process in model legumes, covering molecular players in nodule initiation and nitrogen fixation, description of the different stages of nodulation, involvement of hormones, autoregulation mechanisms and tools to study legumes. Based on the numerous transcription factors present in plant genomes, transcriptional gene regulation might constitute an important element to control plant processes including nodulation and identifying their role and target genes will help to elucidate complex gene networks. Within the nodulation process, several TFs were identified which regulate pathways leading to nodule formation and nodule functioning. In this study, the role of three transcription factors in nodulation and other plant developmental pathways was investigated in Medicago truncatula. In chapter 2 we focus on an AP2 domain containing transcription factor, MtRAP2.4, which was upregulated during nodule senescence and is a member of the DREB (dehydratation responsive elelement binding) subgroup of AP2 transcription factors. We performed an expression analysis, functional analysis and a micro-array analysis in order to define its role in the (later stages of the) nodulation process. Moreover, its role during nodulation in relation to stress is discussed. In chapter 3, the analysis of a basic leucine zipper (bZIP) transcription factor, MtATB2, is presented and discussed. Because this gene has a close homologue in A. thaliana from which the expression is strongly regulated by sucrose, we analyzed its expression not only during nodule senescence but also upon sucrose application. Moreover, the function of the gene is analyzed by modulating its expression level by ectopic expression and RNAi analysis. Whereas previous transcription factors were selected based on their upregulation in aging nodules, a third transcription factor, MtNAC1 was investigated based on its homology with AtNAC1 and the similarities between lateral root formation - in which AtNAC1 was involved - and nodule formation. The role of MtNAC1 in both processes is analyzed and discussed in chapter 4. Throughout this study, we frequently used the A. rhizogenes transformation method in order to obtain transgenic roots. Based on our experiences with this technique, we summarized tips and tricks in chapter 5 which might increase the efficiency of this transformation method.
Please use this url to cite or link to this publication:
author
promoter
UGent and UGent
organization
year
type
dissertation (monograph)
subject
pages
194 pages
publisher
Ghent University. Faculty of Sciences
place of publication
Ghent, Belgium
defense location
Zwijnaarde : Technologiepark (FSVM building)
defense date
2009-06-30 16:00
language
English
UGent publication?
yes
classification
D1
additional info
dissertation consists of copyrighed material
copyright statement
I have transferred the copyright for this publication to the publisher
id
3007408
handle
http://hdl.handle.net/1854/LU-3007408
date created
2012-10-05 11:43:12
date last changed
2012-10-08 11:04:41
@phdthesis{3007408,
  abstract     = {Thanks to the symbiotic interaction with rhizobia many legumes are important natural fertilizers and pioneer plants on eroded soils. This plant-bacteria interaction leads to formation of root nodules in which differentiated rhizobia, alias bacteroids, fix nitrogen in return for C- and energy sources. Medicago truncatula and Lotus japonicus are considered as model legumes for the research on indeterminate en determinate nodule formation and development respectively.
In chapter 1, an overview is given of the current knowledge on the nodulation process in model legumes, covering molecular players in nodule initiation and nitrogen fixation, description of the different stages of nodulation, involvement of hormones, autoregulation mechanisms and tools to study legumes. Based on the numerous transcription factors present in plant genomes, transcriptional gene regulation might constitute an important element to control plant processes including nodulation and identifying their role and target genes will help to elucidate complex gene networks. Within the nodulation process, several TFs were identified which regulate pathways leading to nodule formation and nodule functioning. In this study, the role of three transcription factors in nodulation and other plant developmental pathways was investigated in Medicago truncatula. In chapter 2 we focus on an AP2 domain containing transcription factor, MtRAP2.4, which was upregulated during nodule senescence and is a member of the DREB (dehydratation responsive elelement binding) subgroup of AP2 transcription factors. We performed an expression analysis, functional analysis and a micro-array analysis in order to define its role in the (later stages of the) nodulation process. Moreover, its role during nodulation in relation to stress is discussed. In chapter 3, the analysis of a basic leucine zipper (bZIP) transcription factor, MtATB2, is presented and discussed. Because this gene has a close homologue in A. thaliana from which the expression is strongly regulated by sucrose, we analyzed its expression not only during nodule senescence but also upon sucrose application. Moreover, the function of the gene is analyzed by modulating its expression level by ectopic expression and RNAi analysis. Whereas previous transcription factors were selected based on their upregulation in aging nodules, a third transcription factor, MtNAC1 was investigated based on its homology with AtNAC1 and the similarities between lateral root formation - in which AtNAC1 was involved - and nodule formation. The role of MtNAC1 in both processes is analyzed and discussed in chapter 4. Throughout this study, we frequently used the A. rhizogenes transformation method in order to obtain transgenic roots. Based on our experiences with this technique, we summarized tips and tricks in chapter 5 which might increase the efficiency of this transformation method.},
  author       = {D'haeseleer, Katrien},
  language     = {eng},
  pages        = {194},
  publisher    = {Ghent University. Faculty of Sciences},
  school       = {Ghent University},
  title        = {Molecular analysis of transcription factors involved in Medicago truncatula nodulation},
  year         = {2009},
}

Chicago
D’haeseleer, Katrien. 2009. “Molecular Analysis of Transcription Factors Involved in Medicago Truncatula Nodulation”. Ghent, Belgium: Ghent University. Faculty of Sciences.
APA
D’haeseleer, K. (2009). Molecular analysis of transcription factors involved in Medicago truncatula nodulation. Ghent University. Faculty of Sciences, Ghent, Belgium.
Vancouver
1.
D’haeseleer K. Molecular analysis of transcription factors involved in Medicago truncatula nodulation. [Ghent, Belgium]: Ghent University. Faculty of Sciences; 2009.
MLA
D’haeseleer, Katrien. “Molecular Analysis of Transcription Factors Involved in Medicago Truncatula Nodulation.” 2009 : n. pag. Print.