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The role of CLE peptides during nodulation

(2011)
Author
Promoter
(UGent) and (UGent)
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Abstract
Legumes develop root nodules as a result of a symbiotic interaction with soil borne bacteria, called rhizobia. Inside the nodules the bacteria find the ideal niche to fix atmospheric nitrogen for the plant in return for energy sources. Nodule formation is a complex developmental process that requires the spatio-temporal expression of plant and bacterial genes. Nodulation can be divided in two developmental pathways, bacterial infection and organ initiation, and the two merge when the bacteria are taken up by the plant cells. Two types of nodules have been characterized, determinate nodules such as originating on soybean (Glycine max) and indeterminate nodules such as observed on Medicago truncatula. Determinate nodules are round-shaped and terminally differentiated, while indeterminate nodules have a persistent apical meristem. Nodule organogenesis is governed by the bacterially produced Nod factors and downstream of it, cytokinin signaling. As nodulation is an energy-consuming process, legumes developed long distance mechanisms to control nodule number, amongst which autoregulation of nodulation (AON), involving reciprocal signal exchange between the root system and the shoot. Here, we have shown that structurally related CLE peptides play a main role during several aspects of M. truncatula nodulation. During nodulation, CLE peptide genes are activated downstream of the Nod factor and cytokinin signaling cascade and control the balance between cell division and differentiation. In addition, we show that CLE peptides control nodule numbers by interacting with the AON pathway. Although the underlying mechanism of this interaction is not yet resolved, our results opened new possibilities to explain the AON pathway. In addition, genes were identified that might be involved in the CLE peptide dependent negative feedback mechanism that controls nodule number. Especially the downregulation of a NF receptor gene is an interesting finding. In parallel, we also found nodulation-related CLE peptide genes that might control determinate nodulation in soybean. Moreover, we identified putative receptors of nodulation-related CLE peptides in the genomes of M. truncatula and G. max. Finally, our results indicate that de novo cytokinin activation via a cytokinin riboside 5’-monophosphate phosphoribohydrolase LONELY GUY1 of M. truncatula is needed for normal nodule development and possibly involves CLE signaling.
Keywords
Medicago truncatula, CLE, nodulation, soybean, lonely guy, SUNN

Citation

Please use this url to cite or link to this publication:

Chicago
Mortier, Virginie. 2011. “The Role of CLE Peptides During Nodulation”. Ghent, Belgium: Ghent University. Faculty of Sciences.
APA
Mortier, V. (2011). The role of CLE peptides during nodulation. Ghent University. Faculty of Sciences, Ghent, Belgium.
Vancouver
1.
Mortier V. The role of CLE peptides during nodulation. [Ghent, Belgium]: Ghent University. Faculty of Sciences; 2011.
MLA
Mortier, Virginie. “The Role of CLE Peptides During Nodulation.” 2011 : n. pag. Print.
@phdthesis{1234605,
  abstract     = {Legumes develop root nodules as a result of a symbiotic interaction with soil borne bacteria, called rhizobia. Inside the nodules the bacteria find the ideal niche to fix atmospheric nitrogen for the plant in return for energy sources. Nodule formation is a complex developmental process that requires the spatio-temporal expression of plant and bacterial genes. Nodulation can be divided in two developmental pathways, bacterial infection and organ initiation, and the two merge when the bacteria are taken up by the plant cells. Two types of nodules have been characterized, determinate nodules such as originating on soybean (Glycine max) and indeterminate nodules such as observed on Medicago truncatula. Determinate nodules are round-shaped and terminally differentiated, while indeterminate nodules have a persistent apical meristem. Nodule organogenesis is governed by the bacterially produced Nod factors and downstream of it, cytokinin signaling. As nodulation is an energy-consuming process, legumes developed long distance mechanisms to control nodule number, amongst which autoregulation of nodulation (AON), involving reciprocal signal exchange between the root system and the shoot.
Here, we have shown that structurally related CLE peptides play a main role during several aspects of M. truncatula nodulation. During nodulation, CLE peptide genes are activated downstream of the Nod factor and cytokinin signaling cascade and control the balance between cell division and differentiation. In addition, we show that CLE peptides control nodule numbers by interacting with the AON pathway. Although the underlying mechanism of this interaction is not yet resolved, our results opened new possibilities to explain the AON pathway. In addition, genes were identified that might be involved in the CLE peptide dependent negative feedback mechanism that controls nodule number. Especially the downregulation of a NF receptor gene is an interesting finding. In parallel, we also found nodulation-related CLE peptide genes that might control determinate nodulation in soybean. Moreover, we identified putative receptors of nodulation-related CLE peptides in the genomes of M. truncatula and G. max. Finally, our results indicate that de novo cytokinin activation via a cytokinin riboside 5{\textquoteright}-monophosphate phosphoribohydrolase LONELY GUY1 of M. truncatula is needed for normal nodule development and possibly involves CLE signaling.},
  author       = {Mortier, Virginie},
  keyword      = {Medicago truncatula,CLE,nodulation,soybean,lonely guy,SUNN},
  language     = {eng},
  pages        = {XVII, 323},
  publisher    = {Ghent University. Faculty of Sciences},
  school       = {Ghent University},
  title        = {The role of CLE peptides during nodulation},
  year         = {2011},
}