title: Crosstalk between the nodulation signaling pathway and the autoregulation of nodulation in Medicago truncatula.
abstract: A subset of CLAVATA3/endosperm-surrounding region-related (CLE) peptides are involved in autoregulation of nodulation (AON) in Medicago truncatula (e.g. MtCLE12 and MtCLE13). However, their linkage to other components of the AON pathways downstream of the shoot-derived inhibitor (SDI) is not understood. We have ectopically expressed the putative peptide ligand encoding genes MtCLE12 and MtCLE13 in M. truncatula which abolished nodulation completely in wild-type roots but not in the supernodulating null mutant sunn-4. Further, root growth inhibition was detected when MtCLE12 was ectopically expressed in wild-type roots or synthetic CLE12 peptide was applied exogenously. To identify downstream genes, roots of wild-type and sunn-4 mutant overexpressing MtCLE12 were used for quantitative gene expression analysis. We found that, in 35S:MtCLE12 roots, NODULE INCEPTION (NIN, a central regulator of nodulation) was down-regulated, whereas MtEFD (ethylene response factor required for nodule differentiation) and MtRR8 (a type-A response regulator thought to be involved in the negative regulation of cytokinin signaling), were up-regulated. Moreover, we found that the up-regulation of MtEFD and MtRR8 caused by overexpressing MtCLE12 is SUNN-dependent. Hence, our data link for the first time the pathways for Nod factor signaling, cytokinin perception and AON.
authors.affiliation: Australian Research Council Centre of Excellence for Integrative Legume Research, Plant Science Division, Research School of Biology, The Australian National University, Canberra 0200, Australia.
authors.forename: Isabel M L
authors.initials: IML
authors.lastname: Saur
authors.affiliation: Australian Research Council Centre of Excellence for Integrative Legume Research, Plant Science Division, Research School of Biology, The Australian National University, Canberra 0200, Australia.
authors.forename: Marie
authors.initials: M
authors.lastname: Oakes
authors.affiliation: Australian Research Council Centre of Excellence for Integrative Legume Research, Plant Science Division, Research School of Biology, The Australian National University, Canberra 0200, Australia.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Djordjevic
authors.affiliation: Australian Research Council Centre of Excellence for Integrative Legume Research, Plant Science Division, Research School of Biology, The Australian National University, Canberra 0200, Australia.
authors.forename: Nijat
authors.initials: N
authors.lastname: Imin
mesh_terms: D018506:Gene Expression Regulation, Plant; D005822:Genetic Vectors; D046913:Medicago truncatula / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D008958:Models, Molecular; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D055170:Plant Root Nodulation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D053204:Root Nodules, Plant / Q000235:genetics / Q000254:growth & development* / Q000382:microbiology; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000254:growth & development
chemical_list: D010940:Plant Proteins; D011993:Recombinant Fusion Proteins