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ABSTRACT: In this paper we describe the identification of a gene, MsDWF1 coding for a putative gibberellin 3-beta-hydroxylase (GA3ox), whose natural mutation is conditioning a dwarf growth phenotype in Medicago sativa. The dwarf phenotype could not be complemented with grafting, which indicates that the bioactive gibberellin compound necessary for shoot elongation is immobile. On the contrary, exogenously added gibberellic acid restored normal growth. The genetic position of the Msdwf1 gene was mapped to linkage group 2 (LG2) and the physical location was delimited by map-based cloning using Medicago truncatula genomic resources. Based on the similar appearance and behavior of the dwarf Medicago sativa plants to the pea stem length mutant (le) as well as the synthenic map position of the two genes it was postulated that MsDWF1 and pea Le are orthologs. The comparison of wild type and mutant allele sequences of MsGA3ox revealed an amino acid change in a conserved position in the mutant allele, which most probably impaired the function of the enzyme. Our results indicate that the dwarf phenotype was the consequence of this mutation.
Plant Cell Reports 09/2008; 27(8):1271-9. · 2.27 Impact Factor
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Patrick H Middleton, Júlia Jakab,
R Varma Penmetsa,
Colby G Starker,
Jake Doll,
Péter Kaló,
Radhika Prabhu,
John F Marsh,
Raka M Mitra,
Attila Kereszt,
Brigitta Dudas,
Kathryn VandenBosch,
Sharon R Long,
Doug R Cook,
Gyorgy B Kiss,
Giles E D Oldroyd
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ABSTRACT: Rhizobial bacteria activate the formation of nodules on the appropriate host legume plant, and this requires the bacterial signaling molecule Nod factor. Perception of Nod factor in the plant leads to the activation of a number of rhizobial-induced genes. Putative transcriptional regulators in the GRAS family are known to function in Nod factor signaling, but these proteins have not been shown to be capable of direct DNA binding. Here, we identify an ERF transcription factor, ERF Required for Nodulation (ERN), which contains a highly conserved AP2 DNA binding domain, that is necessary for nodulation. Mutations in this gene block the initiation and development of rhizobial invasion structures, termed infection threads, and thus block nodule invasion by the bacteria. We show that ERN is necessary for Nod factor-induced gene expression and for spontaneous nodulation activated by the calcium- and calmodulin-dependent protein kinase, DMI3, which is a component of the Nod factor signaling pathway. We propose that ERN is a component of the Nod factor signal transduction pathway and functions downstream of DMI3 to activate nodulation gene expression.
The Plant Cell 05/2007; 19(4):1221-34. · 8.99 Impact Factor
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ABSTRACT: We have analysed the transposition and target selection strategy of IS1655, a typical IS30 family member resident in Neisseria meningitidis. We have redefined IS1655 as a 1080 bp long element with 25 bp imperfect inverted repeats (IRs), which generates a 3 bp target duplication and have shown that it transposes using an intermediate with abutted IRs separated by 2 bp. IS1655 exhibits bipartite target specificity inserting preferentially either next to sequences similar to its IRs or into an unrelated but well defined sequence. IR-targeting leads to the formation of a new junction in which the targeted IR and one of the donor IRs are separated by 2 bp. The non-IR targets were characterized as an imperfect 19 bp palindrome in which the central five positions show slight GC excess and the distal region is AT-rich. Artificial targets designed according to the consensus were recognized by the element as hot spots for insertion. The organization of IS1655 is similar to that of other IS30 family members. Moreover, it shows striking similarity to IS30 in transposition strategy even though their transposases differ in their N-terminal regions, which, for IS30, appears to determine target specificity. Comparative analysis of the transposases and the evolutionary aspects of sequence variants are also briefly discussed.
Molecular Microbiology 04/2007; 63(6):1731-47. · 5.01 Impact Factor
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Péter Kaló,
Cynthia Gleason,
Anne Edwards,
John Marsh,
Raka M Mitra,
Sibylle Hirsch, Júlia Jakab,
Sarah Sims,
Sharon R Long,
Jane Rogers,
György B Kiss,
J Allan Downie,
Giles E D Oldroyd
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ABSTRACT: Rhizobial bacteria enter a symbiotic interaction with legumes, activating diverse responses in roots through the lipochito oligosaccharide signaling molecule Nod factor. Here, we show that NSP2 from Medicago truncatula encodes a GRAS protein essential for Nod-factor signaling. NSP2 functions downstream of Nod-factor-induced calcium spiking and a calcium/calmodulin-dependent protein kinase. We show that NSP2-GFP expressed from a constitutive promoter is localized to the endoplasmic reticulum/nuclear envelope and relocalizes to the nucleus after Nod-factor elicitation. This work provides evidence that a GRAS protein transduces calcium signals in plants and provides a possible regulator of Nod-factor-inducible gene expression.
Science 07/2005; 308(5729):1786-9. · 31.20 Impact Factor
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ABSTRACT: A pályázat célja a Sinorhizobium meliloti és a Medicago truncatula között létrejövő szimbiotikus nitrogénkötő kapcsolat kialakításában résztvevő két M. truncatula gén (DMI1 és PDL) azonosítása volt. A mutánsok szimbiotikus fenotípusa azt valószínűsítette, hogy a mutációt szenvedett gének termékei a szimbiotikus gümő kialakulásának korai szakaszában, a bakteriális jelmolekula (Nod faktor) által elindított szignálútban, illetve a gümő organogenezisben vesznek részt. A gének azonosítását térképezésen alapuló génizolálással végeztük el, az izolált gének azonosságát pedig genetikai komplementációs kísérletekkel igazoltuk. Az DMI1 gén egy olyan fehérjét kódol, amely nem mutat hasonlóságot semmilyen eddig ismert növényi fehérjével, vagy annak alegységével. Tartalmaz viszont egy konzervativ domént, amely kisebb mértékű, de az egész doménre kiterjedő hasonlóságot mutatott bakteriális kálium csatornák TrkA doménjével, így a DMI1 fehérje feltételezhetően kation csatornaként, vagy annak alegységeként működik. A PDL gén klónozása során azonosítottunk egy AP2-típusú domént tartalmazó ERF típusú transzkripciós faktort kódoló gént, amely tartalmazott egy mutációt a pdl mutánsban. Együttműködő partnerünkkel bizonyítottuk a gén azonosságát és kimutattuk, hogy a gén szükséges a Nod faktor által indukált nodulin gén expresszióhoz, és meghatároztuk a Nod factor szignálútban elfoglalt helyét. | The aim of this project was to identify two Medicago truncatula genes, DMI1 and PDL which are required to establish symbiotic nitrogen fixing interaction between Sinorhizobium meliloti and M. truncatula. Based on the mutant phenotype, DMI1 and PDL were proposed to act in the Nod factor signal transduction pathway and revealed that the DMI protein is essential to enable mycorrhizal associations. The DMI1 and PDL genes were identified in cooperation with other laboratories by map-based cloning; that is ?chromosomal walking? starting from the closely linked molecular markers to the mutant genes were carried out. Transformation experiments were performed using the wild type genes to complement the mutant phenotypes genetically. The DMI1 gene encodes a protein with low global similarity to a ligand-gated cation channel domain of archaea. The pdl mutant was allelic to the bit1 mutant that shows a slightly different mutant phenotype and the two genes were renamed as ERN (ERF Required for Nodulation). ERN encodes a protein containing a highly conserved AP2 DNA binding domain. We identified the position of ERN in the Nod factor signal transduction pathway and showed that ERN is necessary for Nod factor?induced gene expression.
