Péter Putnoky
Hungarian Academy of Sciences
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Péter Putnoky.
Molecular Microbiology | 1998
Péter Putnoky; Attila Kereszt; Tatsunosuke Nakamura; Gabriella Endre; Erich Grosskopf; Peter Kiss; Adam Kondorosi
The fix‐2 mutant of Rhizobium meliloti affected in the invasion of alfalfa root nodules (Inf−/Fix−) is K+ sensitive and unable to adapt to alkaline pH in the presence of K+. Using directed Tn5 mutagenesis, we delimited a 6 kb genomic region in which mutations resulted in both Inf−/Fix− and K+‐sensitive phenotypes. In this DNA region, seven open reading frames (ORFs) were identified and the corresponding genes were designated phaA, B, C, D, E, F and G. The putative PhaABC proteins exhibit homology to the subunits of a Na+/H+ antiporter from an alkalophilic Bacillus strain. Moreover, PhaA and PhaD also show similarity to the ND5 and ND4 subunits of the proton‐pumping NADH:ubiquinone oxidoreductase respectively. Computer analysis suggests that all seven proteins are highly hydrophobic with several possible transmembrane domains. Some of these domains were confirmed by generating active alkaline phosphatase fusions. Ion transport studies on phaA mutant cells revealed a defect in K+ efflux at alkaline pH after the addition of a membrane‐permeable amine. These results suggest that the pha genes of R. meliloti encode for a novel type of K+ efflux system that is involved in pH adaptation and is required for the adaptation to the altered environment inside the plant.
Journal of Molecular Biology | 1986
Michael Göttfert; Beatrix Horvath; Eva Kondorosi; Péter Putnoky; Francisco Rodriguez-Quiñones; Adam Kondorosi
A Rhizobium meliloti DNA region (nodD1) involved in the regulation of other early nodulation genes has been delimited by directed Tn5 mutagenesis and its nucleotide sequence has been determined. The sequence data indicate a large open reading frame with opposite polarity to nodA, -B and -C, coding for a protein of 308 (or 311) amino acid residues. Tn5 insertion within the gene caused a delay in nodulation of Medicago sativa from four to seven days. Hybridization of nodD1 to total DNA of Rhizobium meliloti revealed two additional nodD sequences (nodD2 and nodD3) and both were localized on the megaplasmid pRme41b in the vicinity of the other nod genes. Genetic and DNA hybridization data, combined with nucleotide sequencing showed that nodD2 is a functional gene, while requirement of nodD3 for efficient nodulation of M. sativa could not be detected under our experimental conditions. The nodD2 gene product consists of 310 amino acid residues and shares 86.4% homology with the nodD1 protein. Single nodD2 mutants had the same nodulation phenotype as the nodD1 mutants, while a double nodD1-nodD2 mutant exhibited a more severe delay in nodulation. These results indicate that at least two functional copies of the regulatory gene nodD are necessary for the optimal expression of nodulation genes in R. meliloti.
Molecular Microbiology | 1993
György Petrovics; Péter Putnoky; Bradley L. Reuhs; John S. Kim; Tina A. Thorp; K. Dale Noel; Russell W. Carlson; Adam Kondorosi
Bacterial exopolysaccharide (EPS) and lipopolysaccharide (LPS) molecules have been shown to play important roles in plant‐bacterium interactions. Here we have demonstrated that the fix‐23 loci, which compensate for exo mutations during symbiotic nodule development, are involved in the production of a novel polysaccharide that is rich in 3‐deoxy‐D manno‐2‐octulosonic acid (Kdo) but is not the classical LPS. This molecule is likely to be a surface antigen since antiserum to whole Rhizobium meliloti cells reacts strongly with it, and since mutations in fix‐23 result in an inability to produce this polysaccharide and to bind bacteriophage 16‐3. It is likely that this Kdo‐rich polysaccharide is analogous to certain Escherichia coli K‐antigens which are anchored to the membrane via a phospholipid moiety. DNA sequence analysis of one gene cluster of this region revealed that the predicted protein products of six genes exhibit a high degree of homology and similar organization to those of the rat fatty acid synthase multifunctional enzyme domains.
Molecular Genetics and Genomics | 1983
Péter Putnoky; György B. Kiss; István Ott; Adam Kondorosi
SummaryIn Rhizobium meliloti, Tn5 conferred resistance not only to kanamycin but to streptomycin, as well, in Escherichia coli, however only to kanamycin. Using in vitro recombinant DNA techniques, it was shown that the streptomycin resistance determinant was located downstream from the kanamycin resistance gene in the unique central region of Tn5. Expression of various cloned fragments of Tn5 suggested that both kanamycin and streptomycin resistance genes were transcribed from the same promoter. E. coli mutants allowing the expression of streptomycin resistance from Tn5 were isolated. The differential expression of the streptomycin resistance gene provides a simple selection/counterselection criterion, using only streptomycin in transfer expriments of Tn5 between E. coli and R. meliloti.
Molecular Genetics and Genomics | 1995
Attila Kereszt; Krystyna Slaska-Kiss; Péter Putnoky; Zsofia Banfalvi; Adam Kondorosi
We report the genetic and biochemical analysis of Rhizobium meliloti mutants defective in symbiotic nitrogen fixation (Fix−) and “respiratory” nitrate reduction (Rnr−). The mutations were mapped close to the ade-1 and cys-46 chromosomal markers and the mutated locus proved to be identical to the previously described fix-14 locus. By directed Tn5 mutagenesis, a 4.5 kb segment of the chromosome was delimited in which all mutations resulted in Rnr− and Fix− phenotypes. Nucleotide sequence analysis of this region revealed the presence of four open reading frames coding for integral membrane and membrane-anchored proteins. Biochemical analysis of the mutants showed that the four proteins were necessary for the biogenesis of all cellular c-type cytochromes. In agreement with the nomenclature proposed for rhizobial genes involved in the formation of c-type cytochromes, the four genes were designated cycH, cycJ, cycK, and cycL, respectively. The predicted protein product of cycH exhibited a high degree of similarity to the Bradyrhizobium japonicum counterpart, while CycK and CycL shared more than 50% amino acid sequence identity with the Rhodobacter capsulatus Ccll and Cc12 proteins, respectively. cycJ encodes a novel membrane anchored protein of 150 amino acids. We suggest that this gene cluster codes for (parts of) a multi-subunit cytochrome c haem lyase. Moreover, our results indicate that in R. meliloti c-type cytochromes are required for respiratory nitrate reduction ex planta, as well as for symbiotic nitrogen fixation in root nodules.
Molecular Plant-microbe Interactions | 2001
Ernő Kiss; Attila Kereszt; Fatime Barta; Samuel B. Stephens; Bradley L. Reuhs; Adam Kondorosi; Péter Putnoky
The rkp-3 region is indispensable for capsular polysaccharide (K antigen) synthesis in Sinorhizobium meliloti Rm41. Strain Rm41 produces a K antigen of strain-specific structure, designated as the KR5 antigen. The data in this report show that the rkp-3 gene region comprises 10 open reading frames involved in bacterial polysaccharide synthesis and export. The predicted amino acid sequences for the rkpL-Q gene products are homologous to enzymes involved in the production of specific sugar moieties, while the putative products of the rkpRST genes show a high degree of similarity to proteins required for transporting polysaccharides to the cell surface. Southern analysis experiments using gene-specific probes suggest that genes involved in the synthesis of the precursor sugars are unique in strain Rm41, whereas sequences coding for export proteins are widely distributed among Sinorhizobium species. Mutations in the rkpL-Q genes result in a modified K antigen pattern and impaired symbiotic capabilities. On this basis, we suggest that these genes are required for the production of the KR5 antigen that is necessary for S. meliloti Rm41 exoB (AK631)-alfalfa (Medicago sativa) symbiosis.
Archive | 1985
Adam Kondorosi; Beatrix Horvath; Michael Göttfert; Péter Putnoky; Katalin Rostás; Zoltan Györgypal; Eva Kondorosi; I. Török; Christian W. B. Bachem; Michael John; Jürgen Schmidt; Jeff Schell
The bacterium species Rhizobium meliloti induces nitrogen fixing nodules on the roots of its host plant Medicago sativa (alfalfa). The majority of symbiotic genes of R. meliloti are located on a megaplasmid, including genes coding for early functions in nodulation (nod), the nitrogenase genes (nif) and other genes required for nitrogen fixation (fix) (Banfalvi et al. 1981; Rosenberg et al. 1981). When this megaplasmid was transferred into other Rhizobium species or into Agrobacterium tumefaciens, these latter bacteria became able to induce ineffective nodules on alfalfa, indicating that the essential genes coding for nodule initiation and development are carried by this megaplasmid (Kondorosi et al. 1982). The development of these nodules, however, halted at an early stage: infection threads did not form and neither bacteria nor bacteroids were found in the inner nodule tissue (Wong et al. 1983).
Molecular Plant-microbe Interactions | 2009
Adrienn Pálvölgyi; Veronika Deák; Véréna Poinsot; Tibor Nagy; Enik Nagy; Ildikó Kerepesi; Péter Putnoky
Rhizobial surface polysaccharides, including capsular polysaccharides (KPS), are involved in symbiotic infection. The rkp-3 locus of Sinorhizobium meliloti 41 is responsible for the production of pseudaminic acid, one of the components of the KR5 antigen, a strain-specific KPS. We have extended the sequence determination and genetic dissection of the rkp-3 region to clarify the structure and function of the rkpY gene and to identify additional rkp genes. Except for rkpY, no other genes were found where mutation affected the KPS structure and symbiosis. These mutants show a unique phenotype producing a low molecular weight polysaccharide (LMW PS). Creating double mutants, we have shown that biosynthesis genes of the KR5 antigen except rkpZ are not necessary for the production of this LMW PS. Polysaccharide analysis of genetically modified strains suggests that rkpY has pleiotropic effects on polysaccharide production. It directs KPS synthesis to the KR5 antigen and influences lipo-oligo 3-deoxy-d-manno-2 octulosonic acid (Kdo) production in S. meliloti 41. In addition, rkpY suppresses the lipo-oligoKdo production when it is introduced into S. meliloti 1021.
Molecular Genetics and Genomics | 1989
Zsófia Bánfalvi; V. Petkova; M. Lados; Krystyna Slaska-Kiss; Péter Putnoky; C. H. Ung; Adam Kondorosi
SummaryRecently, Fix- mutants of Rhizobium meliloti 41 defective for nifHDK transcription in the bacteroid state have been described. Two of these mutants have been used to identify bacterial genes involved in the regulation of nif gene expression. A nifA::lacZ fusion was introduced into the mutant strains and β-galactosidase activity was assayed in nodule bacteria, as well as in bacteria grown under microaerobic conditions. One of the mutants did not express the nifA gene in symbiosis, suggesting that the gene inactivated by mutation fix-24 is involved in controlling the expression of the nif structural genes via the regulatory gene nifA, The mutation fix-24 also impaired the expression of nifA under microaerobic conditions. These data are in agreement with earlier findings that low oxygen concentration may serve as a signal for nif gene expression in symbiosis. The fix gene marked by the mutation fix-24 might be a positive regulator of nifA expression in R. meliloti 41. The other mutation (fix-25) represented another cluster of fix genes which also affected the expression of nifA. This influence, however, was specific for symbisis. The fix genes (fix-24, fix-25) were localized on the symbiotic megaplasmid pRme41b. The two genes are 10 kb apart from each other and are located at 200 kb downstream of the nif structural genes in R. meliloti 41.
Genes & Development | 1998
Kinga Németh; Klaus Salchert; Péter Putnoky; Rishikesh P. Bhalerao; Zsuzsanna Koncz-Kálmán; Biljana Stankovic-Stangeland; László Bakó; Jaideep Mathur; László Ökrész; Sylvia Stabel; Peter Geigenberger; Mark Stitt; George P. Rédei; Jeff Schell; Csaba Koncz