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G Endre

Publications and source records attributed to G Endre.

9 recordsLinked to original sources
PubMed2004

Comparative mapping between Medicago sativa and Pisum sativum.

Comparative genome analysis has been performed between alfalfa (Medicago sativa) and pea (Pisum sativum), species which represent two closely related tribes of the subfamily Papilionoideae with different basic chromosome numbers. The positions of genes on the most recent linkage map of diploid alfalfa were compared to those of homologous loci on the combined genetic map of pea to analyze the degree of co-linearity between their linkage groups. In addition to using unique genes, analysis of the map positions of multicopy (homologous) genes identified syntenic homologs (characterized by similar positions on the maps) and pinpointed the positions of non-syntenic homologs. The comparison revealed extensive conservation of gene order between alfalfa and pea. However, genetic rearrangements (due to breakage and reunion) were localized which can account for the difference in chromosome number (8 for alfalfa and 7 for pea). Based on these genetic events and our increasing knowledge of the genomic structure of pea, it was concluded that the difference in genome size between the two species (the pea genome is 5- to 10-fold larger than that of alfalfa) is not a consequence of genome duplication in pea. The high degree of synteny observed between pea and Medicago loci makes further map-based cloning of pea genes based on the genome resources now available for M. truncatula a promising strategy.

Base Sequence↗
PubMed2002

Genetic mapping of the non-nodulation phenotype of the mutant MN-1008 in tetraploid alfalfa (Medicago sativa).

Abstract. Roots of the non-nodulating Medicago sativa mutant MN-1008 neither undergo root-hair curling, cortical cell division nor any of the early molecular events that accompany nodule initiation and development following rhizobial infection or treatment with Nod factor. These observations suggested that the mutation(s) impaired a pivotal function in Nod factor perception or in the signal transduction pathway. In this paper we show that the genetic lesion conditioning the recessive non-nodulation phenotype in the tetraploid alfalfa mutant MN-1008 can be localized to a single region on LG5 of the M. sativa genetic map. This conclusion is based on genetic analyses conducted at the tetraploid level, involving both segregation analysis and genetic mapping of the trait with respect to molecular DNA markers. The genetic mapping of the Nod(-) phenotype was performed in a segregating tetraploid F2 population, taking advantage of the availability of an advanced genetic map for diploid alfalfa. Two tightly linked flanking markers have been identified which will facilitate the physical mapping and cloning of the gene(s) that underlie(s) the non-nodulation phenotype.

Chromosome Mapping↗
PubMed2000

Nuclear localization of a hypoxia-inducible novel non-symbiotic hemoglobin in cultured alfalfa cells.

We have isolated a 483-bp-long full-length cDNA clone encoding a non-symbiotic hemoglobin called Mhb1, the first one found in alfalfa. This non-symbiotic hemoglobin is a single copy gene localized in linkage group 4 in diploid Medicago genome. The Mhb1 mRNA was found only in the roots of alfalfa plants. The Mhb1 gene was inducible by hypoxia and showed no induction by cold stress treatment. The Mhb1 transcript level increased at the G2/M boundary in a synchronized alfalfa cell suspension culture. The majority of Mhb1 protein was shown to be localized in the nucleus and smaller amounts were detected in the cytoplasm. A potential link to the nitric oxide signalling pathway is also discussed.

Amino Acid Sequence↗
PubMed1998

The pha gene cluster of Rhizobium meliloti involved in pH adaptation and symbiosis encodes a novel type of K+ efflux system.

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 6kb 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.

Adaptation, Physiological↗
PubMed1994

ENOD12, an early nodulin gene, is not required for nodule formation and efficient nitrogen fixation in alfalfa.

To demonstrate the importance of an extensively studied early nodulin gene ENOD12 in symbiotic nodule development, plants of different Medicago sativa subspecies were tested for the presence or absence of ENOD12 alleles. In M. s. ssp coerulea w2 (Mcw2), two ENOD12 genes were detected, whereas in M. s. ssp quasifalcata k93 (Mqk93) only one gene was present. In both plants, the ENOD12 genes were expressed in nodules induced by Rhizobium meliloti. The nucleotide sequence of the ENOD12 genes showed that the two Mcw2-specific genes were similar to the ENOD12A and ENOD12B genes of the tetraploid M. s. ssp sativa. ENOD12 from Mqk93 was similar to the corresponding gene found in M. truncatula. From the aligned ENOD12 sequences, an evolutionary tree was constructed. Genetic analysis of the progenies of a cross between Mqk93 and Mcw2 showed that several offspring in F1 carried a null allele originating from Mcw2, and among the F2 progenies, plants with the null allele only lacking the ENOD12 gene appeared. Surprisingly, the ENOD12-deficient plants were similar to their wild-type parents in viability, nodule development, nodule structure, and nitrogen fixation efficiency. Therefore, we concluded that in Medicago the ENOD12 gene is not required for symbiotic nitrogen fixation. Furthermore, we proposed that the heterozygous nature of these legumes can be exploited for the identification of mutated alleles of other known nodulin genes; this will permit the construction of plant mutants deficient in these genes.

Alleles↗
PubMed1992

Rhizobium meliloti produces a family of sulfated lipooligosaccharides exhibiting different degrees of plant host specificity.

We have shown that a Rhizobium meliloti strain overexpressing nodulation genes excreted high amounts of a family of N-acylated and 6-O-sulfated N-acetyl-beta-1,4-D-glucosamine penta-, tetra-, and trisaccharide Nod factors. Either a C(16:2) or a C(16:3) acyl chain is attached to the nonreducing end subunit, whereas the sulfate group is bound to the reducing glucosamine. One of the tetrasaccharides is identical to the previously described NodRm-1 factor. The two pentasaccharides as well as NodRm-1 were purified and tested for biological activity. In the root hair deformation assay the pentasaccharides show similar activities on the host plants Medicago sativa and Melilotus albus and on the non-host plant Vicia sativa at a dilution of up to 0.01-0.001 microM, in contrast to NodRm-1, which displays a much higher specific activity for Medicago and Melilotus than for Vicia. The active concentration range of the pentasaccharides is more narrow on Medicago than on Melilotus and Vicia. In addition to root hair deformation, the different Nod factors were shown to induce nodule formation on M. sativa. We suggest that the production of a series of active signal molecules with different degrees of specificity might be important in controlling the symbiosis of R. meliloti with several different host plants or under different environmental conditions.

Bacterial Adhesion↗
PubMed1991

Six nodulation genes of nod box locus 4 in Rhizobium meliloti are involved in nodulation signal production: nodM codes for D-glucosamine synthetase.

The nucleotide sequence of the nod box locus n4 in Rhizobium meliloti was determined and revealed six genes organized in a single transcriptional unit, which are induced in response to a plant signal such as luteolin. Mutations in these genes influence the early steps of nodule development on Medicago, but have no detectable effect on Melilotus, another host for R. meliloti. Based on sequence homology, the first open reading frame (ORF) corresponds to the nodM gene and the last to the nodN gene of Rhizobium leguminosarum. The others do not exhibit similarity to any genes sequenced so far, so we designated them as nolF, nolG, nolH and nolI, respectively. We found that the n4 locus, and especially the nodM and nodN genes, are involved in the production of the root hair deformation (Had) factor. NodM exhibits homology to amidotransferases, primarily to the D-glucosamine synthetase encoded by the glmS gene of Escherichia coli. We demonstrated that in E. coli the regulatory gene nodD together with luteolin can activate nod genes. On this basis we showed that nodM complemented an E. coli glmS- mutation, indicating that nodM can be considered as a glmS gene under plant signal control. Moreover, exogenously supplied D-glucosamine restored nodulation of Medicago by nodM mutants. Our data suggest that in addition to the housekeeping glmS gene of R. melioti, nodM as a second glmS copy provides glucosamine in sufficient amounts for the synthesis of the Had factor.

Amino Acid Sequence↗