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1.
Hancai Chen James X. Gray Murali Nayudu Michael A. Djordjevic Michael Batley John W. Redmond Barry G. Rolfe 《Molecular & general genetics : MGG》1988,212(2):310-316
Summary R-prime plasmids were constructed from a derivative of Rhizobium strain NGR234 (ANU280) and were shown to contain overlapping genomic DNA segments involved in biosynthesis of exopolysaccharides (EPS). The R-primes originally constructed carried the mutant allele from Tn5-induced EPS-deficient (Exo–) mutant ANU2811. This plasmid-located mutant allele was dominant to the corresponding wild-type allele as merodiploid strains were Exo–. Exo+ revertants occurred at a low rate (1×10-7) and these were shown to result from double reciprocal recombination events, which led to the isolation of R-prime plasmids carrying functional wild-type exo alleles. R-prime plasmids that carry overlapping segments of DNA from parental strain ANU280 complemented 28 of the 30 group 2 Exo– mutants of strain ANU280. Complementation of these Exo– mutants also restored their symbiotic abilities of effective nodulation. Subsequent in vivo recombination between the wild-type alleles located on the R-prime and the corresponding mutated allele on the genome, was used to generate a new family of R-primes, which carried mutations in the exo genes. The 30 group 2 Exo– mutants were classified into 7 distinct genetic groups based upon complementation and physical mapping data. Five of the seven exo loci were gentically linked and located on a 15-kb region of DNA. Mutations at two loci were dominant only when the mutations were R-prime plasmid-located while a mutation at a second locus was cis-dominant to two other exo loci. At least five genes involved in the synthesis of acidic exopolysaccharide synthesis have been identified. 相似文献
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Brant J. Bassam Barry G. Rolfe Michael A. Djordjevic 《Molecular & general genetics : MGG》1986,203(1):49-57
Summary A 6.7 kb HindIII fragment from the Sym-plasmid of strain NGR234 was found to code a nodD-like gene flanked by two loci which were required for siratro host range. Transfer of the 6.7 kb fragment from NGR234 to R. trifolii strain ANU843 conferred extended host range ability to this strain on siratro plants but not to other plants normally nodulated by strain NGR234. Tn5 mutagenesis of the 6.7 kb fragment showed that insertions located into loci flanking the nodD-like gene abolished the extended host range phenotype. A hybridization probe spanning one of the host specificity loci was shown to hybridize to three specific bands in the NGR234 genome. Complementation and DNA hybridization data showed that the nodD-like gene of strain NGR234 was functionally similar to that in R. trifolii. The introduction to R. trifolii of the 6.7 kb HindIII fragment containing Tn5 insertions located in the nodD-like gene did not abolish the ability to extend the host range of R. trifolii to siratro plants. However, transfer of the 6.7 kb HindIII to R. trifolii derivatives containing Tn5 insertions into either nodA, B or C or other R. trifolii nod genes failed to confer siratro nodulation to these recipients. Reconstruction experiments showed that the 6.7 kb fragment from strain NGR234 and the 14 kb nodulation region of R. trifolii could induce the nodulation of siratro plants when introduced together into Sym-plasmid-cured Rhizobium strains. 相似文献
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J P Nap C van de Wiel H P Spaink M Moerman M van den Heuvel M A Djordjevic A A van Lammeren A van Kammen T Bisseling 《Molecular plant-microbe interactions : MPMI》1989,2(2):53-63
The role of the Rhizobium nod genes in the induction of nodulin gene expression was examined by analyzing nodules formed on vetch roots by bacterial strains containing only the nod region. Introduction of an 11-kb cloned nod region of the R. leguminosarum sym plasmid pRL1JI into sym plasmid-cured rhizobia conferred on the recipient strains the ability to induce nodules in which all nodulin genes were expressed. This proves that from the sym plasmid only the nod region is involved in the induction of nodulin gene expression. A transconjugant of Agrobacterium carrying the same nod region induces nodules in which only early nodulin gene expression is detected. Thus, the nod region is essential for the induction of early nodulin gene expression. In this case, nodule cytology may indicate that a defense response of the plant interferes with the induction of late nodulin gene expression. Indirect evidence is presented that indeed the Rhizobium nod genes are also in some way involved in the induction of the expression of late noduling genes. The combination between histological data and pattern of nodulin gene expression furthermore reveals a correlation between nodule structure and nodulin gene expression. This correlation may aid in speculations about the functions of nodulins. 相似文献
7.
Djordje Boskov Mirjana Jocic Ksenija Jovanovic Milos Ljubisavljevic Radmila Anastasijevic 《Biological cybernetics》1994,71(4):341-348
Spike discharges of skeletomotor neurons innervating triceps surae muscles elicited by white noise modulated transmembrane
current stimulation and muscle stretch were studied in decerebrated cats. The white noise modulated current intensity ranged
from 4.3 to 63.2 nA peak-to-peak, while muscle stretches ranged from 100 μm to 4.26 mm peak-to-peak. The neuronal responses
were studied by averaging the muscle length records centered at the skeletomotor action potentials (peri-spike average, PSA)
and by Wiener analysis. Skeletomotor spikes appeared after a sharp peak in PSA of the injected current, preceded by a longer-lasting
smaller wavelet of either depolarizing or hyperpolarizing direction. The PSA amplitude was not related to the injected current
amplitude nor showed any differences related to the motor unit type. The PSA amplitudes were virtually independent of the
stretching amplitude σ, after an initial increase with stretching amplitudes in the range of 15–40 μm (S.D.), or 100–270 μm
peak-to-peak.Analyses of cross-spectra indicated a small or absent increase in gain with frequency in response to injected
current, but about 20 dB/decade in the range 10–100 Hz in response to muscle stretch. The peaks of both Wiener kernels in
response to current injection appear to decrease with the amplitude of injected current, but this decrease was not statistically
significant. The narrow first-order kernels suggest that the transfer function between the current input and spike discharge
is lowpass with a wide passband, i.e. there is very little change in dynamics. The values of the second-order kernels appear
to be nonzero only along the main diagonal. This is characteristic of a simple Hammerstein type cascade, i.e. a zero memory
nonlinearity followed by a linear system. Small values of second-order kernels away from the origin and narrow first-order
kernels suggest that the linear cascade contributes very little to the overall dynamic response.In contrast to Wiener kernels
found in response to current injection, the Wiener kernels in response to stretch showed a decreasing trend with stretch amplitude.
The size of the second-order kernels decreased to a somewhat larger extent with input amplitude than that of the first-order
kernels, indicating an amplitude-dependent nonlinearity. Overall, the transformation between length and spike output was described
as an LNNL cascade with second-order nonlinearities.
Received: 1 April 1993/Accepted in revised form: 24 March 1994 相似文献
8.
Summary A microscopic assessment is presented of the comparative infection capacity of wild-type and hybrid strains ofRhizobium leguminosarum bv.viciae withR. l. bv.trifolii strain ANU 843 on white clover seedlings. TheR. l. bv.viciae hybrid strains contained defined DNA segments coding for different combinations ofR. l. bv.trifolii host-specific nodulation genes. White clover plants were examined over a 72 h period to assessRhizobium infectivity, the morphological changes in root hair growth; colonisation ability of rhizobia; infection thread initiation and the ability to induce cortical cell division.R. l. bv.viciae strain 300 induced root hair curling more slowly than strain ANU 843 or any of the hybrid strain 300 bacteria, and when curling had taken place, there was poorer colonization by strain 300 within the folded hair cell, no evidence of infection thread formation and only limited cortical cell division 72 h after inoculation. The addition of the host-specific nodulation genes ofR. l. bv.trifolii to strain 300 was necessary to induce infection threads and establish a normal pattern of nodulation of the roots of white clovers. 相似文献
9.
Rakić Tamara Pešić Mila Kostić Nikola Andrejić Gordana Fira Djordje Dželetović Željko Stanković Slaviša Lozo Jelena 《Plant and Soil》2021,462(1-2):349-363
Plant and Soil - Flotation tailings represent an extremely unfriendly substrate for plant colonization due to toxic metal concentrations and marked macronutrient deficiencies. The perennial grass... 相似文献
10.
Ulrich Grädler Daniel Schwarz Verena Dresing Djordje Musil Jörg Bomke Matthias Frech Hartmut Greiner Stefan Jäkel Thomas Rysiok Dirk Müller-Pompalla Ansgar Wegener 《Journal of molecular biology》2013,425(2):309-333
Syk is an essential non-receptor tyrosine kinase in intracellular immunological signaling, and the control of Syk kinase function is considered as a valuable target for pharmacological intervention in autoimmune or inflammation diseases. Upon immune receptor stimulation, the kinase activity of Syk is regulated by binding of phosphorylated immune receptor tyrosine-based activating motifs (pITAMs) to the N-terminal tandem Src homology 2 (tSH2) domain and by autophosphorylation with consequences for the molecular structure of the Syk protein. Here, we present the first crystal structures of full-length Syk (fl-Syk) as wild type and as Y348F,Y352F mutant forms in complex with AMP-PNP revealing an autoinhibited conformation. The comparison with the crystal structure of the truncated Syk kinase domain in complex with AMP-PNP taken together with ligand binding studies by surface plasmon resonance (SPR) suggests conformational differences in the ATP sites of autoinhibited and activated Syk forms. This hypothesis was corroborated by studying the thermodynamic and kinetic interaction of three published Syk inhibitors with isothermal titration calorimetry and SPR, respectively. We further demonstrate the modulation of inhibitor binding affinities in the presence of pITAM and discuss the observed differences of thermodynamic and kinetic signatures. The functional relevance of pITAM binding to fl-Syk was confirmed by a strong stimulation of in vitro autophosphorylation. A structural feedback mechanism on the kinase domain upon pITAM binding to the tSH2 domain is discussed in analogy of the related family kinase ZAP-70 (Zeta-chain-associated protein kinase 70). Surprisingly, we observed distinct conformations of the tSH2 domain and the activation switch including Tyr348 and Tyr352 in the interdomain linker of Syk in comparison to ZAP-70. 相似文献