Genetic mapping of tyramine oxidase and arylsulfatase genes and their regulation in intergeneric hybrids of enteric bacteria.

The genes for arylsulfatase (atsA) and tyramine oxidase (tynA) have been mapped in Klebsiella aerogenes by P1 transduction. They are linked to gdhD and trp in the order atsA-tynA-gdhD-trp-pyrF. Complementation analysis using F' episomes from Escherichia coli suggested an analogous location of these genes in E. coli, although arylsulfatase activity was not detected in E. coli. P1 phage and F' episomes were used to create intergeneric hybrid strains of enteric bacteria by transfer of the ats and tyn genes between K. aerogenes, E. coli, and Salmonella typhimurium. Intergeneric transduction of the tynK gene from K. aerogenes to an E. coli restrictionless strain was one to two orders less frequent than that of the leuK gene. The tyramine oxidase of E. coli and S. typhimurium in regulatory activity resemble very closely the enzyme of K. aerogenes. The atsE gene from E. coli was expressed, and latent arylsulfatase protein was formed in K. aerogenes and S typhimurium. The results of tyramine oxidase and arylsulfatase synthesis in intergeneric hybrids of enteric bacteria suggest that the system for regulation of enzyme synthesis is conserved more than the structure or function of enzyme protein during evolution.     

Tryptophan operon regulation in interspecific hybrids of enteric bacteria.

We examined tryptophan regulation in merodiploid hybrids in which a plasmid carrying the trp operon of Escherichia was introduced into Trp mutants of other enteric genera, or in which a plasmid carrying the trpR+ (repressor) gene of E. coli was transfered into fully constitutive trpR mutants of other genera. In these hybrids the trp operon of one species is controlled by the repressor of a different species. Similar investigations were possible in transduction hybrids in which either the trp operon or the trpR+ locus of Shigella dysenteriae was introduced into E. coli. Our measurements of trp enzymes levels in repressed and nonrepressed cells indicate that Trp regulation is normal, with only minor quantitative variations, in hybrids between E coli and Shigella dysenteriae, Salmonella typhimurium, Klebsiella aerogenes, Serratia marcescens, and Proteus mirabilis. Our results support the idea that a repressor-operator mechanism for regulating trp messenger ribonucleic acid production evolved in a common ancestor of the enteric bacteria, and that this repressor-operator recognition has been conversed during the evolutionary divergence of the Enterobacteriaceae.     

Monopolar spindles in meiosis of intergeneric cereal hybrids

Monopolar spindles in pollen mother cells of cereal wide F1 hybrids are described; details of the formation of anastral spindles are discussed.     

Regulation of nuclear DNA synthesis in amoeba interspecific hybrids

Interspecific hybrids between A. proteus and A. indica which have different durations of nuclear S periods have been produced by reciprocal nuclear transfer after enucleating the host cells. The duration of nuclear DNA synthesis was studied in the clones of these interspecific hybrids and parental stocks by ³H-thymidine autoradiography. These studies showed that nuclear S period of the hybrids changed to that characteristic to the nuclear component of the parental cell from which the hybrid's original cytoplasm was derived. The results of these studies were interpreted as evidence for cytoplasmic regulation of the rate of chromosome replication.     

Karyotype stabilization in intergeneric hybrids of the subtribe Triticinae

Summary The C-banded data obtained from Triticinae hybrids are studied with reference to the stabilization of their karyotypes. The types of hybrids distinguished according to genome structure are type I with minimally one diploid genome and type II with a haploid set only. Comparative analysis demonstrates that type I differs from II in karyotype stabilization. The chromosomes from various haploid genomes are combined into new genomes in type I; type II is represented only by amphiploids with the complete set of the chromosomes from all the genomes. The meiotic behaviour of the haploid genome chromosomes were found to have a modifying effect on karyotype stabilization: type II becomes I when homoeologous pairing level is high and when it is associated with the reductional division of univalents.The paper is dedicated to the memory of Professor V. V. Khvostova     

Regulation of chlorophyll synthesis in photosynthetic bacteria

Energy-transducing membranes of the nonsulfur purple photosynthetic bacteria are known to contain several species of bacteriochlorophyll (BChl) complexes. The reaction-centre complex (rc-BChl) is the locus of the charge separation that provides the poles of the photochemical electron transport system, whereas the other complexes serve lightharvesting functions. This report summarizes an investigation of the general features of the control mechanisms governing synthesis of the several chlorophyll complexes inRhodopseudomonas capsulata. The results obtained indicate a close biosynthetic association between rc-BChl and one of the light-harvesting chlorophylls (complex I). Regulation of synthesis of light-harvesting complex II (during anaerobic photosynthetic growth) appears to be relatively independent, and intimately related to the energy state of the cell. Chlorophyll synthesis inR. capsulata cells growing aerobically in darkness was also studied. The presence of functional photosynthetic units in dark-grown cells, of very low BChl content, was clearly evidenced by demonstration of: the potentiality for resumption of anaerobic photosynthetic growth, light-induced oxidation of cytochrome₅₅₂ in vivo, and high photophosphorylation capacity (relative to BChl) of membrane fragments from such cells. Synthesis of light-harvesting BChl complex II is particularly inhibited in cells growing in darkness with respiratory phosphorylation as the source of energy, and it is suggested that this complex is a primary target of the biosynthetic control devices activated by change of light intensity or presence of molecular oxygen during growth of nonsulfur purple bacteria.     

Genetic processes in intergeneric cell hybrids Atropa + Nicotiana

Summary The genetic constitution of the cell hybrids Atropa belladonna + Nicotiana chinensis, obtained by cloning of individual heteroplasmic protoplast fusion products (Gleba et al. 1982) and cultured in vitro for 12 months, has been studied. The study comprised 11 hybrid cell clones of independent origin and included analysis of a) chromosome number, size, morphology, and relative position in metaphase plates, b) multiple molecular forms of the enzymes esterase and amylase, and c) relative nuclear DNA content. The data obtained permit us to conclude that, after one year of unorganized growth in vitro, the cells of most (8) clones had retained chromosomes of both parents, while species-specific elimination of nearly all Atropa chromosomes had occurred in three clones. About half of the non-segregating clones possess 120–150 chromosomes including 50–70 of Atropa and 50–90 of Nicotiana. Other clones are polyploid and possess 200–250 chromosomes with a predominance of either Atropa or Nicotiana chromosome types. Only a few chromosomal changes (reconstituted chromosomes, ring chromosomes) have been detected. In some metaphase plates, chromosomes of the two parents tend to group separately, indicating non-random arrangement of chromosomes of the two parents within the hybrid nucleus. Cytophotometric studies of the relative nuclear DNA content showed that distribution histograms for cell clones were similar to those of non-hybrid cultured cells. Cell populations were relatively homogenous and do not indicate any genetic instability as a result of hybridization between remote plant species. Biochemical analysis of isoenzyme patterns confirmed that in most cell clones, species-specific multiple molecular forms of esterase and amylase from both parents were present, i.e. genetic material of both parental species was expressed in the cell hybrids.Dedicated to Professor G. Melchers with gratitude     

Rapid genomic changes in interspecific and intergeneric hybrids and allopolyploids of Triticeae.

Allopolyploidy is preponderant in plants, which often leads to speciation. Some recent studies indicate that the process of wide hybridization and (or) genome doubling may induce rapid and extensive genetic and epigenetic changes in some plant species and genomic stasis in others. To further study this phenomenon, we analyzed three sets of synthetic allopolyploids in the Triticeae by restriction fragment length polymorphism (RFLP) using a set of expressed sequence tags (ESTs) and retrotransposons as probes. It was found that 40-64.7% of the ESTs detected genomic changes in the three sets of allopolyploids. Changes included disappearance of parental hybridization fragment(s), simultaneous appearance of novel fragment(s) and loss of parental fragment(s), and appearance of novel fragment(s). Some of the changes occurred as early as in the F1 hybrid, whereas others occurred only after allopolyploid formation. Probing with retrotransposons revealed numerous examples of disappearance of sequences. No gross chromosome structural changes or physical elimination of sequences were found. It is suggested that DNA methylation and localized recombination at the DNA level were probably the main causes for the genomic changes. Possible implications of the genomic changes for allopolyploid genome evolution are discussed.     

Inducible xylitol dehydrogenases in enteric bacteria.

Morganella morganii ATCC 25829, Providencia stuartii ATCC 25827, Serratia marcescens ATCC 13880, and Erwinia sp. strain 4D2P were found to induce a xylitol dehydrogenase when grown on a xylitol-containing medium. The xylitol dehydrogenases were partially purified from the four strains, and those from M. morganii ATCC 25829, P. stuartii ATCC 25827, and S. marcescens ATCC 13880 were all found to oxidize xylitol to D-xylulose. These three enzymes had KmS for xylitol of 7.1 to 16.4 mM and molecular weights ranging from 130,000 to 155,000. In contrast, the xylitol dehydrogenase from Erwinia sp. strain 4D2P oxidized xylitol at the C-4 position to produce L-xylulose, had a Km for xylitol of 72 mM, and had a molecular weight of 102,000.     

Evolution of chemotactic-signal transducers in enteric bacteria.

The methyl-accepting chemotactic-signal transducers of the enteric bacteria are transmembrane proteins that consist of a periplasmic receptor domain and a cytoplasmic signaling domain. To study their evolution, transducer genes from Enterobacter aerogenes and Klebsiella pneumoniae were compared with transducer genes from Escherichia coli and Salmonella typhimurium. There are at least two functional transducer genes in the nonmotile species K. pneumoniae, one of which complements the defect in serine taxis of an E. coli tsr mutant. The tse (taxis to serine) gene of E. aerogenes also complements an E. coli tsr mutant; the tas (taxis to aspartate) gene of E. aerogenes complements the defect in aspartate taxis, but not the defect in maltose taxis, of an E. coli tar mutant. The sequence was determined for 5 kilobases of E. aerogenes DNA containing a 3' fragment of the cheA gene, cheW, tse, tas, and a 5' fragment of the cheR gene. The tse and tas genes are in one operon, unlike tsr and tar. The cytoplasmic domains of Tse and Tas are very similar to those of E. coli and S. typhimurium transducers. The periplasmic domain of Tse is homologous to that of Tsr, but Tas and Tar are much less similar in this region. However, several short sequences are conserved in the periplasmic domains of Tsr, Tar, Tse, and Tas but not of Tap and Trg, transducers that do not bind amino acids. These conserved regions include residues implicated in amino-acid binding.