Mating system in a population of the wasp <Emphasis Type="Italic">Polistes dominulus</Emphasis> (Christ) (Hymenoptera,Vespidae)

The specific features of mating females and males of different morphs collected from a population of the wasp P. dominulus in Southern Ukraine were studied. Data analysis of mating individuals in experiments indicated a random mate choice by size and assortative mating by coloration. The most actively copulating males in the experiments had light-colored mesopleuron, sternite, and fore and middle coxae. They were similar in the color pattern and size to resident males, which defend their territories in the habitat. Most P. dominulus females mated only once. In their coloration, those females represented the majority of the individuals in the population. The color variability of the foundresses was shown to change in a cyclic pattern. The possibility that such variability may result from selective or assortative mating is discussed. The color and pattern traits of P. dominulus females and males could serve as markers of their reproductive strategies and their reproductive success on the whole.     

Reproductive strategies of male paper wasps (Hymenoptera,Vespidae) in the southern Dnieper area

The reproductive strategies of Polistes nimphus (Chris) and P. gallicus (L.) males in the Low Dnieper area are described. In the P. nimphus population, territorial and migrating males were observed. The territorial males of P. gallicus formed swarms or patrolled their areas singly. The male color variants and size were shown to correlate with their reproductive strategies. The territorial males of P. nimphus had a paler coloration and smaller head and wings than migrating males. The swarming territorial males of P. gallicus were paler and had a larger head and wings than single territorial males. The geographic variability of precopulatory behavior of males of the studied species is discussed.     

GABA in brain tissue of paroxysmal (px) chick

An investigation was made of GABA in whole brain and brain regions of paroxysmal (px) chicks. Whole brain levels of GABA were higher (P less than 0.05) in px chicks than in normal siblings by day 10 post-hatching. GABA in brain areas containing degeneration of auditory and vestibular nuclei and tracts was also found to be higher (P less than 0.05) in px chicks. These data indicate that a dysfunction of the GABA pathway occurs early in the px syndrome, possibly as a causative factor.     

Electron microscopic studies of sequence-specific recognition of duplex DNA by different ligands

The following ligands were used to study sequence specific recognition of duplex DNA by electron microscopic techniques: methyltransferases BspR1 and EcoR124 (recognition sequences GGCC and GAAN7RTCG, respectively), a biotinylated deoxyoligonucleotide 5′-CTCTCTCTCTCTCT-3′ capable of forming triplex DNA, and PNA oligomer H-T₁₀-LysNH₂. For each ligand the best conditions for electron microscopic (EM)detection of stable specific complex formation were determined. It was demonstrated that EM allowed us to determine the position of the individual target site with an error of 15–20 bp, the relative affinities for individual target sites and kinetic parameters of the binding. These results open new possibilities for EM investigations of sequence-specific interactions with a wide range of other ligands of a similar nature. They also imply that a wide range of different sequences can be unambiguously and precisely mapped by EM and greatly extend the scope of EM applications for physical mapping of genomic DNA.     

High-level expression of the cloned genes encoding the subunits of and intact DNA methyltransferase, M.EcoR124.

We have cloned the genes coding for the two subunits (HsdM and HsdS) of the type-I DNA methyltransferase (MTase), M.EcoR124, into the specially constructed expression vector, pJ119. These subunits have been synthesized together as an intact MTase. We have also cloned the individual subunit-encoding genes under the control of the T7 gene 10 promoter or the lacUV5 promoter. High levels of expression have been obtained in all cases. While HsdM was found to be soluble, HsdS was insoluble. However, in the presence of the co-produced HsdM subunit, HsdS was found in the soluble fraction as part of an active MTase. We have partially purified the cloned multi-subunit enzyme and shown that it is capable of DNA methylation both in vivo and in vitro.     

Protein-polymer nano-machines. Towards synthetic control of biological processes

The exploitation of nature's machinery at length scales below the dimensions of a cell is an exciting challenge for biologists, chemists and physicists, while advances in our understanding of these biological motifs are now providing an opportunity to develop real single molecule devices for technological applications. Single molecule studies are already well advanced and biological molecular motors are being used to guide the design of nano-scale machines. However, controlling the specific functions of these devices in biological systems under changing conditions is difficult. In this review we describe the principles underlying the development of a molecular motor with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for control of the motor function. The molecular motor is a derivative of a TypeI Restriction-Modification (R-M) enzyme and the synthetic polymer is drawn from the class of materials that exhibit a temperature-dependent phase transition.The potential exploitation of single molecules as functional devices has been heralded as the dawn of new era in biotechnology and medicine. It is not surprising, therefore, that the efforts of numerous multidisciplinary teams 12. have been focused in attempts to develop these systems. as machines capable of functioning at the low sub-micron and nanometre length-scales 3. However, one of the obstacles for the practical application of single molecule devices is the lack of functional control methods in biological media, under changing conditions. In this review we describe the conceptual basis for a molecular motor (a derivative of a TypeI Restriction-Modification enzyme) with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for controlling the motor function 4.     

No Evidence of Conpopulation Sperm Precedence between Allopatric Populations of House Mice

Investigations into the evolution of reproductive barriers have traditionally focused on closely related species, and the prevalence of conspecific sperm precedence. The effectiveness of conspecific sperm precedence at limiting gene exchange between species suggests that gametic isolation is an important component of reproductive isolation. However, there is a paucity of tests for evidence of sperm precedence during the earlier stages of divergence, for example among isolated populations. Here, we sourced individuals from two allopatric populations of house mice (Mus domesticus) and performed competitive in vitro fertilisation assays to test for conpopulation sperm precedence specifically at the gametic level. We found that ova population origin did not influence the outcome of the sperm competitions, and thus provide no evidence of conpopulation or heteropopulation sperm precedence. Instead, we found that males from a population that had evolved under a high level of postcopulatory sexual selection consistently outcompeted males from a population that had evolved under a relatively lower level of postcopulatory sexual selection. We standardised the number of motile sperm of each competitor across the replicate assays. Our data therefore show that competitive fertilizing success was directly attributable to differences in sperm fertilizing competence.     

Genetic and physical studies of restriction-deficient mutants of the Inc FIV plasmids R124 and R124/3

Summary R124 and R124/3 are R plasmids that carry the genes for two different restriction and modification systems. The phenotype of strains carrying either of these plasmids along with the F'lac ⁺ plasmid, is restriction-deficient (Res^-). The Res^- phenotype is not due to selection of preexisting mutants but rather to a complex mutational event caused by the F plasmid. Restriction-deficient mutants carry extensive deletions and other DNA rearrangements. Tn7 insertion is used to locate the restriction gene. Many of the Res^- mutants are genetically unstable and revert at exceptionally high frequencies. Reversion is accompanied by DNA rearrangements which result in a net gain of 9 kb of DNA. F derivates of F⁺ which do not cause restriction-deficiency but do cause deletion were used to distinguish between the DNA rearrangements associated with restriction-deficiency and those associated with deletion. From Res⁺ revertants of strains carrying F'lac ⁺ and R124 or R124/3 we have isolated F plasmids that now carry the genes for the R124 or R124/3 restriction and modification systems. It is suggested that interaction between part of the F plasmid and that segment of the R plasmid which controls the switch in Res-Mod specificity which has been observed (Glover et al. 1983) is responsible for the production of restriction-deficiency.     

Cloning, production and characterisation of wild type and mutant forms of the R.EcoK endonucleases.

The hsdR, hsdM and hsdS genes coding for R.EcoK restriction endonuclease, both with and without a temperature sensitive mutation (ts-1) in the hsdS gene, were cloned in pBR322 plasmid and introduced into E.coli C3-6. The presence of the hsdSts-1 mutation has no effect on the R-M phenotype of this construct in bacteria grown at 42 degrees C. However, DNA sequencing indicates that the mutation is still present on the pBR322-hsdts-1 operon. The putative temperature-sensitive endonuclease was purified from bacteria carrying this plasmid and the ability to cleave and methylate plasmid DNA was investigated. The mutant endonuclease was found to show temperature-sensitivity for restriction. Modification was dramatically reduced at both the permissive and non-permissive temperatures. The wild type enzyme was found to cleave circular DNA in a manner which strongly suggests that only one endonuclease molecule is required per cleavage event. Circular and linear DNA appear to be cleaved using different mechanisms, and cleavage of linear DNA may require a second endonuclease molecule. The subunit composition of the purified endonucleases was investigated and compared to the level of subunit production in minicells. There is no evidence that HsdR is prevented from assembling with HsdM and HsdSts-1 to produce the mutant endonuclease. The data also suggests that the level of HsdR subunit may be limiting within the cell. We suggest that an excess of HsdM and HsdS may produce the methylase in vivo and that assembly of the endonuclease may be dependent upon the prior production of this methylase.