Mutant PCNA alleles are associated with cdc phenotypes and sensitivity to DNA damage in fission yeast

Twenty-eight site-directed mutations were introduced into the fission yeast gene (pcn1 ⁺) that encodes proliferating cell nuclear antigen (PCNA) and their in vivo effects analyzed in a strain with a null pcn1 background. Mutants defective in enhancing processivity of DNA polymerase δ have previously been identified. In this study, we assessed all of the mutants for their sensitivities to temperature, hydroxyurea, UV irradiation and methyl methanesulfonate (MMS), and specific mutants were also tested for sensitivity to γ irradiation. One cold-sensitive allele, pcn1-3, was characterized in detail. This mutant had a recessive cold-sensitive cdc phenotype and showed sensitivity to hydroxyurea, UV, and γ irradiation. At the non-permissive temperature pcn1-3 protein was able to form homotrimers in solution and showed increased stimulation of both synthetic activity and processivity of DNA polymerase δ relative to the wild-type Pcn1⁺ protein. Epistasis analyses indicated that pcn1-3 is defective in the repair pathway involving rad2 ⁺ but not defective in the classical nucleotide excision repair pathway involving rad13 ⁺ . Furthermore, pcn1-3 is either synthetically or conditionally lethal in null checkpoint rad backgrounds and displays a mitotic catastrophe phenotype in these backgrounds. A model for how pcn1-3 defects may affect DNA repair and replication is presented. Received: 5 July 1997 / Accepted: 10 October 1997     

Australian Anthropology,Ideology and Political Repression: The Cold War Experience of Frederick G. G. Rose

It is more than half a century since Frederick G. G. Rose (1915–1991) published his classic text, The classification of kin, age structure and marriage amongst the Groote Eylandt Aborigines: A study in method and a theory of kinship (1960) in the former German Democratic Republic. Although the fieldwork for his thesis had been carried out in Australia on Groote Eylandt in 1938 and 1941, a conservative academic establishment and the political climate of the Cold War postponed its publication until 1960. Why were Rose's fieldwork findings suppressed by the powerful gate-keeper of Australian anthropology, Professor Adolphus Peter Elkin (1891–1979)? Moreover, why was Rose later denied a government permit to revisit Groote Eylandt and Central Australia to further his research? This paper examines the early work of the communist anthropologist, Frederick Rose, within the broad context of Western post-war anthropological developments, an expanding capitalist economy and the political tensions of the Cold War era. As a communist and public servant from 1938 to 1954, Rose was forced, after the Petrov Royal Commission cast him under a cloud of suspicion, to seek institutional support for his academic career in the German Democratic Republic.     

Protein diffusion in crowded electrolyte solutions

We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models.     

Land surface phenology as an indicator of biodiversity patterns

With the rapid decline in biodiversity worldwide it is imperative to develop procedures for assessing changes in biodiversity across space. The synoptic view provided by imaging remote sensors constitutes a suitable approach for analyzing biodiversity from local to regional scales. A procedure based on the close relationship between floristic similarity and the similarity in land surface phenology was recently developed and successfully applied to assess diversity patterns using time series imagery acquired by the Moderate Resolution Imaging Spectro-radiometer (MODIS). However, as it depends on high temporal resolution remotely sensed data (e.g., MODIS), the procedure is constrained by the coarse spatial resolution characterizing these high temporal resolution data. Using an optimized technique for image fusion, we combined high temporal resolution data acquired by the MODIS sensor system with moderate spatial resolution data acquired by the Landsat TM/ETM+ sensor systems. Our results show that the MODIS/Landsat data fusion allows the characterization of land surface phenology at higher spatial resolutions, which better corresponded with information acquired within vegetation survey plots established in temperate montane forests located in Wolong Nature Reserve, Sichuan Province, China. As such, the procedure is useful for capturing changes in biodiversity induced by disturbances operating at large spatial scales and constitutes a suitable tool for monitoring and managing biodiversity.     

Ecology,distribution mapping and conservation implications of four critically endangered endemic plants of Kashmir Himalaya

During the last few decades, human-driven activities have led to indiscriminate habitat destruction and exploitation of many plant species in Kashmir Himalaya. As a result, many species have become threatened and are struggling for survival. Of particular concern are the endemic and critically endangered species which have the highest risk of the extinction, hence warranting immediate conservation actions. Therefore the current study was carried out to understand the distribution, ecology and conservation implications of the four critically endangered endemic plants of Kashmir Himalaya. Habitat distribution modelling showed that the suitable potential areas for the species occurred from subalpine to alpine meadowlands with an elevational range of 1500–4600 m asl. The output of the MaxEnt model and field surveys have revealed that their highest potential distribution is in Panchari, Khrew, Ramnagar, Pahalgam, Gurez, Sonamarg, Gulmarg and Kishtwar forest ranges. Based on the field explorations and herbarium records, Saussurea costus (Falc.) Lipsch have 27 distribution areas, Gentiana kurroo Royle 18, Lilium polyphyllum D. Don 12 and Aconitum chasmanthum Stapf have 15. Precipitation of the driest month and annual mean temperature played an important role in the distribution of the studied species. The species started their lifecycle with the onset of the spring season, flowered in summer, fruit in autumn and senesce in the winter season. Under natural conditions, the number of days required for germination ranged from 180 to 210 where cold stratification played a pivotal role. Since last few decades, the populations of these species have been shrinking in their natural habitats due to over-exploitation for medicinal purposes and habitat destruction through amplified humanoid interferences like the expansion of agricultural land, road building, grazing and urbanization. Thus there is an urgent need to come up with positive strategies to save whatever is left and plan long term rescue measures not only to protect these species from extinction but also to reintroduce them along with framing the plans to supply sustained raw materials for medicine.     

The effect of caffeine,different fixation regimes and low temperature on microtubules in the cells of higher plants

Caffeine, (1:3:7-tri-methyl-xanthine), either as a prefixation treatment or included with glutaralde-hyde as the primary fixative, destroys or disorganises the microtubules associated with the formation of secondary walls in fibres from the flowering stem of the grass Lolium temulentum L. There is no observable effect of caffeine treatment on the microtubules associated with primary wall formation in collenchyma and young fibres from L. temulentum or in root cap cells of Zea mays L. and Phaseolus vulgaris L. The microtubules associated with primary wall formation are destroyed by cold treatment but not those associated with secondary wall formation. Tannic acid included in the fixative shows the microtubules associated with secondary wall formation in fibres of L. temulentum to be composed of 13 subunits. Treatment with lanthanum hydroxide does not stain the core or the halo of the microtubules.Abbreviation PIPES Piperazine N-N- bis 2 ethanol sulphonic acid The Grassland Research Institute is financed through the Agricultural Research Council     

Psychrotolerant bacteria isolated from the leaf apoplast of cold-adapted wild plants improve the cold resistance of bean (Phaseolus vulgaris L.) under low temperature

We have isolated psychrotolerant bacteria from the leaf apoplast of cold-adapted wild plants and aimed to investigate their effect on the cold resistance of bean (Phaseolus vulgaris L.). Based on the findings of 16S rRNA gene sequence analysis, 20 isolates belonging to 5 bacteria species (Pseudomonas fragi, P. chloropaphis, P. fluorescens, P. proteolytica and Brevibacterium frigoritolerans) were identified in the leaf apoplastic fluid of Draba nemorosa, Galanthus gracilis, Colchicum speciousum, Scilla siberica, Erodium cicutarium, respectively. We have determined that 6 of the 20 isolates have exhibited ACC (1-aminocyclopropane-1-carboxylate) deaminase activity and secreted different extracellular proteins under cold condition (+4 °C) compared to normal growth condition (28 °C). The six isolates were then inoculated independently of each other to the leaves of 10-day-old bean seedlings growing under normal conditions (25/22 °C, 16/8 h photoperiod), and the inoculated and uninoculated (control) seedlings were transferred to cold (9/5 °C, 16/8 h photoperiod) for 3 days. The bacterial inoculations have decreased freezing injury, ice nucleating activity and lipid peroxidation content in parallel with the decrease of reactive oxygen species level such as O₂^.- and H₂O₂ in the inoculated seedlings compared to the control. In addition, the inoculations of the isolates have stimulated the activity of apoplastic antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione reductase. The results show that the inoculations improve the cold resistance of bean seedlings and the psychrotolerant bacterial isolates can be evaluated within the group of plant growth promoting bacteria (PGPB) which can increase tolerance of cold-sensitive crops.     

Isolation and characterization of Zymomonas mobilis mutants resistant to octadecyltrimethylammonium chloride,a detergent acting on hopanoid-producing bacteria

Growth of the hopanoid-producing bacterium Zymomonas mobilis was inhibited at low concentrations of the cationic detergent octadecyltrimethylammoniumchloride (OTAC). A relationship between sensitivity of Zymomonas mobilis to OTAC, presence of hopanoids and ethanol tolerance was postulated. Mutants resistant to OTAC were isolated from strains ZM1 and ZM4. They did not present any alteration of the hopanoid content and their squalene cyclases showed the same sensitity to OTAC as the parent enzymes. Resistance to OTAC paralleled pleiotropic effects including, enhanced accessibility of the membrane-bound alkaline phosphatase, important release of proteins from cells by Tris/HCl treatment, increased resistance to antibiotics and increased sensitivity to ethanol. In addition, OTAC^R mutants were also characterized by the synthesis or the overproduction of an outer membrane protein (F53) not detected on 2D-PAGE maps of parent strains and by a normal heat shock response. The role of hopanoids, heat shock proteins, protein F53 and membrane organization in ethanol tolerance is discussed.Abbreviations OTAC octadecyltrimethylammoniumchloride - SLS sodium lauryl sarcosinate