Nuclear distribution and chromatin association of DNA polymerase α-primase is affected by TEV protease cleavage of Cdc23 (Mcm10) in fission yeast

Background  

Cdc23/Mcm10 is required for the initiation and elongation steps of DNA replication but its biochemical function is unclear. Here, we probe its function using a novel approach in fission yeast, involving Cdc23 cleavage by the TEV protease.     

Effect of microgravity on plasma catecholamine responses to stressors during space flight

The effect of microgravity on the sympathicoadrenal system (SAS) activity in humans and animals has not yet been clarified. Our previous studies suggested that the SAS activity, evaluated by circulating and/or urinary catecholamine (CA) levels in astronauts during space flights, was found to be rather unchanged. However, CA levels were measured in astronauts only at rest conditions. The aim of the present study was to investigate effect of microgravity during space flight and post-flight readaptation on responsiveness of the SAS to somatic and psychic stressors evaluated by levels of catecholamines and their metabolite in the blood of the Slovak cosmonaut during his stay on board the space station Mir.     

Modification of pectin with UV-absorbing substitutents and its effect on the structural and hydrodynamic properties of the water-soluble derivatives

Citrus pectin with a low degree of methyl esterification (LMP) and its deesterified form, potassium pectate (KP), were modified with a low amount of UV-absorbing substituents. For this purpose, two different substitution reactions were used (a) alkylation of hydroxyl groups with p-carboxybenzyl bromide in aqueous alkali and (b) alkylation of the carboxylate group with benzyl bromide in the DMSO/TBAI/catalyst system. Chemical and spectroscopic methods reveal a low degree of substitution (DS<0.1) for the derivatives. The hydrodynamic properties were assessed by analytical ultracentrifugion, viscometry, and HPGPC. The results indicate that the introduction of small amounts of p-carboxybenzyl ether groups practically had no effect on the hydrodynamic properties in the case of KP, whereas, it was accompanied with a decrease of the molecular mass for LMP. The degradation was more pronounced during the benzyl esterification of LMP. The results confirmed that LMP is susceptible to chain cleavage due to β-elimination during both modification reactions. However, KP seems to be more tolerant of the reaction conditions.     

Insect feeding deterrent activity of bisabolangelone and of some sesquiterpenes of eremophilane type

The insect feeding deterrent activity of some sesquiterpenes of furanoeremophilane type and of the related eremophilanolide type were tested towards three selected storage pests: Sitophilus granarius, Tribolium confusum and Trogoderma granarium. The results were compared with the biogenetically related compound of bakkenolide type, known as a potent antifeedant. Bisabolangelone, tested on the same insects, exhibited the strongest activity, and may be included in the class of very good insect feeding deterrents. The antifeeding activity of bisabolangelone and bakkenolide A towards larvae of Leptinotarsa decemlineata was also observed.     

The Langhian (Middle Badenian) carbonate production event in the Moravian part of the Carpathian Foredeep (Central Paratethys): a multiproxy record

The carbonate production event in the Moravian part of the Carpathian Foredeep is known as a deposition of a carbonate–siliciclastic complex in the marginal part of the basin, correlating with the time period from the last occurrence of Helicosphaera waltrans (14.36 Ma) to the last occurrence of Sphenolithus heteromorphus (13.34 Ma). Sedimentological and microfacial data, analysis of foraminifera, calcareous nannoplankton, red algae, mollusks, palynology, as well as oxygen and carbon stable isotopes from foraminiferal tests, were used to interpret the specific paleoenvironment of the carbonate production event. The event was accelerated by a decrease of terrigenous input due to a large transgression and, primarily, an increasingly arid climate. Production of carbonate was related to oligotrophic conditions, expansion of sea-grass meadows, summer downwelling circulations and winter stratification of the water column. Autochthonous and semi-autochthonous carbonates were deposited in shallow-water near the fair-weather wave-base; allochthonous carbonates were transported to the outer shelf by gravity flows. Climatic instability and relative sea-level changes, induced mainly by substantial tectonic activity, caused the carbonate bodies to be small with a high ratio of siliciclastic components, indicating only a short-term and spatially restricted environment suitable for carbonate production. Exceptionally, carbonate production persisted longer during the whole sea-level cycle (“Rousínov Ridge”). Siliciclastic intercalations in these larger limestone bodies represent catastrophic rain events that transported a higher amount of terrigenous material into the basin. The specific climatic conditions of the carbonate production event, namely climatic instability and aridification with episodic intensive rain, were associated with the Middle Miocene climatic transition in the study area.     

Ultrastructural Changes Caused by Snf7 RNAi in Larval Enterocytes of Western Corn Rootworm (Diabrotica virgifera virgifera Le Conte)

The high sensitivity to oral RNA interference (RNAi) of western corn rootworm (WCR, Diabrotica virgifera virgifera Le Conte) provides a novel tool for pest control. Previous studies have shown that RNAi of DvSnf7, an essential cellular component of endosomal sorting complex required for transport (ESCRT), caused deficiencies in protein de-ubiquitination and autophagy, leading to WCR death. Here we investigated the detailed mechanism leading to larval death by analyzing the ultrastructural changes in midgut enterocytes of WCR treated with double-stranded RNA (ds-DvSnf7). The progressive phases of pathological symptoms caused by DvSnf7-RNAi in enterocytes include: 1) the appearance of irregularly shaped macroautophagic complexes consisting of relatively large lysosomes and multi-lamellar bodies, indicative of failure in autolysosome formation; 2) cell sloughing and loss of apical microvilli, and eventually, 3) massive loss of cellular contents indicating loss of membrane integrity. These data suggest that the critical functions of Snf7 in insect midgut cells demonstrated by the ultrastructural changes in DvSnf7 larval enterocytes underlies the conserved essential function of the ESCRT pathway in autophagy and membrane stability in other organisms.     

Vegetation of trampled habitats in the Plitvice Lakes National Park in Croatia

Abstract

The vegetation communities of the trampled habitats in the Plitvice Lakes National Park were studied during 2005 and 2006. With the numerical classification of the relevés, six clusters were obtained, corresponding to the following specific communities: cluster 1 – ass. Matricario–Polygonetum arenastri– the intensively trampled and grazed habitats; cluster 2 – ass. Matricario–Polygonetum arenastri– the only intensively trampled habitats; cluster 3 – ass. Coronopodo–Polygonetum arenastri– very intensively trampled and grazed farmyards; cluster 4 –Trifolium fragiferum community – the trampled surfaces of moist habitats; cluster 5 – ass. Lolietum perennis– the moderately trampled surfaces of roads and yards; cluster 6 – ass. Prunello–Ranunculetum repentis– trampled surfaces of forest roads. The first three clusters belong to the vegetation of intensively trampled habitats of the class Polygono arenastri–Poetea annuae and the last three clusters belong to moderately trampled habitats of the class Molinio–Arrhenatheretea. In the analysis of the ecological factors it is established that separation of the relevés is influenced most greatly by the trampling intensity observed in the field, and of the Ellenberg indicator values, the most important are light, moisture, soil reaction and temperature. Using the analysis of the plant functional traits it is established that therophytes, annuals, biennials, species resistant to trampling and grazing, neophytes and archeophytes prevail in the intensively trampled habitats. In contrast, hemicryptophytes, perennials, and indigenous plant species prevail in the moderately trampled habitats. Representation of the C-S-R plant functional types shows also that trampling as a disturbance factor has a large influence on the differences in the relevés. In the intensively trampled habitats, there is a large proportion of ruderals, while in the moderately trampled habitats there is a large proportion of competitors.     

Sgo1 is required for co-segregation of sister chromatids during achiasmate meiosis I

The reduction of chromosome number during meiosis is achieved by two successive rounds of chromosome segregation, called meiosis I and meiosis II. While meiosis II is similar to mitosis in that sister kinetochores are bi-oriented and segregate to opposite poles, recombined homologous chromosomes segregate during the first meiotic division. Formation of chiasmata, mono-orientation of sister kinetochores and protection of centromeric cohesion are three major features of meiosis I chromosomes which ensure the reductional nature of chromosome segregation. Here we show that sister chromatids frequently segregate to opposite poles during meiosis I in fission yeast cells that lack both chiasmata and the protector of centromeric cohesion Sgo1. Our data are consistent with the notion that sister kinetochores are frequently bi-oriented in the absence of chiasmata and that Sgo1 prevents equational segregation of sister chromatids during achiasmate meiosis I.Key words: meiosis, chromosome segregation, recombination, kinetochore, Sgo1, fission yeast     

Evidence for Distinct Functions of MRE11 in Arabidopsis Meiosis

The evolutionary conserved Mre11/Rad50/Nbs1 complex functions as one of the guardians of genome integrity in eukaryotes; it is required for the double-strand break repair, meiosis, DNA checkpoint, and telomere maintenance. To better understand the role of the MRE11 gene in Arabidopsis, we performed comparative analysis of several mre11 alleles with respect to genome stability and meiosis. The mre11-4 and mre11-2 alleles presumably produce truncated MRE11 proteins composed of the first 499 and 529 amino acids, respectively. Although the putative MRE11 truncated proteins differ only by 30 amino acids, the mutants exhibited strikingly different phenotypes in regards to growth morphology, genome stability and meiosis. While the mre11-2 mutants are fully fertile and undergo normal meiosis, the mre11-4 plants are sterile due to aberrant repair of meiotic DNA breaks. Structural homology analysis suggests that the T-DNA insertion in the mre11-4 allele probably disrupted the putative RAD50 interaction and/or homodimerization domain, which is assumed to be preserved in mre11-2 allele. Intriguingly, introgression of the atm-2 mutant plant into the mre11-2 background renders the double mutant infertile, a phenotype not observed in either parent line. This data indicate that MRE11 partially compensates for ATM deficiency in meiosis of Arabidopsis.