Zsolt Szilágyi

Eleven novel sep genes of Schizosaccharomyces pombe required for efficient cell separation and sexual differentiation

Genetic analysis of 20 sterile mutants prone to form hyphae revealed 11 novel ste genes (sep6 to sep16) of Schizosaccharomyces pombe. None of the mutants was completely mycelial. Most mutants formed branching hyphae and showed normal septation. Aberrant septal structures and actin distribution were seen only at 36°C. sep9‐307, sep14‐576 and sep15‐598 showed genetic interactions with sep1‐1, a mutation in a forkhead transcription factor homologue. Additional genetic interactions were detected between sep6‐194, sep15‐598 and cdc16‐116, a mutant allele of an anaphase modulator of p34cdc2. sep9‐307 and sep15‐598 caused dikaryosis in wee1− background. In mating and sporulation tests, sep6−, sep7−, sep9−, sep10−, sep11− and sep15− proved to be defective in conjugation only, whereas sep8−, sep13− and sep16− were also defective in meiosis‐sporulation. sep12− and sep14− were only partially sterile. All mutants could produce M‐factor but sep8−, sep11−, sep15− and sep16− were defective in P‐factor production. The mutations in sep8, sep11 and sep16 suppressed the pat1‐114‐driven meiosis. All mutants were sensitive to the presence of higher concentrations of chloride in the medium and to short heat shocks. The diversity of the mutant phenotypes and the pleiotropic effects of the mutations suggest that these sep genes might act in, or interact with, a multiple overlapping network of regulatory modules. Copyright

Genomic expression patterns in cell separation mutants of Schizosaccharomyces pombe defective in the genes sep10 ( + ) and sep15 ( + ) coding for the Mediator subunits Med31 and Med8.

Cell division is controlled by a complex network involving regulated transcription of genes and postranslational modification of proteins. The aim of this study is to demonstrate that the Mediator complex, a general regulator of transcription, is involved in the regulation of the second phase (cell separation) of cell division of the fission yeast Schizosaccharomyces pombe. In previous studies we have found that the fission yeast cell separation genes sep10+ and sep15+ code for proteins (Med31 and Med8) associated with the Mediator complex. Here, we show by genome-wide gene expression profiling of mutants defective in these genes that both Med8 and Med31 control large, partially overlapping sets of genes scattered over the entire genome and involved in diverse biological functions. Six cell separation genes controlled by the transcription factors Sep1 and Ace2 are among the target genes. Since neither sep1+ nor ace2+ is affected in the mutant cells, we propose that the Med8 and Med31 proteins act as coactivators of the Sep1-Ace2-dependent cell separation genes. The results also indicate that the subunits of Mediator may contribute to the coordination of cellular processes by fine-tuning of the expression of larger sets of genes.

Marker construction and cloning of a cut1-like sequence with ARS activity in the fission yeast Schizosaccharomyces japonicus

The dimorphic fission yeast Schizosaccharomyces japonicus has proved to be an excellent experimental model for the investigation of the eukaryotic cell. Here we show that it has a haplontic life cycle, in which the diploid phase is confined to the zygote. To make it amenable to genetic and molecular analysis, we generated genetic markers and cloned a genomic sequence which acts as ars when integrated into a plasmid. Diploids suitable for testing complementation and recombination between markers can be formed by protoplast fusion. The complementation tests and the recombination frequencies determined in octads of spores identified 28 non‐allelic groups (genes) of mutations of the auxotrophic and mycelium‐negative mutants. Two groups of linked markers were also identified. The cloned fragment, which expresses ars activity, encodes a putative amino acid sequence highly similar to a conserved domain of proteins Cut1 (Schizosaccharomyces pombe), BimB (Aspergillus nidulans) and Esp1 (Saccharomyces cerevisiae). Copyright

The involvement of the Schizosaccharomyces pombe sep9/spt8+ gene in the regulation of septum cleavage

Schizosaccharomyces cells divide by medial septation, followed by enzymatic degradation of parts of the septum (septum cleavage) to allow the sister cells to separate from each other. In a previous study we found that the cell separation mutant sep9-307 was defective in a gene that encodes a protein highly similar in sequence to the Saccharomyces cerevisiae protein Spt8, a subunit of the SAGA complex. Here, we show that the sep9-307 mutation causes a frameshift in translation. The deletion of sep9(+) is not lethal but abolishes normal septum cleavage by reducing the activity of ace2(+), a gene coding for a transcription factor of numerous genes producing proteins for septum cleavage. Indirect evidence indicates that Sep9 might also act directly in the transcription of certain target genes (e.g. eng1(+)) of this regulator. sep9-307 is synthetically lethal with mutations in the cell separation genes sep11/med18(+) and sep15/med8(+), which encode subunits of the general transcription factor mediator. Heterologous expression of SPT8 and the putative Schizosaccharomyces japonicus sep9(+) orthologue cannot substitute for sep9(+). Both Spt8 and the fission yeast proteins have highly acidic (74-76 amino-acid long) N-terminal regions with no sequence conservation.

A társadalmi tér használata a kecskeméti multifunkcionális elit gyakorlata szerint, 1920–1940

To explore the Kecskemet elite of the interwar period, a concept of elite was formulated that profoundly differs from previous approaches. A local elite is a formation of a societal group which is organised on the basis of family relations and financial assets, due to which it possessed a high, socially visible or latent, standing and thus owned politically organised or latent power. The elite asserted this power within the local setting by influencing the whole or part of the local community. The structure of the local elite varies by region or by settlement levels (city, town, village, etc.) in accordance with the differences within local societies and how they create elites or the administrative ranking of a settlement which determines varying quantitative and qualitative opportunities for people to assume, or rise to, elite positions. Functionally, the local elite consists of three sub-groups: a political elite, controlling the town, an economic elite that controls commercial matters and a societal elite that informally regulates the access to elite circles, often through family relations. These three elite sub-groups often overlap and generally meet in various societal settings. As these subgroups belong to at least two elite circles where they meet, we call them a multifunctional elite.The multifunctional elite of Kecskemet consisted of 368 members in the period under investigation and accounted for about 30–40% of the total town elite. The occupational composition showed certain changes during this period: The ratio of merchants decreased by almost 50%, while the ratio of intellectuals increased by about 25%. In addition, a fast and spectacular growth in property ownership by the elite is discernible which was mainly due to real estate and land speculation during the Great Depression. The value of the multifunctional elite’s real estate increased by 16% in the period from the 1920s until the 1930s.An examination of social space revealed that the elite lived within the historical town core. Craftsmen and landowners showed occupational similarities in social topographic terms: Their group and their activities were not as closely linked to space as those of the intellectuals, i. e. their spatial characteristics were not significant. The social space of merchants was adapted to the economic space structure of the town, while the social space of civil servants and intellectuals followed the spatial pattern of institutions and offices. This tight pattern must be seen in the context of the changes in physical and social space which occurred in the 2nd half of the 19th century. The groups of merchants and intellectuals, and the elites that subsequently arose from them, emerged within those locations. During these processes, one of the main determining factors was the property-income status of individuals. The streets and squares of outstanding historic prestige had a decisive impact on the spatial differentiation of the elites; similarly, the influence of relationships maintained with neighbours, friends or relatives was important.

Város–tanya-kapcsolat a Horthy-kori Kecskeméten

Tanyas are isolated cottage-style farmsteads scattered around a central town, sometimes at a considerable distance, often 5-10 km, but sometimes up to 25 km. They are mainly distinguished by whether one could reach the town from them in a day and return or not. During the period between the two World Wars, Kecskemet was the market town where the ‘tanya’ zones, which concentrically surrounded the town, were the origin of significant domestically and internationally demanded fruit and vegetable cultivation – all of which contributed to a continuously extending and prospering farmland cultivation. From the second half of the 1920s, the booming economy induced profound changes in several fields and the category of ‘tanya’ settlements slowly ceased to be used for statistical or research purposes. Between the 1920s and the 1930s, more than 90 per cent of the tanyas in the Kecskemet area were separate settlements. The concept of the tanyas was to make a living independently from a town and not primarily how to remain related to the town. Nevertheless the tanyas were symbiotically linked to the town, because there was a very intensive economic relation as produce was regularly brought to market in Kecskemet and central services (shops, schools, doctors) were used. In addition, about 5–7 per cent of the tanya population moved to town houses in winter. Thus tanya families lived in separation, but not in isolation from the town. They were just not part of town life for most of the year. This study suggests that socio-historical and historical-geographical surveys – in contrast to currently used, mostly statistical methods – should treat in-towners and out-towners separately. In addition, adequate attention should be paid to the fact that the semi-peripherical and the peripherical town-regions were not sharply separated from each other in all economic and social aspects. Archive research and interviews with members of the older generation suggest that there was much differentiation between tanyas according to their distance to the town of Kecskemet. In conclusion it is pointed out that most of the questions raised by historical-geographical research discussed here require innovative approaches and methods. They need the utilisation of additional resources such as archives, preferably digitalised archives, and interviews revealing historical experiences.