Transcriptomic Studies Reveal that the Rhizobium leguminosarum Serine/Threonine Protein Phosphatase PssZ has a Role in the Synthesis of Cell-Surface Components, Nutrient Utilization, and Other Cellular Processes

Rhizobium leguminosarum bv. trifolii is a soil bacterium capable of establishing symbiotic associations with clover plants (Trifolium spp.). Surface polysaccharides, transport systems, and extracellular components synthesized by this bacterium are required for both the adaptation to changing environmental conditions and successful infection of host plant roots. The pssZ gene located in the Pss-I region, which is involved in the synthesis of extracellular polysaccharide, encodes a protein belonging to the group of serine/threonine protein phosphatases. In this study, a comparative transcriptomic analysis of R. leguminosarum bv. trifolii wild-type strain Rt24.2 and its derivative Rt297 carrying a pssZ mutation was performed. RNA-Seq data identified a large number of genes differentially expressed in these two backgrounds. Transcriptome profiling of the pssZ mutant revealed a role of the PssZ protein in several cellular processes, including cell signalling, transcription regulation, synthesis of cell-surface polysaccharides and components, and bacterial metabolism. In addition, we show that inactivation of pssZ affects the rhizobial ability to grow in the presence of different sugars and at various temperatures, as well as the production of different surface polysaccharides. In conclusion, our results identified a set of genes whose expression was affected by PssZ and confirmed the important role of this protein in the rhizobial regulatory networ

Hanks-Type Serine/Threonine Protein Kinases and Phosphatases in Bacteria: Roles in Signaling and Adaptation to Various Environments

Reversible phosphorylation is a key mechanism that regulates many cellular processes in prokaryotes and eukaryotes. In prokaryotes, signal transduction includes two-component signaling systems, which involve a membrane sensor histidine kinase and a cognate DNA-binding response regulator. Several recent studies indicate that alternative regulatory pathways controlled by Hanks-type serine/threonine kinases (STKs) and serine/threonine phosphatases (STPs) also play an essential role in regulation of many different processes in bacteria, such as growth and cell division, cell wall biosynthesis, sporulation, biofilm formation, stress response, metabolic and developmental processes, as well as interactions (either pathogenic or symbiotic) with higher host organisms. Since these enzymes are not DNA-binding proteins, they exert the regulatory role via post-translational modifications of their protein targets. In this review, we summarize the current knowledge of STKs and STPs, and discuss how these enzymes mediate gene expression in prokaryotes. Many studies indicate that regulatory systems based on Hanks-type STKs and STPs play an essential role in the regulation of various cellular processes, by reversibly phosphorylating many protein targets, among them several regulatory proteins of other signaling cascades. These data show high complexity of bacterial regulatory network, in which the crosstalk between STK/STP signaling enzymes, components of TCSs, and the translational machinery occurs. In this regulation, the STK/STP systems have been proved to play important roles

Mutation in the pssZ Gene Negatively Impacts Exopolysaccharide Synthesis, Surface Properties, and Symbiosis of Rhizobium leguminosarum bv. trifolii with Clover

Rhizobium leguminosarum bv. trifolii is a soil bacterium capable of establishing a nitrogen-fixing symbiosis with clover plants (Trifolium spp.). This bacterium secretes large amounts of acidic exopolysaccharide (EPS), which plays an essential role in the symbiotic interaction with the host plant. This polymer is biosynthesized by a multi-enzymatic complex located in the bacterial inner membrane, whose components are encoded by a large chromosomal gene cluster, called Pss-I. In this study, we characterize R. leguminosarum bv. trifolii strain Rt297 that harbors a Tn5 transposon insertion located in the pssZ gene from the Pss-I region. This gene codes for a protein that shares high identity with bacterial serine/threonine protein phosphatases. We demonstrated that the pssZ mutation causes pleiotropic effects in rhizobial cells. Strain Rt297 exhibited several physiological and symbiotic defects, such as lack of EPS production, reduced growth kinetics and motility, altered cell-surface properties, and failure to infect the host plant. These data indicate that the protein encoded by the pssZ gene is indispensable for EPS synthesis, but also required for proper functioning of R. leguminosarum bv. trifolii cells.Polish National Science Centre grant no. DEC-2012/07/B/NZ1/0009

Societal education and the education divide in European identity, 1992-2015

The fact that highly educated individuals are significantly more likely to self-identify as Europeans than those with lower levels of educational attainment is one of the most robust findings in the scholarship on individual Europeanization. Previous work also shows that this cleavage in supranational identification varies cross-nationally and over time. We contribute to the existing literature by examining the country-level, socio-structural conditions that influence the education cleavage. Focusing on how the educational environment influences identity formation, we test two divergent predictions of how societal education—i.e. the average national level of educational attainment—shapes the cleavage between individuals of differing education levels with respect to their self-identification as European. According to Welzel’s (2013) ‘cross-fertilization approach’, societal education should widen the education divide. By contrast, our alternative ‘cross-attenuating approach’ posits that societal education should instead help to close it. Using a cross-national time-series dataset that includes 28 EU member states and 28 Eurobarometers covering 1992–2015, as well as between–within multilevel models, we find a significantly narrower education cleavage in countries where societal education increased the most during the period of our study. This result provides strong support for the cross-attenuating approach presented here. We theorize that societal education helps to narrow the individual-level education cleavage through a discursive and a network mechanism

Domestic transnationalism and the formation of pro-European sentiments

Increasingly, research on attitudes towards the European project focuses on transnational practices. This article furthers the transnational approach by offering the first systematic analysis of how domestic transnationalism - i.e. transnational practices conducted in the home country - influences the formation of pro-European sentiments. We argue that domestic transnational activities foster recognition of common, transnational interests and identities that support the European integration project. Using a 2013 Eurobarometer, we show the distinct need to pay attention to domestic transnationalism. Individuals engaging in more domestic transnational activities display more pro-European sentiments in four of our five dependent variables. Moreover, the effect of domestic transnationalism is particularly intense among less-educated citizens.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors thank the German Volkswagen Foundation (Grant No: 88-260 2) for their generous support