Multimarker response to salinity stress in two estuarine bivalves of different genetic diversity: Mya arenaria and Limecola balthica from the Gulf of Gdańsk (southern Baltic Sea)

The estuarine bivalves Limecola balthica and Mya arenaria are common inhabitants of marine soft bottom habitats in the Northern Hemisphere. Both species are able to live under a wide range of environmental conditions including variable salinity. However, in L. balthica there is high genetic variability, and populations are often genetically adapted to local conditions. By contrast, genetic diversity in M. arenaria is low across the species’ geographic range, which attests to acclimatization to different conditions. We hypothesized that individuals of M. arenaria should perform better under osmotic stress. We tested this hypothesis by performing a 5‐week experiment that exposed individuals of both clam species to hypo‐ and hyperosmotic conditions. A multiple biomarker approach that included physiological, biochemical, and histological markers was used to assess bivalve performance. Exposure to the different salinities induced biological responses that particularly affected respiratory activity in both species tested, but these responses were much more pronounced in individuals of L. balthica. The results confirmed the hypothesis that the phenotypic plasticity of M. arenaria was more pronounced and reflected a different strategy of adapting to heterogeneous habitats.     

Response of <Emphasis Type="Italic">Dionaea muscipula</Emphasis> J. Ellis to light stress in in vitro: physiological study

Hyperhydricity can cause significant economic loss for the micro-propagation industry that produces blueberry. In order to predict and control the occurrence of hyperhydricity, better understanding of the anatomical and physiological features of hyperhydric plantlets is required. In this study, we investigated the ultrastructural and physiological changes associated with hyperhydric blueberry plantlets. Compared to normal plantlets, hyperhydric plantlets exhibited reduced cell wall thickness, damaged membrane and guard cell structure, decreased number of mitochondria and starch granule, higher cell vacuolation, more intercellular spaces, and collapse of vascular tissues. In addition, excessive accumulation of reactive oxygen species (ROS) and ethylene, decreased stomatal aperture and water loss, as well as abnormity of stomatal movement were also evident in the hyperhydric plantlets. The results suggested that excessive ethylene and ROS produced in response to the stress arising from in vitro culture could lead to abnormal stomatal closure, causing the accumulation of water in the tissues. This would lead to subsequent induction of oxidative stress (due to hypoxia) and cell damage, especially guard cell structure, eventually giving rise to the symptoms of hyperhydricity. Reducing the content of ethylene and ROS, and protecting the structure and function of the stomata could be considered as potential strategies for inhibiting hyperhydricity or restoring the hyperhydric plants to their normal state.     

TRENDS IN THE EVOLUTION OF THE EUGLENID PELLICLE

Abstract Trends in the evolution of the euglenid pellicle were described using phylogenetic methods on 18S rDNA, morphological, and combined data from 25 mostly phototrophic taxa. The tree topology from a total‐evidence analysis formed a template for a synthetic tree that took into account conflicting results derived from the partitioned datasets. Pellicle character states that can only be observed with the assistance of transmission and scanning electron microscopy were phylogenetically mapped onto the synthetic tree to test a set of previously established homology statements (inferences made independently from a cladogram). The results permitted us to more confidently infer the ancestral‐derived polarities of character state transformations and provided a framework for understanding the key cytoskeletal innovations associated with the evolution of phototrophic euglenids. We specifically addressed the character evolution of (1) the maximum number of pellicle strips around the cell periphery; (2) the patterns of terminating strips near the cell posterior end; (3) the substructural morphology of pellicle strips; (4) the morphology of the cell posterior tip; and (5) patterns of pellicle pores on the cell surface.     

Intra-seasonal variation in zooplankton availability,chick diet and breeding performance of a high Arctic planktivorous seabird

Different phenological responses to climate changes by species representing preys and predators may lead to mismatch between functionally dependent components of an ecosystem, with important effects on its structure and functioning. Here, we investigate within-season variation in zooplankton availability, chick diet composition and breeding performance of a small planktivorous seabird, the little auk (Alle alle) in two large colonies in Hornsund and Magdalenefjorden, Spitsbergen, differing in synchrony of breeding (11-day vs. 22-day hatching period, respectively). Assuming similar zooplankton phenology and existing differences in duration of the little auk breeding period, we expected lower availability of the preferred food in the less synchronized colony in Magdalenefjorden and in consequence a negative effect on nestling body mass and survival. We found that in both colonies Calanus glacialis (copepodite stage CV) was the most important prey item in the chick diet making up 68–87 % of the biomass and energy of all prey items. The only exception was the end of the chick-rearing period in Magdalenefjorden, when contribution of this prey item was significantly lower (24–26 %). Thus, late breeders in Magdalenefjorden were apparently mismatched regarding C. glacialis CV availability. However, the hatching date did not affect birds fitness (reproductive output and chick pre-fledging mass) significantly. Results of our study indicate that little auks breeding on Spitsbergen can respond to a wide range of environmental conditions and prey availabilities through the plasticity of their foraging behaviour, which may help them to maintain their optimum fitness level in changing and unpredictable environments.     

Genome Analysis Traces Regional Dispersal of Rice in Taiwan and Southeast Asia

The dispersal of rice (Oryza sativa) following domestication influenced massive social and cultural changes across South, East, and Southeast (SE) Asia. The history of dispersal across islands of SE Asia, and the role of Taiwan and the Austronesian expansion in this process remain largely unresolved. Here, we reconstructed the routes of dispersal of O. sativa ssp. japonica rice to Taiwan and the northern Philippines using whole-genome resequencing of indigenous rice landraces coupled with archaeological and paleoclimate data. Our results indicate that japonica rice found in the northern Philippines diverged from Indonesian landraces as early as 3,500 years before present (BP). In contrast, rice cultivated by the indigenous peoples of the Taiwanese mountains has complex origins. It comprises two distinct populations, each best explained as a result of admixture between temperate japonica that presumably came from northeast Asia, and tropical japonica from the northern Philippines and mainland SE Asia, respectively. We find that the temperate japonica component of these indigenous Taiwan populations diverged from northeast Asia subpopulations at about 2,600 BP, whereas gene flow from the northern Philippines had begun before ∼1,300  BP. This coincides with a period of intensified trade established across the South China Sea. Finally, we find evidence for positive selection acting on distinct genomic regions in different rice subpopulations, indicating local adaptation associated with the spread of japonica rice.     

The intelligentsia informed habitus in social distance strategies of Polish migrants in the UK

Antagonism and conflict within newly resident UK Polish migrants has been typically related to labour market competition. Without denying the relevance of this argument, we argue that explanations of antagonism within the Polish community should also take into account the role of a Polish intelligentsia habitus. This habitus provides a repertoire of available discursive strategies used for interpreting antagonistic and “risk” situations both in Poland and among Poles abroad. It is argued that not only can this intelligentsia habitus critically legitimize intergroup inequalities in status and symbolic power but also may impact on the patterns of a migrant’s integration, linkage to social networks, access to different capital resources, and interactions with the indigenous population.     

Optimal closed-loop deep brain stimulation using multiple independently controlled contacts

Deep brain stimulation (DBS) is a well-established treatment option for a variety of neurological disorders, including Parkinson’s disease and essential tremor. The symptoms of these disorders are known to be associated with pathological synchronous neural activity in the basal ganglia and thalamus. It is hypothesised that DBS acts to desynchronise this activity, leading to an overall reduction in symptoms. Electrodes with multiple independently controllable contacts are a recent development in DBS technology which have the potential to target one or more pathological regions with greater precision, reducing side effects and potentially increasing both the efficacy and efficiency of the treatment. The increased complexity of these systems, however, motivates the need to understand the effects of DBS when applied to multiple regions or neural populations within the brain. On the basis of a theoretical model, our paper addresses the question of how to best apply DBS to multiple neural populations to maximally desynchronise brain activity. Central to this are analytical expressions, which we derive, that predict how the symptom severity should change when stimulation is applied. Using these expressions, we construct a closed-loop DBS strategy describing how stimulation should be delivered to individual contacts using the phases and amplitudes of feedback signals. We simulate our method and compare it against two others found in the literature: coordinated reset and phase-locked stimulation. We also investigate the conditions for which our strategy is expected to yield the most benefit.     

Structure of the active subunit of the yeast exosome core, Rrp44: diverse modes of substrate recruitment in the RNase II nuclease family

The eukaryotic exosome is a macromolecular complex essential for RNA processing and decay. It has recently been shown that the RNase activity of the yeast exosome core can be mapped to a single subunit, Rrp44, which processively degrades single-stranded RNAs as well as RNAs containing secondary structures. Here we present the 2.3 A resolution crystal structure of S. cerevisiae Rrp44 in complex with single-stranded RNA. Although Rrp44 has a linear domain organization similar to bacterial RNase II, in three dimensions the domains have a different arrangement. The three domains of the classical nucleic-acid-binding OB fold are positioned on the catalytic domain such that the RNA-binding path observed in RNase II is occluded. Instead, RNA is threaded to the catalytic site via an alternative route suggesting a mechanism for RNA-duplex unwinding. The structure provides a molecular rationale for the observed biochemical properties of the RNase R family of nucleases.     

Type II secretory pathway for surface secretion of DraD invasin from the uropathogenic Escherichia coli Dr+ strain

The virulence of the uropathogenic Escherichia coli Dr(+) IH11128 strain is associated with the presence of Dr fimbrial structures and a DraD invasin which can act as a fimbrial capping domain at the bacterial cell surface. However, a recent study suggests that the DraD protein is surface exposed in two forms: fimbria associated and fimbria nonassociated (prone to interaction with the N-terminal extension of the DraE protein located on the fimbrial tip). The actual mechanism of DraD surface secretion is presently unknown. We identified a previously unrecognized type II secretory pathway (secreton) in the uropathogenic E. coli Dr(+) strain which is well conserved among gram-negative bacteria and used mainly for secretion of virulence determinants. An active secreton is composed of 12 to 15 different proteins, among which GspD functions as an outer-membrane channel to permit extrusion of proteins in a folded state. Therefore, we inactivated the pathway by inserting the group II intron into a gspD gene of the type II secretion machinery by site-specific recombination. DraD secretion by the E. coli Dr(+) and gspD mutant strains was determined by immunofluorescence microscopy (with antibodies raised against DraD) and an assay of cell binding between bacteria and HeLa cells. The specificity of DraD-mediated bacterial binding for the integrin receptor was confirmed by examination of the adhesion of DraD-coated beads to HeLa cells in the presence and absence of alpha(5)beta(1) monoclonal antibodies. The investigations that we performed showed that type II secretion in E. coli Dr(+) strains leads to DraD translocation at the bacterial cell surfaces.