Genes of the extinct Caucasian bison still roam the Białowieża Forest and are the source of genetic discrepances between Polish and Belarusian populations of the European bison,Bison bonasus

European bison (Bison bonasus) populations from both the Polish (PL) and the Belarusian (BY) sides of the Bia?owie?a Forest represent the Lowland genetic line (LB line) – progeny of the Lowland bison (Bison bonasus bonasus) that inhabited western, central, and south‐eastern Europe in historical times. During the species recovery, one of the founders was a descendant of the extinct Caucasian bison (Bison bonasus caucasicus) and its descendants formed the other genetic line – Lowland–Caucasian (LC). There have been justified suspicions that LB European bison in the former Soviet Union had undergone cross‐mating with the LC line. We performed a comparative genetic analyses on European bison from the BY and PL parts of the Bia?owie?a Forest, the LC line and extinct Caucasian bison, based on a set of 19 microsatellite markers and 1512 bovine single nucleotide polymorphism (SNP) markers, polymorphic in at least one of the studied populations. Although genetic variability (mean allele number and expected heterozygosity) for both populations were similar, the F_ST jack‐knifing and principal component analyses PCA revealed highly significant differences between PL and BY bison from the Bia?owie?a Forest. Examining DNA of the extinct Caucasian bison revealed that at least part of the genetic variants found in the BY, but not the PL, population were of Caucasian origin. The results indicate that the contemporary population of European bison from the BY part of the Bia?owie?a Forest should not be regarded as a LB line. The results also suggest that the actual global population size of the LB line European bison is only a half of its official status. Consideration of the presented results are crucial in determining management actions and policy decisions in order to conserve LB line bison within the Bia?owie?a Forest – its natural refuge. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 752–763.     

Expression of miRNAs involved in phosphate homeostasis and senescence is altered in glyphosate-treated maize

Glyphosate is a systemic, nonselective and most widely used herbicide in the world. The introduction of glyphosate-resistant crops in the mid-1990s resulted in a dramatic increase in the use of glyphosate herbicide making it most widely used herbicide in the world. The average maize yield loss in the field caused by pests is around 20 % but in many regions it is much higher. It is now clear that glyphosate causes broader range of physiological alterations than previously assumed and some plants gain higher level of resistance to glyphosate without the need to use genetic engineering methods. To understand the mechanisms of such heightened resistance we must first know the processes mediating the plants’ death in response to glyphosate treatment. Here, we show that 12 miRNAs, belonging to miR167, miR396, miR159, miR156, miR169, miR444 and miR827 families, are significantly upregulated, and one, miR166, downregulated following glyphosate treatment. These miRNAs have been previously shown to be involved in abiotic stress responses and implicated in senescence. Strikingly, two of the induced miRNAs, miR444 and miR827, have been shown to regulate phosphate transport pathways, which seem to be common for Pi and glyphosate uptake.     

Benthic macroinvertebrates along the Czech part of the Labe and lower section of the Vltava rivers from 1996–2005, with a particular focus on rare and alien species

In the Czech part of the Labe River and the lower part of the Vltava River, we examined if the benthic macroinvertebrate composition changed from 1996 to 2005 due to expected improvements in water quality resulting from socioeconomic changes in the Czech Republic since the 1990s. Special attention was given to rare and alien species. The four biological metrics used (Number of taxa, BMWP, Number of sensitive taxa, and Number of EPT taxa) demonstrated that there was indeed an improvement in water quality as well as a slight improvement of the Labe microhabitats during the investigated period. An increasing Number of taxa over time was observed at most sites. Two main concurrent ecological processes are recently in progress in the Labe: a recovery of native species and an expansion of alien species, some of which are considered invasive. The caddisfly Setodes punctatus and the beetle Pomatinus substriatus, considered as regionally extinct in the Czech Republic until 2005, were rediscovered during our investigations. Findings of the crustacean Hemimysis anomala (invasive) and the chironomids Stenochironomus sp. and Lipiniella sp. were the first records of these taxa in the Czech Republic.     

Three-Dimensional Organization of Troponin on Cardiac Muscle Thin Filaments in the Relaxed State

Muscle contraction is regulated by troponin-tropomyosin, which blocks and unblocks myosin binding sites on actin. To elucidate this regulatory mechanism, the three-dimensional organization of troponin and tropomyosin on the thin filament must be determined. Although tropomyosin is well defined in electron microscopy helical reconstructions of thin filaments, troponin density is mostly lost. Here, we determined troponin organization on native relaxed cardiac muscle thin filaments by applying single particle reconstruction procedures to negatively stained specimens. Multiple reference models led to the same final structure, indicating absence of model bias in the procedure. The new reconstructions clearly showed F-actin, tropomyosin, and troponin densities. At the 25 Å resolution achieved, troponin was considerably better defined than in previous reconstructions. The troponin density closely resembled the shape of troponin crystallographic structures, facilitating detailed interpretation of the electron microscopy density map. The orientation of troponin-T and the troponin core domain established troponin polarity. Density attributable to the troponin-I mobile regulatory domain was positioned where it could hold tropomyosin in its blocking position on actin, thus suggesting the underlying structural basis of thin filament regulation. Our previous understanding of thin filament regulation had been limited to known movements of tropomyosin that sterically block and unblock myosin binding sites on actin. We now show how troponin, the Ca²⁺ sensor, may control these movements, ultimately determining whether muscle contracts or relaxes.     

An Atomic Model of the Tropomyosin Cable on F-actin

Tropomyosin regulates a wide variety of actin filament functions and is best known for the role that it plays together with troponin in controlling muscle activity. For effective performance on actin filaments, adjacent 42-nm-long tropomyosin molecules are joined together by a 9- to 10-residue head-to-tail overlapping domain to form a continuous cable that wraps around the F-actin helix. Yet, despite the apparent simplicity of tropomyosin’s coiled-coil structure and its well-known periodic association with successive actin subunits along F-actin, the structure of the tropomyosin cable on actin is uncertain. This is because the conformation of the overlap region that joins neighboring molecules is poorly understood, thus leaving a significant gap in our understanding of thin-filament structure and regulation. However, recent molecular-dynamics simulations of overlap segments defined their overall shape and provided unique and sufficient cues to model the whole actin-tropomyosin filament assembly in atomic detail. In this study, we show that these MD structures merge seamlessly onto the ends of tropomyosin coiled-coils. Adjacent tropomyosin molecules can then be joined together to provide a comprehensive model of the tropomyosin cable running continuously on F-actin. The resulting complete model presented here describes for the first time (to our knowledge) an atomic-level structure of αα-striated muscle tropomyosin bound to an actin filament that includes the critical overlap domain. Thus, the model provides a structural correlate to evaluate thin-filament mechanics, self-assembly mechanisms, and the effect of disease-causing mutations.     

A novel inhibitor of cytokinin degradation (INCYDE) influences the biochemical parameters and photosynthetic apparatus in NaCl-stressed tomato plants

The effect of 2-chloro-6-(3-methoxyphenyl)aminopurine [inhibitor of cytokinin degradation (INCYDE)] at 10 nM on growth, biochemical and photosynthetic efficiency in sodium chloride (NaCl)-stressed (75, 100 and 150 mM) tomato plants was investigated. NaCl-induced decline in plant vigor index was slightly reversed by both drenching and foliar application of INCYDE. Foliar application of INCYDE significantly increased the flower number in the control and 75 mM NaCl-supplemented plants, while drenching was more effective in 150 mM NaCl-stressed plants. Antioxidant enzymes (peroxidase, catalase and superoxide dismutase) were enhanced in the presence of INCYDE in the control and NaCl-stressed plants. Higher concentration of malondialdehyde (MDA) associated with oxidative (lipid peroxidation) damage in leaf tissue which was evident in the presence of NaCl stress was significantly attenuated with the drenching and foliar application of INCYDE. Regardless of NaCl concentration, application of INCYDE had no significant influence on maximum quantum efficiency of photosystem II. However, the reduced quantum yield of photosystem II and coefficient of photochemical quenching under continuous illumination with actinic light at four intensities (264, 488, 800 and 1,200 µmol m^?2 s^?1) in NaCl-stressed (100 and 150 mM) tomato plants were significantly alleviated by drenching application with INCYDE. Non-photochemical quenching of the singlet excited state of chlorophyll a and relative electron transfer rate were generally higher in INCYDE-treated plants than in the controls. From an agricultural perspective, these findings indicate the potential of INCYDE in protecting plants against NaCl stress and the possibility of enhanced productivity.     

Effect of abiotic stress stimuli on S-nitrosoglutathione reductase in plants

S-nitrosylation of protein cysteine thiol groups has recently emerged as a widespread and important reversible post-translational protein modification, involved in redox signalling pathways of nitric oxide and reactive nitrogen species. S-nitrosoglutathione reductase (GSNOR), member of class III alcohol dehydrogenase family (EC 1.1.1.1), is considered the key enzyme in the catabolism of major low molecular S-nitrosothiol, S-nitrosoglutathione, and hence to control the level of protein S-nitrosylation. Changes of GSNOR activity after exposure to different abiotic stress conditions, including low and high temperature, continuous dark and de-etiolation, and mechanical injury, were investigated in important agricultural plants. Significantly higher GSNOR activity was found under normal conditions in leaves of Cucumis spp. genotype sensitive to biotrophic pathogen Golovinomyces cichoracearum. GSNOR activity was generally increased in all studied plants by all types of stress conditions. Strong down-regulation of GSNOR was observed in hypocotyls of etiolated pea plants, which did not recover to values of green plants even 168 h after the transfer of etiolated plants to normal light regime. These results point to important role of GSNOR during normal plant development and in plant responses to several types of abiotic stress conditions.