Biochemical Activities of the Wiskott-Aldrich Syndrome Homology Region 2 Domains of Sarcomere Length Short (SALS) Protein

Drosophila melanogaster sarcomere length short (SALS) is a recently identified Wiskott-Aldrich syndrome protein homology 2 (WH2) domain protein involved in skeletal muscle thin filament regulation. SALS was shown to be important for the establishment of the proper length and organization of sarcomeric actin filaments. Here, we present the first detailed characterization of the biochemical activities of the tandem WH2 domains of SALS (SALS-WH2). Our results revealed that SALS-WH2 binds both monomeric and filamentous actin and shifts the monomer-filament equilibrium toward the monomeric actin. In addition, SALS-WH2 can bind to but fails to depolymerize phalloidin- or jasplakinolide-bound actin filaments. These interactions endow SALS-WH2 with the following two major activities in the regulation of actin dynamics: SALS-WH2 sequesters actin monomers into non-polymerizable complexes and enhances actin filament disassembly by severing, which is modulated by tropomyosin. We also show that profilin does not influence the activities of the WH2 domains of SALS in actin dynamics. In conclusion, the tandem WH2 domains of SALS are multifunctional regulators of actin dynamics. Our findings suggest that the activities of the WH2 domains do not reconstitute the presumed biological function of the full-length protein. Consequently, the interactions of the WH2 domains of SALS with actin must be tuned in the cellular context by other modules of the protein and/or sarcomeric components for its proper functioning.     

Effect of Ca/Mg ions ratio on copper accumulation, photosynthetic activity and growth of Cu2+-treated Salix viminalis L. ‘Cannabina’

The aim of the study was to the assess the influence of Ca/Mg ions ratio on the photosynthetic activity of Salix viminalis L. ??Cannabina?? plants cultivated in medium enriched with Cu(NO₃)₂. The experiment was conducted in controlled conditions in a phytotron for 21 days; hence the early plant response was tested. Plants were cultivated with different Ca/Mg ions ratios, i.e. (4:1)_l, (4:1)_h, and 1:10. Plants were additionally treated with Cu(NO₃)₂ at 1, 2, and 3 mM concentration in cultivation medium. Net photosynthetic rate, stomatal conductance and transpiration were measured after the first, second and third week of cultivation. Additionally, chlorophyll content, leaf morphology, root biomass and copper accumulation in leaves and roots were investigated. The investigations revealed differences in plant response to particular treatments ?? differences in Cu accumulation for particular Ca/Mg ions ratios were detected. It seems that plants are adapted to high Cu²⁺ concentrations, when 1:10 Ca/Mg ions ratio is applied. The highest Cu accumulation in roots was noted for plants fertilized with 1:10 Ca/Mg ions ratio, together with high Cu translocation to above-ground plant organs, which suggests its higher potential in phytoremediation.     

Intracellular Calcium Deficits in Drosophila Cholinergic Neurons Expressing Wild Type or FAD-Mutant Presenilin

Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation.     

Reconstruction of the proximal ends of retiolitid rhabdosomes (Graptolithina) from the Upper Wenlock and the Lower Ludlow

Detailed study of the ultrastructures on the cortical lists of retiolitids occurring after the lundgreni event has been undertaken. The extremely well preserved material from the Go?dap borehole of Poland (Baltica) enables classification of clathrial lists into two types—with single and double seams. Significantly different seam development is observed between two groups of retiolitids occurring before and after the lundgreni event. The study of seams and increments on the lists enables reconstruction of the membrane arrangement of the rhabdosomes. Reconstruction of the proximal ends, the arrangement of the ancora umbrella, and the layout of the proximal ventral and lateral orifices of five genera, Neogothograptus, Holoretiolites, Plectograptus, Spinograptus, and Quattuorgraptus n. gen., is presented. The new genus Quattuorgraptus is separated from Spinograptus because of the different development of the ancora umbrella and the width of the lateral walls of the rhabdosome.     

SorCS2 Controls Functional Expression of Amino Acid Transporter EAAT3 and Protects Neurons from Oxidative Stress and Epilepsy-Induced Pathology

1. Download high-res image (226KB)
2. Download full-size image

     

Physiological and Molecular Background of Maize Cold-Tolerance Enhancement with S-methylmethionine Salicylate

Low temperature is amongst the most influential abiotic stress factors, having deep impact on plant growth, yield and productivity. Studies on beneficial effects of certain biologically active substances, S-methylmethionine (SMM) and salicylic acid (SA) have provided a lot of valuable information regarding their role to counteract harmful effects of environmental stresses such as chilling. To obtain a more complex and stable defence compound with an extended range of stress-protective effect, the new derivative S-methylmethionine salicylate (MMS) was synthesised from the natural, biologically active substances SMM and SA. Since both original materials have complex stress-protective roles, the new compound was expected to combine the effects of original substances and to stabilise the unstable SMM in the new compound, thus providing an extended stress tolerance. Photosynthetic efficiency and accumulation of stress-related metabolites (polyamines and flavonoids) were measured in chilled and control plants, with and without MMS pretreatment, and expression changes of several genes involved in the cold stress response were analysed by quantitative real-time PCR (RT-qPCR) and a detailed microarray study. Our data show how the MMS combines the effect of SMM and SA on molecular level, causing numerous changes in the gene expression pattern and metabolite content. MMS gives rise to a better physiological condition, thus it could provide an alternative, environmental friendly way to enhance the plants defence mechanisms against stressors. As MMS is more stable than SMM, it promises easier, more long-lasting and more cost-effective usage in agriculture, with a complementing effect of SA.