H3K56me3 is a novel, conserved heterochromatic mark that largely but not completely overlaps with H3K9me3 in both regulation and localization.

Histone lysine (K) methylation has been shown to play a fundamental role in modulating chromatin architecture and regulation of gene expression. Here we report on the identification of histone H3K56, located at the pivotal, nucleosome DNA entry/exit point, as a novel methylation site that is evolutionary conserved. We identify trimethylation of H3K56 (H3K56me3) as a modification that is present during all cell cycle phases, with the exception of S-phase, where it is underrepresented on chromatin. H3K56me3 is a novel heterochromatin mark, since it is enriched at pericentromeres but not telomeres and is thereby similar, but not identical, to the localization of H3K9me3 and H4K20me3. Possibly due to H3 sequence similarities, Suv39h enzymes, responsible for trimethylation of H3K9, also affect methylation of H3K56. Similarly, we demonstrate that trimethylation of H3K56 is removed by members of the JMJD2 family of demethylases that also target H3K9me3. Furthermore, we identify and characterize mouse mJmjd2E and its human homolog hKDM4L as novel, functionally active enzymes that catalyze the removal of two methyl groups from trimethylated H3K9 and K56. H3K56me3 is also found in C. elegans, where it co-localizes with H3K9me3 in most, but not all, tissues. Taken together, our findings raise interesting questions regarding how methylation of H3K9 and H3K56 is regulated in different organisms and their functional roles in heterochromatin formation and/or maintenance

Boron Stress Responsive MicroRNAs and Their Targets in Barley

Boron stress is an environmental factor affecting plant development and production. Recently, microRNAs (miRNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. In this study, miRNAs associated with boron stress were identified and characterized in barley. miRNA profiles were also comparatively analyzed between root and leave samples. A total of 31 known and 3 new miRNAs were identified in barley; 25 of them were found to respond to boron treatment. Several miRNAs were expressed in a tissue specific manner; for example, miR156d, miR171a, miR397, and miR444a were only detected in leaves. Additionally, a total of 934 barley transcripts were found to be specifically targeted and degraded by miRNAs. In silico analysis of miRNA target genes demonstrated that many miRNA targets are conserved transcription factors such as Squamosa promoter-binding protein, Auxin response factor (ARF), and the MYB transcription factor family. A majority of these targets were responsible for plant growth and response to environmental changes. We also propose that some of the miRNAs in barley such as miRNA408 might play critical roles against boron exposure. In conclusion, barley may use several pathways and cellular processes targeted by miRNAs to cope with boron stress

Dvopulsni sustav za isporuku amoksicilina: Pokušaj sprečavanja bakterijske rezistencije na antibiotike

Bearing in mind the present scenario of the increasing biological tolerance of bacteria against antibiotics, a time controlled two pulse dosage form of amoxicillin was developed. The compression coating inlay tablet approach was used to deliver the drug in two pulses to different parts of the GIT after a well defined lag time between the two releases. This was made possible by formulating a core containing one of the two drug fractions (intended to be delivered as the second pulse), which was spray coated with a suspension of ethyl cellulose and a hydrophilic but water insoluble agent as a pore former (microcrystalline cellulose). Coating of 1 up to 5 % (m/m) was applied over the core tablet, giving a corresponding lag of 3, 5, 7 and 12 h. Increasing the level of coating led to retardation of the water uptake capacity of the core, leading to prolongation of the lag time. Microcrystalline cellulose was used as a hydrophilic but water insoluble porosity modifier in the barrier layer, varying the concentration of which had a significant effect on shortening or prolongation of the lag time. This coated system was further partially compression coated with the remaining drug fraction (to be released as the first immediate release pulse) with a disintegrant, giving a final tablet. The core tablet and the final two pulse inlay tablet were further investigated for the in vitro performance.Zbog sve učestalije pojave rezistencije bakterija na antibiotike, razvijen je dvopulsni sustav s vremenskom kontrolom za isporuku amoksicilina. Sustav čine slojevite tablete s obloženim slojem dobivenim metodom kompresije, koji omogućavaju isporuku lijeka u dva pulsa u različite dijelove gastrointestinalnog trakta, s utvrđenom odgodom između dva oslobađanja. Ovakav način oslobađanja postignut je s pripravkom koji u jezgri tablete sadrži jednu frakciju lijeka (koja se oslobađa kao drugi puls), a u oblozi drugu. Obloženi dio dobiven je sprejanjem sa suspenzijom etilceluloze i hidrofilnog, ali vodonetopljivog sredstva koji tvori pore (mikrokristalinična celuloza). Oblaganje sa slojem koji čini 1 do 5 % (m/m) mase jezgre postignut je vremenski odmak drugog pulsa od 3, 5, 7 i 12 h. Povećanjem mase obložnog sloja smanjuje se kapacitet prodiranja vode u jezgru tablete, što produljuje vrijeme drugog pulsa. Mikrokristalinična celuloza uporijebljena je kao hidrofilno, vodonetopljivo sredstvo za kotrolu poroznosti u barijernom sloju. Promjena koncentracije celuloze značajno je utjecala na skraćenje ili produljenje vremenskog odmaka. Obloženi sustav je potom djelomično obložen s preostalom frakcijom lijeka (koja se oslobađa odmah u prvom pulsu) pomiješanom s dezintegratorom. Tableta s jezgrom i dvopulsna slojevita tableta ispitivane su in vitro

Calmodulin-like protein AtCML3 mediates dimerization of peroxisomal processing protease AtDEG15 and contributes to normal peroxisome metabolism

Matrix enzymes are imported into peroxisomes and glyoxysomes, a subclass of peroxisomes involved in lipid mobilization. Two peroxisomal targeting signals (PTS), the C-terminal PTS1 and the N-terminal PTS2, mediate the translocation of proteins into the organelle. PTS2 processing upon import is conserved in higher eukaryotes, and in watermelon the glyoxysomal processing protease (GPP) was shown to catalyse PTS2 processing. GPP and its ortholog, the peroxisomal DEG protease from Arabidopsis thaliana (AtDEG15), belong to the Deg/HtrA family of ATP-independent serine proteases with Escherichia coli DegP as their prototype. GPP existes in monomeric and dimeric forms. Their equilibrium is shifted towards the monomer upon Ca(2+)-removal and towards the dimer upon Ca(2+)-addition, which is accompanied by a change in substrate specificity from a general protease (monomer) to the specific cleavage of the PTS2 (dimer). We describe the Ca(2+)/calmodulin (CaM) mediated dimerization of AtDEG15. Dimerization is mediated by the CaM-like protein AtCML3 as shown by yeast two and three hybrid analyses. The binding of AtCML3 occurs within the first 25 N-terminal amino acids of AtDEG15, a domain containing a predicted CaM-binding motif. Biochemical analysis of AtDEG15 deletion constructs in planta support the requirement of the CaM-binding domain for PTS2 processing. Phylogenetic analyses indicate that the CaM-binding site is conserved in peroxisomal processing proteases of higher plants (dicots, monocots) but not present in orthologs of animals or cellular slime molds. Despite normal PTS2 processing activity, an atcml3 mutant exhibited reduced 2,4-DB sensitivity, a phenotype previously reported for the atdeg15 mutant, indicating similarly impaired peroxisome metabolism. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11103-013-0112-6) contains supplementary material, which is available to authorized users

Ion homeostasis in the Chloroplast

peer reviewedThe chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis

Spectroscopic properties of azobenzene-based pH indicator dyes: A quantum chemical and experimental study

The UV visible absorption spectra of six new optical sensors based on acidochromic azobenzenes have been measured and assigned with the help of quantum chemical calculations. The investigated compounds are able to monitor the pH in the range from pH 3-10. Using the hybrid density functional PBEO and including solvent effects with a polarized continuum model, the agreement between the experimental and theoretical UV/vis spectra of the dyes in their neutral and anionic forms is very good. The spectroscopic pi pi* states, responsible for the optical properties of the sensors, are described within an accuracy of 0.1 eV. Similar accuracy is demonstrated in the ne states. The pi pi* states can be assigned as a charge transfer from the aromatic pi orbital localized in the azo-phenol moiety to the antibonding pi* of the azo group. Under basic conditions, the spectrum is bathochromically shifted and more intense than in acid media. Upon substitution in the phenyl moiety, red- or blue-shifts of the UV visible bands are observed depending on whether the substituent is electron-donor or -withdrawing, respectively. These effects are stronger at high pH values and can be rationalized in terms of the stabilization and/or destabilization of the involved frontier orbitals