The Cell Wall as a Barrier Against Water Loss and Plant Pathogens

The ability to survive a range of stresses is crucial to the survival of plants. Structural modifications in the cell wall through pectin cross linkages may be key to mitigating damage caused by stress. Pectin reduces cell wall permeability and increases rigidity through calcium ion crosslinks to carboxylate ions in galacturonic acid residues in homogalacturonan, and boron crosslinks to apiosyl residues in rhamnogalacturonan II side chains. The objective of this research was to understand the influence of calcium and boron in vitro, and how changes in viscosity and rigidity may translate to resistance to dehydration and fungal pathogens in Allium spp. and Arabidopsis pectin methylesterase/boron mutant genotypes. Allium spp. served as an ideal model to study dehydration stress as the cells are large and a single layer of epidermal cells can be easily separated. Arabidopsis was useful given the availability of mutant genotypes. CaCl2 and H3BO3 were both found to significantly (p0.05) and Colletotrichum higginsianum infection (p<0.05). Because of the mechanism of infection, the rapid rate of Colletotrichum higginsianum infection in bor1 is indicative of a weak cell wall. While the response to stress is highly complex, collectively this thesis indicates calcium, boron, pectin and the cell wall in general may play important but relatively under researched roles in plant resistance to both abiotic and biotic stress

Komposisi Jenis dan Kelimpahan Fitoplankton Perairan Laut Riau

This research was conducted in April 2013 and was located at Riau marine waters. Samples were analyzed in the Biology Laboratory of Marine Science Department of Fisheries and Marine Science Faculty of Riau University. The aim of this study was to observe the phytoplankton communities. This research used survey method. The study found 31 species of phytoplankton, these were 19 species from Bacillariophyceae, 9 species from Dinophyceae, 2 species from Chlorophyceae and 1 species from Cyanophyceae. Phytoplankton was dominated by group of Bacillariophyceae (Diatoms) 61%. The other groups comprising of Dinophyceae 29%, Chlorophyceae (7%), and Cyanophyceae 3%. Phytoplankton abundance varied from 87-593 ind/L, the higest value in station 9 Zone III and the lowest value in station 11 zone III. Whereas the highest value of zone abundance was zone II 443 ind/L and the lowest was zone I 253 ind/L. Phytoplankton community was dominated by the group of diatoms, such as Nitzschia sigma, Thallasiothrix longissima, and Thallasiothrix delicatula

Tissue-specific regulation of Igf2r/Airn imprinting during gastrulation

Background Appropriate epigenetic regulation of gene expression during lineage allocation and tissue differentiation is required for normal development. One example is genomic imprinting, which is defined as parent-of-origin mono-allelic gene expression. Imprinting is established largely due to epigenetic differences arriving in the zygote from sperm and egg haploid genomes. In the mouse, there are approximately 150 known imprinted genes, many of which occur in imprinted gene clusters that are regulated together. One imprinted cluster includes the maternally expressed Igf2r, Slc22a2, and Slc22a3 genes and the paternally expressed long non-coding RNA (lncRNA) Airn. Although it is known that Igf2r and Airn are reciprocally imprinted, the timing of imprinted expression and accompanying epigenetic changes have not been well characterized in vivo. Results Here we show lineage- and temporal-specific regulation of DNA methylation and histone modifications at the Igf2r/Airn locus correlating with differential establishment of imprinted expression during gastrulation. Our results show that Igf2r is expressed from both alleles in the E6.5 epiblast. After gastrulation commences, the locus becomes imprinted in the embryonic lineage with the lncRNA Airn expressed from the paternal allele and Igf2r restricted to maternal allele expression. We document differentially enriched allele-specific histone modifications in extraembryonic and embryonic tissues. We also document for the first time allele-specific spreading of DNA methylation during gastrulation concurrent with establishment of imprinted expression of Igf2r. Importantly, we show that imprinted expression does not change in the extraembryonic lineage even though maternal DMR2 methylation spreading does occur, suggesting distinct mechanisms at play in embryonic and extraembryonic lineages. Conclusions These results indicate that similar to preimplantation, gastrulation represents a window of dynamic lineage-specific epigenetic regulation in vivo

Personenmarken erfolgreich managen : ein markenpersönlichkeitsbasierter Steuerungsansatz

Personen, wie beispielsweise Sportler, Politiker, Künstler oder Manager, die ihre Leistungen und zunehmend auch sich selb st vermarkten, können als Marken verstanden werden. Ähnlich wie Gütermarken stehen auch Personenmarken immer häufiger vor der Herausforderung, durch eine erfolgreiche Differenzierung im Verdrängungswettbewerb zu bestehen. Trotz ihres enormen wirtschaftlichen Potenzials existiert für Personenmarken bislang kein systematischer Ansatz zur Differenzierung gegenüber der Konkurrenz und somit auch keine Grundlage für ihre effektive Vermarktung. Im vorliegenden Beitrag wird daher zunächst dargestellt, dass das Konzept der Marke auf Personen übertragen und der im Gütermarketing erfolgreich eingesetzte Differenzierungsansatz der Markenpersönlichkeit auch im Kontext von Personenmarken angewendet werden kann. In einem weiteren Schritt werden die im Rahmen einer empirischen Studie ermittelten Einflussfaktoren der Markenpersönlichkeit von Personenmarken vorgestellt und ihre Einsatzmöglichkeiten für ein effektives strategisches Management von Personenmarken beschrieben

Effect of different monomer precursors with identical functionality on the properties of the polymer network

Thermo-mechanical properties of polymer networks depend on functionality of the monomer precursors -- an association that is frequently exploited in materials science. We use molecular simulations to generate spatial networks from chemically different monomers with identical functionality and show that such networks have several universal graph-theoretical properties as well as near universal Young's modulus. The vitrification temperature is shown to be universal only up to a certain density of the network, as measured by the bond conversion. The latter observation is explained by the fact that monomer's tendency to coil enhances formation of topological holes, which, when accumulated in the network, amount to a percolating cell complex restricting network's mobility. This higher-order percolation occurs late after gelation and is shown to coincide with the onset of brittleness, as indicated by a sudden increase in the glass transition temperature. This phenomenon may signify a new type of phase transition in polymer materials