Temperature stress can alter the photosynthetic efficiency and secondary metabolite concentrations in St. John's wort.

Temperature stress is known to cause many physiological, biochemical and molecular changes in plant metabolism and possibly alter the secondary metabolite production in plants. The hypothesis of the current study was that temperature stress can increase the secondary metabolite concentrations in St. John's wort. Plants were grown under controlled environments with artificial light using cool white fluorescent lamps and CO2 enrichment and 70-day-old plants were subjected for 15 days to different temperature treatments of 15, 20, 25, 30 and 35 degrees C before harvested. Major aim of the study was to increase the major secondary metabolites in St. John's wort by applying temperature stress and to evaluate the physiological status of the plant especially the photosynthetic efficiency and peroxidase activity of the leaf tissues exposed to different temperatures under precisely controlled environmental factors. Results revealed that relatively high (35 degrees C) or low (15 degrees C) temperatures reduced the photosynthetic efficiency of the leaves of St. John's wort plants and resulted in low CO2 assimilation. Net photosynthetic rates and the maximal quantum efficiency of PSII photochemistry of the dark adopted leaves (phi(p)max) decreased significantly in the leaves of plants grown under 35 or 15 degrees C temperature treatments. High temperature (35 degrees C) treatment increased the leaf total peroxidase activity and also increased the hypericin, pseudohypericin and hyperforin concentrations in the shoot tissues. These results provide the first indication that temperature is an important environmental factor to optimize the secondary metabolite production in St. John's wort and controlled environment technology can allow the precise application of such specific stresses.     

Extracellular laccase production and its optimization from Arthrospira maxima catalyzed decolorization of synthetic dyes

In the present study laccase production potential of a photosynthetic, non nitrogen fixing cyanobacteria Arthrospira maxima (SAE-25780) was investigated for their probable use in synthetic dye decolorization which poses environmental pollution problem in aquatic bodies. A. maxima (SAE-25780) showed a constitutive production of laccase which increased up to 80% in the presence of inducer guaiacol. The optimal condition for laccase was 30 °C, 10 mM sucrose as a carbon source, 10 mM sodium nitrate as a nitrogen source, and 2 mM copper as metal activator. The partially purified laccase showed 84% and 49% decolorization potential for the two anthroquinonic dyes-Reactive Blue 4 and Remazol Brilliant Blue R, respectively (RBBR) within 96 h without any mediator. Therefore the laccase extracted from A. maxima (SAE-25780) can be used efficiently in bioremediation of synthetic dyes from paper, pulp and textile industries.     

Floral constraint resulting from intersexual mimicry in a gynodioecious fig tree

Fig trees (Ficus: Moraceae) are pollinated by female fig wasps (Agaonidae) whose larvae develop inside galled flowers of unusual inflorescences (figs). Most fig trees also support communities of non‐pollinating fig wasps. Figs of different species display great size variation and contain tens to tens of thousands of flowers. Around one‐half the species of fig trees have the gynodioecious breeding system, where female trees have figs that produce seeds and male trees have figs that support development of pollinators. Mutual mimicry between receptive male and female figs ensures that pollinators enter female figs, even though the insects will die without reproducing, but the need to give no sex‐specific cues to the pollinators may constrain differences in size between receptive male and female figs. We compared relationships between inflorescence size and some measures of reproductive success in male and female figs of Ficus montana grown under controlled conditions in the presence of the pollinator Kradibia tentacularis and its main parasitoid Sycoscapter sp. indesc. Female figs that contained more flowers produced more seeds, but male figs did not increase the production of female pollinator K. tentacularis fig wasps in proportion of the flower number. Although more flowers were galled by the pollinators in male figs containing more female flowers, the high larval mortality caused by parasitism and nutritional limitation prevented the increase in the production of adult female offspring. Selection may favor the increase in flower numbers within figs in female plants of F. montana, but contrarily constrain this attribute in male plants.     

Conserved Amphipathic Helices Mediate Lipid Droplet Targeting of Perilipins 1–3

Perilipins (PLINs) play a key role in energy storage by orchestrating the activity of lipases on the surface of lipid droplets. Failure of this activity results in severe metabolic disease in humans. Unlike all other lipid droplet-associated proteins, PLINs localize almost exclusively to the phospholipid monolayer surrounding the droplet. To understand how they sense and associate with the unique topology of the droplet surface, we studied the localization of human PLINs in Saccharomyces cerevisiae, demonstrating that the targeting mechanism is highly conserved and that 11-mer repeat regions are sufficient for droplet targeting. Mutations designed to disrupt folding of this region into amphipathic helices (AHs) significantly decreased lipid droplet targeting in vivo and in vitro. Finally, we demonstrated a substantial increase in the helicity of this region in the presence of detergent micelles, which was prevented by an AH-disrupting missense mutation. We conclude that highly conserved 11-mer repeat regions of PLINs target lipid droplets by folding into AHs on the droplet surface, thus enabling PLINs to regulate the interface between the hydrophobic lipid core and its surrounding hydrophilic environment.     

Interactions between pollinator and non‐pollinator fig wasps: correlations between their numbers can be misleading

Ficus and their species–specific pollinator fig wasps represent an obligate plant–insect mutualism, but figs also support a community of non‐pollinating fig wasps (NPFWs) that consist of phytophages and parasitoids or inquilines. We studied interactions between Kradibia tentacularis, the pollinator of a dioecious fig tree species Ficus montana, and an undescribed NPFW Sycoscapter sp. Members of Sycoscapter sp. oviposited 2–4 weeks after pollinator oviposition, when host larvae were present in the figs. No negative correlation was found between the numbers of the two wasp species emerging from figs in a semi‐natural population. However, in experiments where the numbers of pollinator foundresses entering a fig were controlled, Sycoscapter sp. significantly reduced the numbers of pollinator offspring. Consequently, it can be concluded that Sycoscapter sp. is a parasitoid of K. tentacularis (which may also feed on plant tissue). Sycoscapter females concentrate their oviposition in figs that contain more potential hosts, rendering invalid conclusions based on simple correlations of host and natural enemy numbers.     

De-differentiation of primary human hepatocytes depends on the composition of specialized liver basement membrane

Despite the understanding of the importance of mitogen-activated protein (MAP) kinase activation in the stimulation of growth, little is known about the role of MAP kinase regulation during contact inhibited growth control. To investigate the role of the MAP kinase extracellular signal-regulated kinase (ERK) during the transition to a contact inhibited state, cultures of normal fibroblasts (BJ) were grown to different stages of confluency. The levels of MAP kinase phosphatase (MKP) expression and the amount of active ERK and MAP ERK kinase (MEK) in these cultures were assessed through western blot analysis and were compared to fibrosarcoma cell cultures (HT-1080), which lack contact inhibition. In normal fibroblasts, the amounts of active MEK and ERK decline at contact inhibition, concurrently with a rise in MKP-1, MKP-2, and MKP-3 protein levels. In contrast, fibrosarcoma cells appear to lack density-dependent regulation of the ERK pathway. Additionally, altering the redox environment of fibrosarcoma cells to a less reducing state, as seen during contact inhibition, results in increased MKP-1 expression. Taken together, these results suggest that the altered redox environment upon contact inhibition may contribute to the regulation of ERK inactivation by MKPs.     

In vitro antituberculosis activities of the constituents isolated from Haloxylon salicornicum

In vitro antituberculosis activities of fractions and pure compounds (1–20) including seven triterpenes, two alkaloids, two cycloheximide derivatives, two coumarins six sterol derivatives and a long chain alcohol, respectively, isolated from Haloxylon salicornicum were determined against Mycobecterium tuberculosis H37Rv. Actively growing cultures were tested by rapid colorimetric method while the stationary phase cultures were tested by drug exposure methods for bactericidal activity. The MIC values were found to be 50 μg/ml for compounds 15, 19 and 20 where as rest of the compounds invariably showed MIC value of 100 μg/ml against the logarithmic phase culture. These were compare to Isoniazid as a control drug. The compounds exhibited no activity against the stationary phase culture of M. tuberculosis H37Rv up to 200 μg/ml. Further studies are required to investigate the in vivo efficacies and activities of the compounds in combination with antimicrobials that are already being used for TB therapy.