BVOC Emissions From a Subarctic Ecosystem,as Controlled by Insect Herbivore Pressure and Temperature

Ecosystems - The biogenic volatile organic compounds, BVOCs have a central role in ecosystem–atmosphere interactions. High-latitude ecosystems are facing increasing temperatures and insect...     

Interactive effect of elevated temperature and O<Subscript>3</Subscript> on antioxidant capacity and gas exchange in <Emphasis Type="Italic">Betula pendula</Emphasis> saplings

We studied the effects of slightly elevated temperature (T), O₃ concentration (O₃) and their combination (T + O₃) on the antioxidant defense, gas exchange and total leaf area of Betula pendula saplings in field conditions. During the second year of the experiment, T enhanced the total leaf area, net photosynthesis (P _n) and maximum capacity of carboxylation, redox state of ascorbate and total antioxidant capacity in the apoplast. O₃ did not affect the total leaf area, but P _n was slightly and g _s significantly reduced. The saplings responded to elevated O₃ level by closing the stomata and by developing leaves with a lower leaf area per mass, rather than by accumulating ascorbate in the apoplast. The effects of T and O₃ on total leaf area and P _n were counteractive. Elevated O₃ reduced the saplings’ ability to utilize the warmer growth environment by increasing the stomatal limitation for photosynthesis and by reducing the redox state of ascorbate in the apoplast in the combination treatment as compared to T alone.     

N-Glycosylation Regulates Fibroblast Growth Factor Receptor/EGL-15 Activity in Caenorhabditis elegans in Vivo

The regulation of cell function by fibroblast growth factors (FGFs) classically occurs through a dual receptor system of a tyrosine kinase receptor (FGFR) and a heparan sulfate proteoglycan co-receptor. Mutations in some consensus N-glycosylation sites in human FGFR result in skeletal disorders and craniosynostosis syndromes, and biophysical studies in vitro suggest that N-glycosylation of FGFR alters ligand and heparan sulfate binding properties. The evolutionarily conserved FGFR signaling system of Caenorhabditis elegans has been used to assess the role of N-glycosylation in the regulation of FGFR signaling in vivo. The C. elegans FGF receptor, EGL-15, is N-glycosylated in vivo, and genetic substitution of specific consensus N-glycosylation sites leads to defects in the maintenance of fluid homeostasis and differentiation of sex muscles, both of which are phenotypes previously associated with hyperactive EGL-15 signaling. These phenotypes are suppressed by hypoactive mutations in EGL-15 downstream signaling components or activating mutations in the phosphatidylinositol 3-kinase pathway, respectively. The results show that N-glycans negatively regulate FGFR activity in vivo supporting the notion that mutation of N-glycosylation sites in human FGFR may lead to inappropriate activation of the receptor.     

Erwinia carotovora subsp. carotovora and Erwinia-derived elicitors HrpN and PehA trigger distinct but interacting defense responses and cell death in Arabidopsis

We have used an hrp-positive strain of the soft rot pathogen Erwinia carotovora subsp. carotovora to elucidate plant responses to this bacterial necrotroph. Purified virulence determinants, harpin (HrpN) and polygalacturonase (PehA), were used as tools to facilitate this analysis. We show that HrpN elicits lesion formation in Arabidopsis and tobacco and triggers systemic resistance in Arabidopsis. Establishment of resistance is accompanied by the expression of salicylic acid (SA)-dependent, but also jasmonate/ethylene (JA/ET)-dependent, marker genes PR1 and PDF1.2, respectively, suggesting that both SA-dependent and JA/ET-dependent defense pathways are activated. Use of pathway-specific mutants and transgenic NahG plants show that both pathways are required for the induction of resistance. Arabidopsis plants treated simultaneously with both elictors PehA, known to trigger only JA/ET-dependent defense signaling, and HrpN react with accelerated and enhanced induction of the marker genes PR1 and PDF1.2 both locally and systemically. This mutual amplification of defense gene expression involves both SA-dependent and JA/ET-dependent defense signaling. The two elicitors produced by E. carotovora subsp. carotovora also cooperate in triggering increased production of superoxide and lesion formation.     

Liquid chromatography method for plant and mammalian lignans in human urine

Recently new mammalian lignan precursors were identified but no analysis methods are available for assay of those compounds in human urine. Previously published methods were developed for GC-MS about only two plant lignans were included. Consequently, a method for HPLC equipped with a coulometric electrode array detector was developed to measure plant and mammalian lignans in human urine. The plant lignans, secoisolariciresinol (Seco), matairesinol (Mat), lariciresinol (Lar), pinoresinol (Pin), syringaresinol (Syr) and isolariciresinol (IsoL) were included into the new method together with two mammalian lignans, enterolactone (Enl) and enterodiol (End). Validation of the method demonstrated that it could be applied to normal urine containing low amounts of plant lignans and moderate amounts of mammalian lignans, but the method was also applicable for samples from study subjects in supplementation studies, i.e. sample with very high concentrations of mammalian lignans. The method was found to be a useful tool for studies on plant lignan intake and the activity of micro flora in the metabolism of plant lignans.     

Effects of ultraviolet-B radiation on growth, mycorrhizas and mineral nutrition of silver birch (Betula pendula Roth) seedlings grown in low-nutrient conditions

The effects of increased ultraviolet‐B (UV‐B) radiation on the growth, mycorrhizas and mineral nutrition of silver birch (Betula pendula Roth) seedlings were studied in greenhouse conditions. Seedlings—planted in a birch‐forest top soil and sand substrate—were grown without additional nutrient supply. Ultraviolet treatment started immediately after the seedlings emerged and the daily integrated biologically effective UV‐B irradiance on the UV‐B‐treated plants was equivalent to a 25% depletion of stratospheric ozone under clear sky conditions. Visible symptoms of UV‐B damage or nutrient deficiency were not observed throughout the experiment. Seedling height and dry weight (DW) (measured after 58 days and 76 days of treatment) were not affected by increased UV‐B. However, a significant shift in DW allocation toward roots resulted in a lower shoot/root ratio and leaf area ratio in UV‐B‐treated plants compared to control plants. At the first harvest (after 58 days of treatment), the percentage of various mycorrhizal morphotypes and the number of short roots per unit of root length or weight were not affected by increased UV‐B despite significantly increased DW allocation toward roots. Subtle reduction in the allocation of nitrogen (N) to leaves and increased allocation of phosphorus (P) to roots may suggest cumulative effects that could affect the plant performance over the long‐term.     

Phylogenetic evidence for the distinction of Saaremaa and Dobrava hantaviruses

Background

Simian virus 40 (SV40) enters cells via an atypical caveolae-mediated endocytic pathway, which delivers the virus to a new intermediary compartment, the caveosome. The virus then is believed to go directly from the caveosome to the endoplasmic reticulum. Cholera toxin likewise enters via caveolae and traffics to caveosomes. But, in contrast to SV40, cholera toxin is transported from caveosomes to the endoplasmic reticulum via the Golgi. For that reason, and because the caveosome and Golgi may have some common markers, we revisited the issue of whether SV40 might access the endoplasmic reticulum via the Golgi.

Results

We confirmed our earlier finding that SV40 co localizes with the Golgi marker β-COP. However, we show that the virus does not co localize with the more discriminating Golgi markers, golgin 97 and BODIPY-ceramide.

Conclusion

The caveolae-mediated SV40 entry pathway does not intersect the Golgi. SV40 is seen to co localize with β-COP because that protein is a marker for caveosomes as well as the Golgi. Moreover, these results are consistent with the likelihood that the caveosome is a sorting organelle. In addition, there are at least two distinct but related routes by which a ligand might traffic from the caveosome to the ER; one route involving transport through the Golgi, and another pathway that does not involve the Golgi.     

The role of microtubules in the regulation of proteoglycan synthesis in chondrocytes under hydrostatic pressure

Chondrocytes of the articular cartilage sense mechanical factors associated with joint loading, such as hydrostatic pressure, and maintain the homeostasis of the extracellular matrix by regulating the metabolism of proteoglycans (PGs) and collagens. Intermittent hydrostatic pressure stimulates, while continuous high hydrostatic pressure inhibits, the biosynthesis of PGs. High continuous hydrostatic pressure also changes the structure of cytoskeleton and Golgi complex in cultured chondrocytes. Using microtubule (MT)-affecting drugs nocodazole and taxol as tools we examined whether MTs are involved in the regulation of PG synthesis in pressurized primary chondrocyte monolayer cultures. Disruption of the microtubular array by nocodazole inhibited [(35)S]sulfate incorporation by 39-48%, while MT stabilization by taxol caused maximally a 17% inhibition. Continuous hydrostatic pressure further decreased the synthesis by 34-42% in nocodazole-treated cultures. This suggests that high pressure exerts its inhibitory effect through mechanisms independent of MTs. On the other hand, nocodazole and taxol both prevented the stimulation of PG synthesis by cyclic 0. 5 Hz, 5 MPa hydrostatic pressure. The drugs did not affect the structural and functional properties of the PGs, and none of the treatments significantly affected cell viability, as indicated by the high level of PG synthesis 24-48 h after the release of drugs and/or high hydrostatic pressure. Our data on two-dimensional chondrocyte cultures indicate that inhibition of PG synthesis by continuous high hydrostatic pressure does not interfere with the MT-dependent vesicle traffic, while the stimulation of synthesis by cyclic pressure does not occur if the dynamic nature of MTs is disturbed by nocodazole. Similar phenomena may operate in cartilage matrix embedded chondrocytes.