Tree formations in relation with soil and grasses in a dry savanna in Mali, West Africa

The relationship between trees, grass and soil in a dry savanna in Mali was investigated, to identify variables that are most relevant to assess vegetation units. A 65 ha plateau was inventoried using a systematic square grid sampling pattern. Thirteen soil or topography variables, and tree and grass characteristics were measured at each sampling point. Multivariate analysis was used to separately analyse soil, tree and grass data, and to characterize tree–grass and tree–soil relationships. Four units of soils, four units of tree formations, and four units of grass formations were identified. There was a correspondence between these groups, indicative of four vegetation units: thicket, bare land, shrub savanna and tree savanna. Soil depth and soil texture were the soil variables that best related to tree vegetation. A negative correlation was found between tree basal area and grass dry biomass. Finally, vegetation units, as identified from tree species composition, had contrasted diameter structures and densities.     

Conformational disturbance induced by AzPro/Pro substitution in peptides

Consequences inherent to the substitution ofaza-proline (AzPro) for proline in the octapeptideTTSAPTTS, representative of the tandem repeat motifpresent in the peptide backbone of MUC5AC mucin, wereanalysed in terms of conformational perturbation andO-glycosylation aptitude. In DMSO solution, weobserved the same tendency previously noted inAzPro-tripeptide models, i.e. AzPro prevents-turn formation in which it would occupy thei+1 position, and therefore behaves quite oppositeto Pro, whereas both AzPro and Pro can support a-turn in the i+2 position with a cisdisposition of the preceding tertiary amide function.The former structural modifications do not preventO-glycosylation to take place at the same specificsite, but it occurs at a reduced rate.     

Microbial and plant-derived compounds both contribute to persistent soil organic carbon in temperate soils

Our study tests the emerging paradigm that biochemical recalcitrance does not affect substantially long-term (50 years) SOC persistence. We analyzed the molecular composition of SOC in archived soils originating from four European long-term bare fallow experiments (Askov, Rothamsted, Versailles and Ultuna). The soils had been collected after various periods (up to 53 years) under bare fallow. With increasing duration of bare fallow without new organic inputs, the relative abundance of cutin- and suberin-derived compounds declined substantially, and the abundance of lignin-derived compounds was close to zero. Conversely, the relative abundance of plant-derived long-chain alkanes remained almost constant or increased during the bare fallow period. The relative abundance of N-containing compounds, considered to be abundant in SOC derived from microbial activity, increased consistently illustrating that microbial turnover of SOC continues even when plant inputs are stopped. The persistence of the different families of plant-derived compounds differed markedly over the scale of half a century, which may be ascribed to their contrasting chemical characteristics and recalcitrance, or to differences in their interactions with the soil mineral matrix, and likely some combination since chemical composition drives the degree of mineral association. Using soil from this unique set of long-term bare fallow experiments, we provide direct evidence that multi-decadal scale persistent SOC is enriched in microbe-derived compounds but also includes a substantial fraction of plant-derived compounds.     

G3BP1, G3BP2 and CAPRIN1 Are Required for Translation of Interferon Stimulated mRNAs and Are Targeted by a Dengue Virus Non-coding RNA

Viral RNA-host protein interactions are critical for replication of flaviviruses, a genus of positive-strand RNA viruses comprising major vector-borne human pathogens including dengue viruses (DENV). We examined three conserved host RNA-binding proteins (RBPs) G3BP1, G3BP2 and CAPRIN1 in dengue virus (DENV-2) infection and found them to be novel regulators of the interferon (IFN) response against DENV-2. The three RBPs were required for the accumulation of the protein products of several interferon stimulated genes (ISGs), and for efficient translation of PKR and IFITM2 mRNAs. This identifies G3BP1, G3BP2 and CAPRIN1 as novel regulators of the antiviral state. Their antiviral activity was antagonized by the abundant DENV-2 non-coding subgenomic flaviviral RNA (sfRNA), which bound to G3BP1, G3BP2 and CAPRIN1, inhibited their activity and lead to profound inhibition of ISG mRNA translation. This work describes a new and unexpected level of regulation for interferon stimulated gene expression and presents the first mechanism of action for an sfRNA as a molecular sponge of anti-viral effectors in human cells.     

Adaptive behaviour of fishers to external perturbations: simulation of the Tasmanian rock lobster fishery

The rock lobster, Jasus edwardsii, lies on a global “hotspot” for climate change in the southeastern Australian state of Tasmania. The short-term effects of climate change are predicted to lead to an increasing exploitable biomass in the south and declining biomass in the north of the state. The future of the fishery is highly uncertain due to climate change, but also due to insecurities linked to the market conditions. The market for Tasmanian rock lobster is driven by the demand of a single market, China, which absorbs 75 % of the catch. This study examines how fishers can adapt to external perturbations that affect the social and economic viability of the fleet and the ecological dynamics of the stock. Three fleet dynamic models of increasing complexity are used to investigate the effects of climate change and lobster price changes on the fishery. There could be local depletion leading to negative short-term profit for the fleet if it is static and the proportion of the total catch taken in each region of the fishery does not respond to climate-induced-changes. Better outcomes would occur if the fleet adapts dynamically to environmental conditions, and fishing effort follows stock abundance, which would counter-act the short-term effects of climate change. Only a model with explicit representation of economic drivers can fully capture the local economic and social impacts of large scale global perturbations.     

Formation of N-branched oligonucleotides as by-products in solid-phase oligonucleotide synthesis

During the synthesis of oligonucleotides by the standard phosphoramidite method using 2'-deoxycytidine- derivatized solid support, a side reaction was observed that gave rise to the formation of high molecular weight N-branched oligomers having two identical chains linked to the 3'-terminal 2'-deoxycytidine.Postsynthesis treatment with neat triethylamine trihydrofluoride selectively cleaved the phosphoramidate linkage and converted the N-branched oligomers back to the expected oligonucleotides.     

Synthesis and secondary structure in membranes of the Bcl-2 anti-apoptotic domain BH4.

Solid phase synthesis of BH4, the 26 amino-acid domain (6RTGYDNREIVMKYIHYKLSQRGYEWD31) of the anti-apoptotic Bcl-2 protein has been accomplished using Fmoc chemistry. The use of peculiar cleavage conditions provided high yields after purification such that tens to hundreds of mg could be obtained. A 15N-labelled version of the peptide could also be synthesized for NMR studies in membranes. The peptide purity was not lower than 98% as controlled by UV and MALDI-TOF mass spectrometry. The secondary structure was determined in water, trifluoroethanol (TFE) and in lipid membrane using UV circular dichroism. The peptide shows dominant beta-sheeted structures in water that convert progressively into alpha-helical features upon addition of TFE or membrane. The amphipathic character of the helix suggests that the peptide might have a structure akin to those of antimicrobial peptides upon interaction with membranes.