SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers

S′adenosyl-l-methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g−1 fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1–2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO)

FYVE-Dependent Endosomal Targeting of an Arrestin-Related Protein in Amoeba

International audienceBACKGROUND: Visual and β-arrestins are scaffolding proteins involved in the regulation of receptor-dependent intracellular signaling and their trafficking. The arrestin superfamilly includes several arrestin domain-containing proteins and the structurally related protein Vps26. In Dictyostelium discoideum, the arrestin-domain containing proteins form a family of six members, namely AdcA to -F. In contrast to canonical arrestins, Dictyostelium Adc proteins show a more complex architecture, as they possess, in addition to the arrestin core, other domains, such as C2, FYVE, LIM, MIT and SAM, which potentially mediate selective interactions with either lipids or proteins. METHODOLOGY AND PRINCIPAL FINDINGS: A detailed analysis of AdcA has been performed. AdcA extends on both sides of the arrestin core, in particular by a FYVE domain which mediates selective interactions with PI(3)P, as disclosed by intrinsic fluorescence measurements and lipid overlay assays. Localization studies showed an enrichment of tagged- and endogenous AdcA on the rim of early macropinosomes and phagosomes. This vesicular distribution relies on a functional FYVE domain. Our data also show that the arrestin core binds the ADP-ribosylation factor ArfA, the unique amoebal Arf member, in its GDP-bound conformation. SIGNIFICANCE: This work describes one of the 6 arrestin domain-containing proteins of Dictyostelium, a novel and atypical member of the arrestin clan. It provides the basis for a better understanding of arrestin-related protein involvement in trafficking processes and for further studies on the expanding roles of arrestins in eukaryotes

Mycobacterium marinum antagonistically induces an autophagic response while repressing the autophagic flux in a TORC1- and ESX-1-dependent manner.

Autophagy is a eukaryotic catabolic process also participating in cell-autonomous defence. Infected host cells generate double-membrane autophagosomes that mature in autolysosomes to engulf, kill and digest cytoplasmic pathogens. However, several bacteria subvert autophagy and benefit from its machinery and functions. Monitoring infection stages by genetics, pharmacology and microscopy, we demonstrate that the ESX-1 secretion system of Mycobacterium marinum, a close relative to M. tuberculosis, upregulates the transcription of autophagy genes, and stimulates autophagosome formation and recruitment to the mycobacteria-containing vacuole (MCV) in the host model organism Dictyostelium. Antagonistically, ESX-1 is also essential to block the autophagic flux and deplete the MCV of proteolytic activity. Activators of the TORC1 complex localize to the MCV in an ESX-1-dependent manner, suggesting an important role in the manipulation of autophagy by mycobacteria. Our findings suggest that the infection by M. marinum activates an autophagic response that is simultaneously repressed and exploited by the bacterium to support its survival inside the MCV

New insights in the relation between climate and slope failures at high-elevation sites

Climate change is now unequivocal; however, the type and extent of terrestrial impacts are still widely debated. Among these, the effects on slope stability are receiving a growing attention in recent years, both as terrestrial indicators of climate change and implications for hazard assessment. High-elevation areas are particularly suitable for these studies, because of the presence of the cryosphere, which is particularly sensitive to climate. In this paper, we analyze 358 slope failures which occurred in the Italian Alps in the period 2000–2016, at an elevation above 1500 m a.s.l. We use a statistical-based method to detect climate anomalies associated with the occurrence of slope failures, with the aim to catch an eventual climate signal in the preparation and/or triggering of the considered case studies. We first analyze the probability values assumed by 25 climate variables on the occasion of a slope-failure occurrence. We then perform a dimensionality reduction procedure and come out with a set of four most significant and representative climate variables, in particular heavy precipitation and short-term high temperature. Our study highlights that slope failures occur in association with one or more climate anomalies in almost 92% of our case studies. One or more temperature anomalies are detected in association with most case studies, in combination or not with precipitation (47% and 38%, respectively). Summer events prevail, and an increasing role of positive temperature anomalies from spring to winter, and with elevation and failure size, emerges. While not providing a final evidence of the role of climate warming on slope instability increase at high elevation in recent years, the results of our study strengthen this hypothesis, calling for more extensive and in-depth studies on the subject

In vitro selection of fluoroquinolone resistance in Brucella melitensis

International audienceMoxifloxacin-resistant mutants of 16M [moxifloxacin minimum inhibitory concentration (MIC)=1mg/L] were selected in order to characterise fluoroquinolone resistance mechanisms in this species. Eight independent mutants were obtained, with moxifloxacin MICs of 16–32mg/L. The mutants displayed variable cross-resistance levels to other fluoroquinolone compounds, but no increased resistance to aminoglycosides, tetracycline, rifampicin, macrolides or co-trimoxazole. Sequencing of type II topoisomerase-encoding genes (, , and ), which are natural targets for fluoroquinolones, revealed a mutation leading to the amino acid substitution Ala83Val ( numbering system) in five mutants with a moxifloxacin MIC of 32mg/L, whereas no mutation was found in the remaining three mutants with an MIC of 16mg/L. Phenylalanine-arginine-β-naphthylamide dihydrochloride, an efflux pump inhibitor, reduced moxifloxacin MICs by a factor of two to eight in all resistant mutants. In , fluoroquinolone resistance may arise from mutation and efflux pump overexpression mechanisms

Induced polarization as a tool to characterize shallow landslides

International audienceThe development of shallow landslides is strongly connected to the changes in the water content of soils on hillslopes, their clay content and permeability distribution, which, in turn, are playing an important role regarding their hydro-mechanical properties. A non-intrusive geophysical method able to map these properties would be very helpful. The most common geoelectrical method, DC (Direct Current) resistivity, cannot be used as a stand-alone technique for this purpose since it depends on two contributions (bulk and surface conductivities), which depend on the water content and the cation exchange capacity (CEC) of the material. Induced polarization is a geophysical method that can be now used to complement DC resistivity in providing key material properties that can be used to diagnose potential risks for failure. We first recall the basic principles behind the induced polarization method from laboratory to field scales and key findings in the underlying petrophysics needed to jointly interpret electrical conductivity and normalized chargeability tomograms. Then, we apply these relationships to a field survey carried out over a shallow landslide at Claix (Isère, France), close to Grenoble. A 3D induced polarization survey was carried out and interpreted in terms of the clay content, water content, and permeability distributions. We demonstrate that the landslide is associated with a channel of high water content corresponding with the presence of travertine, a flow-path, and a permeability barrier downslope corresponding to the presence of plastic clays. This study demonstrates that induced polarization can be used to characterize the impacted volume and therefore might have been useful to map the area before the landslide to assess the possible risk of failure. This methodology could play a key role in mitigation planning