Intraspecific niche models for the invasive ambrosia beetle Xylosandrus crassiusculus suggest contrasted responses to climate change.

Xylosandrus crassiusculus is an invasive ambrosia beetle comprising two differentiated genetic lineages, named cluster 1 and cluster 2. These lineages invaded different parts of the world at different periods of time. We tested whether they exhibited different climatic niches using Schoener's D and Hellinger's I indices and modeled their current potential geographical ranges using the Maxent algorithm. The resulting models were projected according to future and recent past climate datasets for Europe and the Mediterranean region. The future projections were performed for the periods 2041-2070 and 2071-2100 using 3 SSPs and 5 GCMs. The genetic lineages exhibited different climate niches. Parts of Europe, the Americas, Sub-Saharan Africa, Asia, and Oceania were evaluated as suitable for cluster 1. Parts of Europe, South America, Central and South Africa, Asia, and Oceania were considered as suitable for cluster 2. Models projection under future climate scenarios indicated a decrease in climate suitability in Southern Europe and an increase in North Eastern Europe in 2071-2100. Most of Southern and Western Europe was evaluated as already suitable for both clusters in the early twentieth century. Our results show that large climatically suitable regions still remain uncolonized and that climate change will affect the geographical distribution of climatically suitable areas. Climate conditions in Europe were favorable in the twentieth century, suggesting that the recent colonization of Europe is rather due to an increase in propagule pressure via international trade than to recent environmental changes.

Climate change impact on the potential geographical distribution of two invading Xylosandrus ambrosia beetles.

Xylosandrus compactus and X. crassiusculus are two polyphagous ambrosia beetles originating from Asia and invasive in circumtropical regions worldwide. Both species were recently reported in Italy and further invaded several other European countries in the following years. We used the MaxEnt algorithm to estimate the suitable areas worldwide for both species under the current climate. We also made future projections for years 2050 and 2070 using 11 different General Circulation Models, for 4 Representative Concentration Pathways (2.6, 4.5, 6.0 and 8.5). Our analyses showed that X. compactus has not been reported in all potentially suitable areas yet. Its current distribution in Europe is localised, whereas our results predicted that most of the periphery of the Mediterranean Sea and most of the Atlantic coast of France could be suitable. Outside Europe, our results also predicted Central America, all islands in Southeast Asia and some Oceanian coasts as suitable. Even though our results when modelling its potential distribution under future climates were more variable, the models predicted an increase in suitability poleward and more uncertainty in the circumtropical regions. For X. crassiusculus, the same method only yielded poor results, and the models thus could not be used for predictions. We discuss here these results and propose advice about risk prevention and invasion management of both species.

Natural flavonoids inhibit the plasma membrane Ca2+-ATPase.

Research on flavonoids from plant sources has recently sparked increasing interest because of their beneficial health properties. Different studies have shown that flavonoids change the intracellular Ca2+ homeostasis linked to alterations in the function of mitochondria, Ca2+ channels and Ca2+ pumps. These findings hint at plasma membrane Ca2+-ATPase (PMCA) involvement, as it transports Ca2+ actively to the extracellular medium coupled to ATP hydrolysis, thus maintaining ion cellular homeostasis. The present study aims to investigate the effect of several natural flavonoids on PMCA both in isolated protein systems and in living cells, and to establish the relationship between flavonoid structure and inhibitory activity on PMCA. Our results show that natural flavonoids inhibited purified and membranous PMCA with different effectiveness: quercetin and gossypin were the most potent and their inhibition mechanisms seem to be different, as quercetin does not prevent ATP binding whereas gossypin does. Moreover, PMCA activity was inhibited in human embryonic kidney cells which transiently overexpress PMCA, suggesting that the effects observed on isolated systems could occur in a complex structure like a living cell. In conclusion, this work reveals a novel molecular mechanism through which flavonoids inhibit PMCA, which leads to Ca2+ homeostasis and signaling alterations in the cell.

A dataset on the inventory of coniferous urban trees in the city of Orléans (France).

The dataset supplied in this article provides the spatial location and the species composition of urban trees belonging to three coniferous genera (Pinus, Cedrus and Pseudotsuga) inventoried in 5 districts of the city of Orléans (France). A total of 9321 trees were georeferenced. The most abundant species was the black pine Pinus nigra for which a total of 2420 trees were observed. Other common species were the scots pine P. sylvestris, the Douglas-fir Pseudotsuga menziesii and different species of the genus Cedrus. The data supplied in this article are related to "A citywide survey of the pine processionary moth Thaumetopoea pityocampa spatial distribution in Orléans (France)" by J.-P. Rossi, V. Imbault, T. Lamant, J. Rousselet,) [3].

Incipient allochronic speciation in the pine processionary moth (Thaumetopoea pityocampa, Lepidoptera, Notodontidae).

A plausible case of allochronic differentiation, where barrier to gene flow is primarily attributable to a phenological shift, was recently discovered in Portugal for the pine processionary moth Thaumetopoea pityocampa. Previous results suggested that the observed 'summer population' (SP) originated from the sympatric winter population (WP). Our objectives were to finely analyse these patterns and test their stability in time, through field monitoring and genetic analyses of larvae and adults across different years. Reproductive activity never overlapped between SP and WP. Microsatellites showed a clear differentiation of the SP, consistent with a strong reduction in gene flow owing to the phenological shift. Assignment tests suggested that some individuals shift from the SP to the WP phenology, causing some hybridization. We discuss these patterns and their maintenance over time. This could be a first stage of allochronic speciation, and SP should be considered as a distinct phenological race.

Geostatistical genetic analysis for inferring the dispersal pattern of a partially clonal species: example of the chestnut blight fungus.

Spatial genetic analyses can be used to infer dispersal processes in natural populations. For partially clonal species with alternating sexual and asexual reproduction, the repetition of genotypes must be taken into account in analyses. The methods currently employed to evaluate the relevance of the spatial scale used for the estimation of gene flow are not suitable for these species. We investigated recently developed methods for taking into account repeated genotypes and for determining whether the sampling scale is large enough to capture all the spatial genetic structure existing within a population. We applied these methods to a fungal plant pathogen species, Cryphonectria parasitica, which has caused the death of many American and European chestnut trees since its introduction from Asia at the beginning of the 20th century. These methods were found to be useful for unravelling the effects of clonality and historical gene flow on the spatial genetic structure, and indicated that dispersal processes have probably occurred over a larger spatial scale than previously assumed.

Expression and cellular distribution pattern of plasma membrane calcium pump isoforms in rat pancreatic islets.

This work is aimed at identifying the presence and cellular distribution pattern of plasma membrane calcium pump (PMCA) isoforms in normal rat pancreatic islet. Microsomal fractions of isolated islets and exocrine tissue were analyzed to detect different PMCA isoforms. The cellular distribution pattern of these PMCAs in the islets was also studied in fixed pancreas sections incubated with antibodies against PMCAs and insulin. Antibody 5F10, which reacts with all PMCA variants, showed multiple bands in the blots in the 127-134 kDa region, indicating the presence of several isoforms. Microsomes also reacted positively with specific antibodies for individual PMCA isoforms, generating a band of the expected size. Antibody 5F10 immunocytochemically labeled the plasma cell membrane of both b- and non-b-cells, but predominantly the former. All islet cells were also labeled with antibodies against isoforms 1 and 4, while the antibody reacting with isoform 3 labeled exclusively b-cells. A few b- and non-b-cells were positively labeled with the antibody reacting with PMCA b variant. Negative results were obtained with the antibody against isoform 2. Further studies, together with previous reports on the modulatory effect of insulin secretagogues and blockers upon PMCA activity, may provide evidence of the importance of this particular PMCA expression for islet function under normal and pathological conditions.

Synthesis and human leukocyte elastase inhibitory evaluation of phosphate triesters and acyl phosphates of penam sulfides and sulfones.

The synthesis of 6,6-dibromo-3alpha-(diphenylphosphate)oxymethyl-2,2-dimethyl penam sulfone (3a), 6alpha-chloro-3alpha-(diphenylphosphate)oxymethyl-2,2-dimethyl penam sulfone (3b), benzyl 6alpha-(diphenyl-phosphate)oxypenicillanate sulfone (4) and 6,6-dibromo-3alpha-(methylphosphate)carbonyl-2,2-dimethylpenam sulfone (12) are reported. When tested as inhibitors of human leukocyte elastase, the compound 4 proved to be the most active.

Quantitation of plasma membrane calcium pump phosphorylated intermediates by electrophoresis.

P-ATPases are characterized by the formation of acid-stable phosphorylated intermediates (EP) during their reaction cycle. We have developed a microscale method to determine EP that involves the phosphorylation of the enzyme using [gamma-(32)P]ATP and precipitation with TCA; separation of the sample by SDS-PAGE, and measurement of the enzyme protein and (32)P-labeled EP by digital analysis of both the stained gel and its autoradiogram, respectively. The principal advantages of this method over typical procedures (filtration and centrifugation) are the low amount of enzyme required and the substantial decrease in the blank values and data scattering produced by unspecific phosphorylation and nonquantitative recovering of the enzyme. Application of this new method to a purified preparation of the plasma membrane calcium ATPase (PMCA) results in overcoming the difficulties of measuring EP at high ATP concentrations. A biphasic behavior of the substrate curve for EP was observed when the study was extended to ATP levels within the physiological range. Since, in principle, the method does not require the use of highly purified preparations, it could be helpful for the study of phosphorylated intermediates especially under conditions in which small amounts of protein are available, e.g., mutated variants of P-ATPases.

Oligomerization of the plasma membrane calcium pump involves two regions with different thermal stability.

Ca(2+) pump dimerization was studied by using a combined approach of thermal denaturation and fluorescence resonance energy transfer. The measurement of calcium pump ability to dimerize after the unfolding of individual functional domains of the enzyme demonstrated the existence of two different regions involved in the self-association process. One of these regions is highly susceptible to thermal unfolding and was identified as the calmodulin (CaM)-binding domain. The other region whose thermal stability is higher than those of the catalytic and CaM-binding domains could be related with the previously found C28W-binding regions.

Export and folding of signal-sequenceless Bacillus licheniformis beta-lactamase in Escherichia coli.

Two genetically engineered variants of the Bacillus licheniformis beta-lactamase gene were expressed in Escherichia coli. One variant coded for the exo-small mature enzyme without the signal peptide. The other coded for the exo-large mature enzyme preceded by 10, mostly polar, residues from an incomplete heterologous signal. As observed following the extraction by a lysozyme-EDTA treatment, the signal-less variant was exported to the periplasm with nearly 20% efficiency, whereas the variant with the N-terminal extension was translocated to a lesser degree; interestingly, nearly all of the former and half of the latter were extracted by osmotic shock, which may be of importance for our understanding of cellular compartments. The fact that a signal-less protein is translocated with substantial yields raises questions about the essential role of signal peptides for protein export. As folding and export are related processes, we investigated the folding in vitro of the two variants. No differences were found between them. In the absence of denaturant, they are completely folded, fully active and have a large DeltaG of unfolding. Under partially denaturing conditions they populate several partially folded states. The absence of significant amounts of a non-native state under native conditions makes a thermodynamic partitioning between folding and export less likely. In addition, kinetic measurements indicated that these B. licheniformis lactamases fold much faster than E. coli beta-lactamase. This behavior suggests that they are exported by a kinetically controlled process, mediated by one or more still unidentified interactions that slow folding and allow a folding intermediate to enter the export pathway.

Thermal stability of the plasma membrane calcium pump. Quantitative analysis of its dependence on lipid-protein interactions.

Thermal stability of plasma membrane Ca(2+) pump was systematically studied in three micellar systems of different composition, and related with the interactions amphiphile-protein measured by fluorescence resonance energy transfer. Thermal denaturation was characterized as an irreversible process that is well described by a first order kinetic with an activation energy of 222 +/- 12 kJ/mol in the range 33-45 degrees C. Upon increasing the mole fraction of phospholipid in the mixed micelles where the Ca(2+) pump was reconstituted, the kinetic coefficient for the inactivation process diminished until it reached a constant value, different for each phospholipid species. We propose a model in which thermal stability of the pump depends on the composition of the amphiphile monolayer directly in contact with the transmembrane protein surface. Application of this model shows that the maximal pump stability is attained when 80% of this surface is covered by phospholipids. This analysis provides an indirect measure of the relative affinity phospholipid/detergent for the hydrophobic transmembrane surface of the protein (K(LD)) showing that those phospholipids with higher affinity provide greater stability to the Ca(2+) pump. We developed a method for directly measure K(LD) by using fluorescence resonance energy transfer from the membrane protein tryptophan residues to a pyrene-labeled phospholipid. K(LD) values obtained by this procedure agree with those obtained from the model, providing a strong evidence to support its validity.

Molecular characterization of the glycated plasma membrane calcium pump.

We have previously demonstrated (Diabetes 39:707-711, 1990) that in vitro glycation of the red cell Ca(2+) pump diminishes the Ca(2+)-ATPase activity of the enzyme up to 50%. Such effect is due to the reaction of glucose with lysine residues of the Ca(2+) pump (Biochem. J. 293:369-375, 1993). The aim of this work was to determine whether the effect of glucose is due to a full inactivation of a fraction of the total population of Ca(2+) pump, or to a partial inactivation of all the molecules. Glycation decreased the V(max) for the ATPase activity leaving unaffected the apparent affinities for Ca(2+), calmodulin or ATP. The apparent turnover was identical in both, the glycated and the native enzyme. Glycation decreased the V(max) for the ATP-dependent but not for the calmodulin-activated phosphatase activities. Concomitantly with the inhibition, up to 6.5% of the lysine residues were randomly glycated. The probabilistic analysis of the relation between the enzyme activity and the fraction of nonmodified residues indicates that only one Lys residue is responsible for the inhibition. We suggest that glucose decreases the Ca(2+)-ATPase activity by reacting with one essential Lys residue probably located in the vicinity of the catalytic site, which results in the full inactivation of the enzyme. Thus, Ca(2+)-ATPase activity measured in erythrocyte membranes or purified enzyme preparations preincubated with glucose depends on the remaining enzyme molecules in which the essential Lys residue stays unglycated.

Identification of Bordetella pertussis virulence-associated outer membrane proteins.

Bordetella pertussis virulence-associated 30-, 32-, 90- and 95-kDa outer membrane proteins were purified and their N-terminal amino acid sequences were determined. The 30- and 32-kDa outer membrane proteins showed identity to the C-terminal region of the precursors of the serum resistance protein (BrkA) and the tracheal colonization factor, respectively. We confirmed the cleavage site of these precursors after N731 for BrkA and after N393 for tracheal colonization factor. Associated with the 32-kDa outer membrane protein, we found a new group of 36-kDa virulence-associated peptides. The 95-kDa outer membrane protein showed identity to Vag8. The 90-kDa outer membrane protein did not show homology with the described proteins. We report the N-termini sequence of Vir-90, a novel potential virulence factor.

Temperature-induced conformational transition of intestinal fatty acid binding protein enhancing ligand binding: a functional, spectroscopic, and molecular modeling study.

Intestinal fatty acid binding protein (IFABP) undergoes a reversible thermal transition between 35 and 50 degreesC, as revealed by circular dichroism spectroscopy in the near-UV region. For the apoprotein, the molar ellipticity measured at 254 nm (possibly implicating the environment around F17 and/or F55) decreases significantly in this temperature range, while in the holoprotein (bound to oleic acid), this phenomenon is not observed. Concomitantly, an increase in the activity of binding to [14C]oleic acid occurs. Nevertheless, other spectroscopic evidence indicates that the beta-barrel structure, the major motif of this protein, is highly stable up to 70 degreesC. No changes associated with conformation were detected for both structures by fourth-derivative analysis of the UV absorption spectra, circular dichroism in the far-UV region, and intrinsic fluorescence measurements. Further structural information arises from experiments in which binding to the anionic fluorescent probes 1-anilinonaphthalene-8-sulfonic acid (ANS) and its dimer bisANS was examined. The fluorescence intensity of bound ANS diminishes monotonically, whereas that of bisANS increases slightly in the temperature range of 35-50 degreesC. Given the different size of these probes, model building suggests that ANS would be able to sense regions located deeply inside the cavity, while bisANS could also reach the vicinity of the small helical domain of this protein. In light of these results, we believe that this subtle conformational transition of IFABP, which positively influences the binding activity, would involve fluctuations at the peripheral "entry portal" region for the ligand. This interpretation is compatible with the discrete disorder observed in this place in apo-IFABP, as evidenced by NMR spectroscopy [Hodsdon, M. E., and Cistola, D. P. (1997) Biochemistry 36, 1450-1460].

Chemical modification reveals involvement of different sites for nucleotide analogues in the phosphatase activity of the red cell calcium pump.

The calcium pump of plasma membranes catalyzes the hydrolysis of ATP and phosphoric esters like p-nitrophenyl phosphate (pNPP). The latter activity requires the presence of ATP and/or calmodulin, and Ca2+ [22, 25]. We have studied the effects of nucleotide-analogues and chemical modifications of nucleotide binding sites on Ca2+-pNPPase activity. Treatment with fluorescein isothiocyanate (FITC), abolished Ca2+-ATPase and ATP-dependent pNPPase, but affected only 45% of the calmodulin-dependent pNPPase activity. The nucleotide analogue eosin-Y had an inhibitory effect on calmodulin-dependent pNPPase (Kieosin-Y = 2 microM). FITC treatment increased Kieosin-Y 15 times. Acetylation of lysine residues with N-hydroxysuccinimidyl acetate inactivates Ca2+-ATPase by modifying the catalytic site, and impairs stimulation by modulators by modifying residues outside this site [9]. Acetylation suppressed the ATP-dependent pNPPase with biphasic kinetics. ATP or pNPP during acetylation cancels the fast component of inactivation. Acetylation inhibited only partially the calmodulin-dependent pNPPase, but neither ATP nor pNPP prevented this inactivation. From these results we conclude: (i) ATP-dependent pNPPase depends on binding of ATP to the catalytic site; (ii) the catalytic site plays no role in calmodulin-dependent pNPPase. The decreased affinity for eosin-Y of the FITC-modified enzyme, suggests that the sites for these two molecules are closely related but not overlapped. Acetimidation of the pump inhibited totally the calmodulin-dependent pNPPase, but only partially the ATP-pNPPase. Since calmodulin binds to E1, the E1 conformation or the E2 if E1 transition would be involved during calmodulin-dependent pNPPase activity.

Effect of 2-hydroxyoestradiol on insulin secretion in normal rat pancreatic islets.

The possible action of 2-hydroxyoestradiol (2-OHE2) on glucose-induced insulin secretion was evaluated in pancreatic islets isolated from normal rats by collagenase digestion and incubated in KRB buffer. Insulin output in response to either 3.3 or 16.6 mM glucose was measured by radioimmunoassay in the absence or presence of different concentrations of 2-OHE2, norepinephrine (NE), or oestradiol. Islets were also incubated with 2-OHE2, NE, or oestradiol plus a fixed concentration (1 microM) of the alpha 2-adrenergic-receptor blocking agent yohimbine. The results showed that 2-OHE2, oestradiol and NE within a range of 0.1 to 20 microM inhibited glucose-induced insulin secretion in a dose-dependent manner: Ki (microM): 0.04 +/- 0.0001, 0.04 +/- 0.0002, and 0.01 +/- 9.1 E-6 respectively. This suppression was significantly reversed by yohimbine. Contrary to NE and 2-OHE2, oestradiol at lower concentrations (increasing within a range of 0.001 to 0.05 microM) in incubation medium in the same experimental conditions had a significant stimulatory effect on insulin secretion. Thus, it would appear that catecholoestrogens suppress islet insulin release via alpha 2-adrenergic receptors, which suggests that oestrogens may exert a dual modulatory effect on insulin secretion by enhancing release via direct interaction with the cytosolic-oestrogen receptor and inhibiting release after their local hydroxylation and the interaction of their new catechol moiety with alpha 2-adrenergic receptors. Our results suggest that these compounds may play a complementary role to CAs as negative modulators, and they also provide a broader scope for understanding the effect of oestrogens and/or their metabolites in the control of endocrine functions other than those related to reproduction.

The pitch of short-duration fundamental frequency glissandos.

Pitch perception for short-duration fundamental frequency (F0) glissandos was studied. In the first part, new measurements using the method of adjustment are reported. Stimuli were F0 glissandos centered at 220 Hz. The parameters under study were: F0 glissando extents (0, 0.8, 1.5, 3, 6, and 12 semitones, i.e., 0, 10.17, 18.74, 38.17, 76.63, and 155.56 Hz), F0 glissando durations (50, 100, 200, and 300 ms), F0 glissando directions (rising or falling), and the extremity of F0 glissandos matched (beginning or end). In the second part, the main results are discussed: (1) perception seems to correspond to an average of the frequencies present in the vicinity of the extremity matched; (2) the higher extremities of the glissando seem more important; (3) adjustments at the end are closer to the extremities than adjustments at the beginning. In the third part, numerical models accounting for the experimental data are proposed: a time-average model and a weighted time-average model. Optimal parameters for these models are derived. The weighted time-average model achieves a 94% accurate prediction rate for the experimental data. The numerical model is successful in predicting the pitch of short-duration F0 glissandos.

The membrane topology of the amino-terminal domain of the red cell calcium pump.

A systematic study of the membrane-associated regions in the plasma membrane Ca2+ pump of erythrocytes has been performed by hydrophobic photolabeling. Purified Ca2+ pump was labeled with 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)-diazirine ([125I]TID), a generic photoactivatable hydrophobic probe. These results were compared with the enzyme labeled with a strictly membrane-bound probe, [3H]bis-phosphatidylethanolamine (trifluoromethyl) phenyldiazirine. A significant light-dependent labeling of an M(r) 135,000-140,000 peptide, corresponding to the full Ca2+ pump, was observed with both probes. After proteolysis of the pump labeled with each probe and isolation of fragments by SDS-PAGE, a common pattern of labeled peptides was observed. Similarly, labeling of the Ca2+ pump with [125I]TID, either in isolated red blood cell membranes or after the enzyme was purified, yields a similar pattern of labeled peptides. Taken together, these results validate the use of either probe to study the lipid interface of the membrane-embedded region of this protein, and sustain the notion that the conformation of the pump is maintained throughout the procedures of solubilization, affinity purification, and reconstitution into proteoliposomes. In this work, we put special emphasis on a detailed analysis of the N-terminal domain of the Ca2+ pump. A labeled peptide of M(r) 40,000 belonging to this region was purified and further digested with V8 protease. The specific incorporation of [125I]TID to proteolytic fragments pertaining to the amino-terminal region indicates the existence of two transmembrane stretches in this domain. A theoretical analysis based on the amino acid sequence 1-322 predicts two segments with high probability of membrane insertion, in agreement with the experimental data. Each segment shows a periodicity pattern of hydrophobicity and variability compatible with alpha-helical structure. These results strongly suggest the existence of a transmembrane helical hairpin motif near the N-terminus of the Ca2+ pump.