Origin and dispersion pathways of guava in the Galapagos Islands inferred through genetics and historical records

Guava (Psidium guajava) is an aggressive invasive plant in the Galapagos Islands. Determining its provenance and genetic diversity could explain its adaptability and spread, and how this relates to past human activities. With this purpose, we analyzed 11 SSR markers in guava individuals from Isabela, Santa Cruz, San Cristobal, and Floreana islands in the Galapagos, as well as from mainland Ecuador. The mainland guava population appeared genetically differentiated from the Galapagos populations, with higher genetic diversity levels found in the former. We consistently found that the Central Highlands region of mainland Ecuador is one of the most likely origins of the Galapagos populations. Moreover, the guavas from Isabela and Floreana show a potential genetic input from southern mainland Ecuador, while the population from San Cristobal would be linked to the coastal mainland regions. Interestingly, the proposed origins for the Galapagos guava coincide with the first human settlings of the archipelago. Through approximate Bayesian computation, we propose a model where San Cristobal was the first island to be colonized by guava from the mainland, and then, it would have spread to Floreana and finally to Santa Cruz; Isabela would have been seeded from Floreana. An independent trajectory could also have contributed to the invasion of Floreana and Isabela. The pathway shown in our model agrees with the human colonization history of the different islands in the Galapagos. Our model, in conjunction with the clustering patterns of the individuals (based on genetic distances), suggests that guava introduction history in the Galapagos archipelago was driven by either a single event or a series of introduction events in rapid succession. We thus show that genetic analyses supported by historical sources can be used to track the arrival and spread of invasive species in novel habitats and the potential role of human activities in such processes.     

Structural rearrangement of model membranes by the peptide antibiotic NK-2

We have developed a novel α-helical peptide antibiotic termed NK-2. It efficiently kills bacteria, but not human cells, by membrane destruction. This selectivity could be attributed to the different membrane lipid compositions of the target cells. To understand the mechanisms of selectivity and membrane destruction, we investigated the influence of NK-2 on the supramolecular aggregate structure, the phase transition behavior, the acyl chain fluidity, and the surface charges of phospholipids representative for the bacterial and the human cell cytoplasmic membranes. The cationic NK-2 binds to anionic phosphatidylglycerol liposomes, causing a thinning of the membrane and an increase in the phase transition temperature. However, this interaction is not solely of electrostatic but also of hydrophobic nature, indicated by an overcompensation of the Zeta potential. Whereas NK-2 has no effect on phosphatidylcholine liposomes, it enhances the fluidity of phosphatidylethanolamine acyl chains and lowers the phase transition enthalpy of the gel to liquid cristalline transition. The most dramatic effect, however, was observed for the lamellar/inverted hexagonal transition of phosphatidylethanolamine which was reduced by more than 10 °C. Thus, NK-2 promotes a negative membrane curvature which can lead to the collapse of the phosphatidylethanolamine-rich bacterial cytoplasmic membrane.     

A proteomic approach identified growth hormone-dependent nutrition markers in children with idiopathic short stature

Background  

The broad range in growth observed in short prepubertal children receiving the same growth hormone (GH) dose is due to individual variation in GH responsiveness. This study used a pharmaco-proteomic approach in order to identify novel biomarkers that discriminate between short non-GH-deficient (GHD) children who show a good or poor growth response to GH treatment.     

Influence of the germline sequence on the thermodynamic stability and fibrillogenicity of human lambda 6 light chains

Light chain-associated amyloidosis is a fatal disease characterized by the aggregation and pathologic deposition of monoclonal light chain-related fragments as amyloid fibrils in organs or tissues throughout the body. Notably, it has been observed that proteins encoded by the lambda variable light chain (V(L)) gene segment 6a are invariably associated with amyloid deposition; however, the contribution of the gene to this phenomenon has not been established. In this regard, we have determined the thermodynamic stability and kinetics of in vitro fibrillogenesis of a recombinant (r) V(L) protein, designated 6aJL2, which contains the predicted sequences encoded by the 6a and JL2 germline genes. Additionally, we studied a 6a mutant (6aJL2-Arg25Gly), that is present in approximately 25% of all amyloid-associated lambda6 light chains. Remarkably, the wild-type 6aJL2 protein was more stable than were all known amyloidogenic kappa and lambda light chains for which stability parameters are available; more importantly, it was even more so (and less fibrillogenic) than the only clinically proven nonamyloidogenic lambda6 protein, Jto. Conversely, the mutated 6aJL2-R25G molecule was considerably less stable and more fibrillogenic than was the native 6aJL2. Our data indicate that the propensity of lambda6 light chains to form amyloid can not be attributed to thermodynamic instability of the germline-encoded Vlambda6 domain, but rather, is dependent on sequence alterations that render such proteins amyloidogenic.     

Detection and structural investigation of metabolites of stanozolol in human urine by liquid chromatography tandem mass spectrometry

The applicability of LC–MS/MS in precursor ion scan mode for the detection of urinary stanozolol metabolites has been studied. The product ion at m/z 81 has been selected as specific for stanozolol metabolites without a modification in A- or N-rings and the product ions at m/z 97 and 145 for the metabolites hydroxylated in the N-ring and 4-hydroxy-stanozolol metabolites, respectively. Under these conditions, the parent drug and up to 15 metabolites were found in a positive doping test sample. The study of a sample from a chimeric uPA-SCID mouse collected after the administration of stanozolol revealed the presence of 4 additional metabolites. The information obtained from the product ion spectra was used to develop a SRM method for the detection of 19 compounds. This SRM method was applied to several doping positive samples. All the metabolites were detected in both the uPA-SCID mouse sample and positive human samples and were not detected in none of the blank samples tested; confirming the metabolic nature of all the detected compounds. In addition, the application of the SRM method to a single human excretion study revealed that one of the metabolites (4ξ,16ξ-dihydroxy-stanozolol) could be detected in negative ionization mode for a longer period than those commonly used in the screening for stanozolol misuse (3′-hydroxy-stanozolol, 16β-hydroxy-stanozolol and 4β-hydroxy-stanozolol) in doping analysis. The application of the developed approach to several positive doping samples confirmed the usefulness of this metabolite for the screening of stanozolol misuse. Finally, a tentative structure for each detected metabolite has been proposed based on the product ion spectra measured with accurate masses using UPLC–QTOF MS.     

Proteins related to lipoprotein profile were identified using a pharmaco-proteomic approach as markers for growth response to growth hormone (GH) treatment in short prepubertal children

Background  

The broad range in growth observed in response to growth hormone (GH) treatment is mainly caused by individual variations in both GH secretion and GH sensitivity. Individual GH responsiveness can be estimated using evidence-based models that predict the response to GH treatment; however, these models can be improved. High-throughput proteomics techniques can be used to identify proteins that may potentially be used as variables in such models in order to improve their predictive ability. Previously we have reported that proteomic analyses can identify biomarkers that discriminate between short prepubertal children with idiopathic short stature (ISS) who show good or poor growth in response to GH treatment. In this study we used a pharmaco-proteomic approach to identify novel factors that correlate with the growth response to GH treatment in prepubertal children who are short due to GH deficiency or ISS. The study included 128 short prepubertal children receiving GH treatment, of whom 39 were GH-deficient and 89 had ISS. Serum protein expression profiles at study start and after 1 year of GH treatment were analyzed using SELDI-TOF. Cross-validated regression and random permutation analyses were performed to identify significant correlations between protein expression patterns and the 2-year growth response to GH treatment.     

An interesting diagnosis for a presacral mass: case report

A presacral mass can present a diagnostic dilemma for the surgical oncologist. Differential diagnoses include congenital causes such as teratoma or chordoma, neurological causes such as neurilemoma or neurofibroma or other malignancies such as lymphoma or sarcoma. Diagnosis usually requires imaging such as CT and MRI and tissue biopsy. We present an unusual cause of a presacral mass being extramedullary haematopoiesis, found incidentally in a 71 year old female. Extramedullary haematopoiesis is defined as the production of myeloid and erythroid elements outside of the bone-marrow. This diagnosis is extremely rare in the presacral area especially in a patient with no haematological abnormalities. A review of the literature is presented.     

Presence of yeasts in floral nectar is consistent with the hypothesis of microbial-mediated signaling in plant-pollinator interactions

Olfactory floral signals are significant factors in plant-pollinator mutualisms. Recently, unusual fermentation odors have been described in the nectar and flowers of some species. Since yeasts are common inhabitants of many angiosperms nectars, this raises the possibility that nectar yeasts may act as causal agents of fermentation odors in flowers and, therefore, as possible intermediate agents in plant signaling to pollinators. A recent field study has reported that nectar yeasts were quite frequent in floral nectar across three different regions in Europe and America, where they reached high densities (up to 10⁵ cells/mm³). Yeast incidence in floral nectar differed widely across plant host species in all sampling sites. A detailed study currently in progress on one of the species surveyed in that study (Helleborus foetidus, Ranunculaceae) has detected that, in addition to interespecific differences in yeast incidence, there is also a strong component of variance in yeast abundance that takes place at the subindividual level (among flowers of the same plant, among nectaries of the same flower). If yeast metabolism is eventually proved to contribute significantly to floral scent, then multilevel patchiness in the distribution of nectar yeasts (among species, among individuals within species, and among flowers and nectaries of the same individual) might contribute to concomitant multilevel variation in plant signaling and, eventually, also in pollination success, pollen flow and plant fitness.Key words: nectar, yeast, scent, plant-animal interaction, plant signalingPollinators forage on a wide range of flowers that differ in morphology, color, scent and quality and quantity of reward. The majority of these floral features are important visual and olfactory cues that are directly related to plant-pollinators signaling and the pollination process.^1–12 Recently, the intriguing possibility has been raised that microbial communities (especially nectarivorous yeasts) inhabiting flowers could explain better than, or in addition to, plant physiology itself, certain floral features that participate in plant-pollinators signaling, like yeasty nectar or floral scent.^13,14 However, some of these suggestions are based on circumstantial or indirect evidence indicative of the presence of microbes in flowers. For example, fermentation odors have been described in a number of Angiosperms,^14–16 in which different compounds found in nectar were not shared with any other floral parts.¹³ In addition, yeasty odors (ketones and shortchain alcohols) have only been observed in mature flowers that were already visited by pollinators and thus potentially contaminated with microbes, in contrast, for example, to the sesquiterpenes isolated in immature flowers that are also common in the foliage of many plants.¹⁴ Yeasty odors were found in species whose flowers are long-lived, produce large amounts of nectar, and are visited by flies and beetles, which are known to act as yeast vectors to flowers.^17–19 In spite of these plausible suggestions, studies indicating a potential role of microbes in the origin of floral scents generally have not looked directly for their presence or abundance in floral nectar, which clearly would provide critical empirical evidence in support of the hypothesis of microbial-mediated signaling in plant-pollinator interactions.That yeasts are common inhabitants of floral nectars was well known to microbiologists more than a century ago^20,21 and has been recently corroborated by Herrera et al.²² This study was conducted at three widely separated areas, which differed greatly in ecological features and biogeographical affinities: two study sites were located in the Southern Iberian Peninsula, about 350 km apart, and one in Yucatán Peninsula, eastern Mexico. Floral nectar samples from 40, 63 and 37 species, belonging to 21, 23 and 21 families, were examined microscopically for yeast cells at these three areas. Yeasts occurred very frequently in floral nectar at all areas, as revealed by the high proportion of nectar samples that contained them (31.8%, 42.3% and 54.4%; samples from all species at each site combined). In addition to being quite frequent in nectar samples, yeast cells often reached extraordinarily high densities in floral nectar at the three areas, which reached roughly 4 × 10⁵ cells/mm³. When plant species, rather than individual nectar samples, were considered as the units for analyses, Herrera et al.²² found wide variation among species in both the frequency of occurrence and the density of yeasts in nectar samples. A significant fraction of such variation was found to be correlated with differences in pollinator composition, a link between pollination ecology and floral nectar microbiology that has remained unexplored until now. Similar results showing high densities and frequency of occurrence of yeasts in nectar, and interespecific differences in these magnitudes related to variation in pollinator composition, have been also reported by de Vega et al.²³ for 40 South African plant species, which further supports the generality of the phenomenon. In addition to interespecific differences in the prevalence of nectar yeasts, the data examined by Herrera et al.²² and de Vega et al.²³ revealed also considerable intraespecific variability (i.e., among individuals plants of the same species), although this aspect of results was not explicitly considered in their studies.A study currently in progress has documented patterns of intraespecific variability in yeast occurrence in the nectaries of Helleborus foetidus (Ranunculaceae), a winter-flowering, bumble bee-pollinated perennial herb whose long-lived flowers last for roughly two weeks. Frequency of occurrence and cell density of yeasts in nectar were studied at six populations of this species from Sierra de Cazorla (SE Spain). Helleborus foetidus flowers have five separated horn-shaped nectaries hidden at the corolla base, each of which produces up to 5 µl of nectar. This enabled us to study patterns of yeast occurrence also at the within-flower level. At each population, total variance in yeast cell density on a per-nectary basis was partitioned into components due to differences between individual plants, flowers within plants and nectaries within flowers. We found extreme differences concerning the abundance and frequency of yeasts in H. foetidus nectar, the magnitude of intraespecific variation being similar or even greater than variation found in interespecific comparisons in the same study area (Pozo MI, et al. unpublished results). Our data suggest that temporal and spatial factors may explain differences regarding yeast abundance in H. foetidus nectar, and possibly other species as well. The largest component of intraespecific variance in yeast abundance occurred at the subindividual level, and was mainly accounted for by the variance between nectaries in the same flower (Fig. 1). This intraespecific variation in nectarivorous yeast incidence can have some important implications related to plant-pollinators interactions and, more specifically, to plant signaling, as outlined below.Open in a separate windowFigure 1Hierarchical dissection of variance in yeast abundance in single-nectary nectar samples of Helleborus foetidus. (A) Temporal patterns. Collection dates and plant, flower within plant and nectary within flower as hierarchical levels of variance analyzed. (B) Spatial patterns. Population, plant within populations and flower within plants as hierarchical levels of variance analyzed.Nectar-inhabiting yeasts modify certain flower characteristics linked to pollinator foraging behavior, such as nectar sugar composition and energetic value, by reducing total sugar concentration and altering the relative proportions of constituent sugars (sucrose, glucose and fructose) and the sucrose:hexose ratio.^23–26 Furthermore, as noted above, yeasts could be also implicated in floral volatiles emission.^13,14 Consequently, yeast incidence (measured both by frequency and abundance of yeast cells in nectar samples) may have been modifying signaling cues which have been postulated to be intrinsic plant species-specific. Although an empirical connection between yeast presence and fermentation nectar odor is needed, the fact that nectarivorous yeast presence would be as variable as described by our studies could imply the same variability for plant species signaling aspects, along with potential consequences for pollinators, since variance was mainly accounted for by variation below individual plant level. For example, in H. foetidus study variance in yeast abundance occurs mainly at the single nectary, which matches with the smallest scale that is perceived by a foraging insect. The fact that nectar is an important floral reward that plays a decisive role in the establishment of plant-pollinator mutualisms, together with the recently confirmed ubiquity of nectarivorous yeasts which could be acting as parasites of such mutualisms, open up new and exciting avenues to explore their effect on pollination success and pollen flow^27–30 and finally on plant fitness.^31–35     

Glial innate immunity generated by non-aggregated alpha-synuclein in mouse: differences between wild-type and Parkinson's disease-linked mutants

Background

Parkinson''s disease (PD) is a progressive neurodegenerative disorder characterized pathologically by the presence in the brain of intracellular protein inclusions highly enriched in aggregated alpha-synuclein (α-Syn). Although it has been established that progression of the disease is accompanied by sustained activation of microglia, the underlying molecules and factors involved in these immune-triggered mechanisms remain largely unexplored. Lately, accumulating evidence has shown the presence of extracellular α-Syn both in its aggregated and monomeric forms in cerebrospinal fluid and blood plasma. However, the effect of extracellular α-Syn on cellular activation and immune mediators, as well as the impact of familial PD-linked α-Syn mutants on this stimulation, are still largely unknown.

Methods and Findings

In this work, we have compared the activation profiles of non-aggregated, extracellular wild-type and PD-linked mutant α-Syn variants on primary glial and microglial cell cultures. After stimulation of cells with α-Syn, we measured the release of Th1- and Th2- type cytokines as well as IP-10/CXCL10, RANTES/CCL5, MCP-1/CCL2 and MIP-1α/CCL3 chemokines. Contrary to what had been observed using cell lines or for the case of aggregated α-Syn, we found strong differences in the immune response generated by wild-type α-Syn and the familial PD mutants (A30P, E46K and A53T).

Conclusions

These findings might contribute to explain the differences in the onset and progression of this highly debilitating disease, which could be of value in the development of rational approaches towards effective control of immune responses that are associated with PD.