Modelling Terrestrial and Marine Foraging Habitats in Breeding Audouin's Gulls Larus audouinii: Timing Matters

Although the breeding ecology of Audouin’s gull has been widely studied, its spatial distribution patterns have received little attention. We assessed the foraging movements of 36 GPS-tracked adult Audouin’s gulls breeding at the Ebro Delta (NW Mediterranean), coinciding with the incubation period (May 2011). This also coincided with a trawling moratorium northwards from the colony. We modelled the distribution of the gulls by combining these tracking data with environmental variables (including fishing activities from Vessel Monitoring System, VMS), using Maxent. The modelling range included both marine and terrestrial areas. Models were produced separately for every 2h time interval across the day, and for 2 fishing activity scenarios (workdays vs. weekends), allowing to assess the spatio-temporal distribution patterns of the gulls and the degree of association with fisheries. During workdays, gull distribution at sea fully matched with fishing activities, both trawling (daylight) and purse-seining (nightime). Gulls tended to avoid the area under trawling moratorium, confirming the high influence of fisheries on the distribution patterns of this species. On weekends, gulls made lesser use of the sea and tended to increase the use of rice fields. Overall, Audouin’s gull activity was more intense during dailight hours, although birds also showed nocturnal activity, on both workdays and weekends. Nocturnal patterns at sea were more disperse during the latter, probably because these gulls are able to capture small pelagic fish at night in natural conditions, but tend to congregate around purse-seiners (which would enhance their foraging efficiency) in workdays. These results provide important insight for the management of this species. This is of particular relevance under the current scenario of European fisheries policies, since new regulations are aimed at eliminating discards, and this would likely influence Audouin’s gull populations.     

Focus on Metabolism: Changes in Whole-Plant Metabolism during the Grain-Filling Stage in Sorghum Grown under Elevated CO2 and Drought

Projections indicate an elevation of the atmospheric CO₂ concentration ([CO₂]) concomitant with an intensification of drought for this century, increasing the challenges to food security. On the one hand, drought is a main environmental factor responsible for decreasing crop productivity and grain quality, especially when occurring during the grain-filling stage. On the other hand, elevated [CO₂] is predicted to mitigate some of the negative effects of drought. Sorghum (Sorghum bicolor) is a C₄ grass that has important economical and nutritional values in many parts of the world. Although the impact of elevated [CO₂] and drought in photosynthesis and growth has been well documented for sorghum, the effects of the combination of these two environmental factors on plant metabolism have yet to be determined. To address this question, sorghum plants (cv BRS 330) were grown and monitored at ambient (400 µmol mol⁻¹) or elevated (800 µmol mol⁻¹) [CO₂] for 120 d and subjected to drought during the grain-filling stage. Leaf photosynthesis, respiration, and stomatal conductance were measured at 90 and 120 d after planting, and plant organs (leaves, culm, roots, prop roots, and grains) were harvested. Finally, biochemical composition and intracellular metabolites were assessed for each organ. As expected, elevated [CO₂] reduced the stomatal conductance, which preserved soil moisture and plant fitness under drought. Interestingly, the whole-plant metabolism was adjusted and protein content in grains was improved by 60% in sorghum grown under elevated [CO₂].Global food demand is projected to increase up to 110% by the middle of this century (Tilman et al., 2011; Alexandratos and Bruinsma, 2012), particularly due to a rise in world population that is likely to plateau at about 9 billion people (Godfray et al., 2010). Additionally, the average concentration of atmospheric CO₂ ([CO₂]) has increased 1.75 µmol mol⁻¹ per year between 1975 and today, reaching 400 µmol mol⁻¹ in April 2015 (NOAA, 2015). According to the A2 emission scenario from the U.S. Environmental Protection Agency, in the absence of explicit climate change policy, atmospheric CO₂ concentrations will reach 800 µmol mol⁻¹ by the end of this century. The increasing atmospheric [CO₂] is resulting in global climate changes, such as reduction in water availability and elevation in temperature. These factors are expected to heavily influence food production in the next years (Godfray and Garnett, 2014; Magrin et al., 2014).Sorghum (Sorghum bicolor) is a C₄ grass, considered a staple food grain for millions of the poorest and most food-insecure people in the semiarid tropics of Africa, Asia, and Central America, serving as an important source of energy, proteins, vitamins, and minerals (Taylor et al., 2006). Moreover, this crop is used for animal feed and as industrial raw material in developed countries such as the United States, which is the main world producer (FAO, 2015). With a fully sequenced genome (Paterson et al., 2009) and over 45,000 accessions representing a large geographic and genetic diversity, sorghum is a good model system in which to study the impact of global climate changes in C₄ grasses.The increase in [CO₂] in the atmosphere, which is the main driver of global climate changes (Meehl et al., 2007), is predicted to boost photosynthesis rates and productivity in a series of C₃ legumes and cereals, mainly due to a decrease in the photorespiration process (Grashoff et al., 1995; Long et al., 2006). On the contrary, due to their capacity to concentrate CO₂ in bundle sheath cells and reduce photorespiration to virtually zero, C₄ plants are unlikely to respond to the elevation of atmospheric [CO₂] (Leakey, 2009). However, even for C₄ plants, elevated [CO₂] can ameliorate the effects caused by drought, maintaining higher photosynthetic rates. This is due to an improvement in the efficiency of water use that is achieved by the reduction in stomatal conductance (Leakey et al., 2004; Markelz et al., 2011).The rate of photosynthesis as well as the redistribution of photoassimilates accumulated in different plant tissues during the day and/or during vegetative growth are crucial to grain development, and later, to its filling (Schnyder, 1993). Due to this relationship, any environmental stress such as drought occurring during the reproductive phase has the potential to result in poor grain filling and losses in yield (Blum et al., 1997). For instance, postanthesis drought can cause up to 30% decrease in yield (Borrell et al., 2000). It is also known that elevated [CO₂], drought, high temperature, and any combinations of these stresses can lead to significant changes in grain composition (Taub et al., 2008; Da Matta et al., 2010; Uprety et al., 2010; Madan et al., 2012), suggesting diverse metabolic alterations and/or adaptations that occur in the plant when it is cultivated in such conditions.Although the impacts of elevated [CO₂] and drought on photosynthesis and the growth of sorghum have been well documented (Conley et al., 2001; Ottman et al., 2001; Wall et al., 2001), no attention has been given to the impact of the combination of these two environmental changes on plant metabolism and composition. Regarding physiology, studies on the growth of sorghum under elevated [CO₂] and drought showed an increase of the net assimilation rate of 23% due to a decrease of 32% in stomatal conductance (Wall et al., 2001). This resulted in sorghum’s ability to use water 17% more efficiently (Conley et al., 2001). An improvement in the final overall biomass under elevated [CO₂] and drought has also been described (Ottman et al., 2001), but without a significant effect in grain yield (Wall et al., 2001).Few studies have been monitoring metabolic pathways in plants under elevated [CO₂] (Li et al., 2008; Aranjuelo et al., 2013) and drought (Silvente et al., 2012; Nam et al., 2015; Wenzel et al., 2015). Furthermore, to our knowledge, there are only two reports in which metabolite profiles or metabolic pathways were investigated under the combination of these two environmental conditions (Sicher and Barnaby, 2012; Zinta et al., 2014). Although it is widely accepted that whole-plant metabolism and composition can impact grain filling and yield, metabolic studies conducted so far have focused on a specific plant organ. For instance, Sicher and Barnaby (2012) analyzed the metabolite profile of leaves from maize (Zea mays) plants that were grown under elevated [CO₂] and drought, but they did not show how those environmental changes could have affected the metabolism of other tissues (e.g. culm and roots) or how they might have influenced the biomass or grain composition.In order to address how the combination of elevated [CO₂] and drought can modify whole-plant metabolism as well as biomass composition in sorghum, this study aimed to (1) evaluate photosynthesis, growth, and yield; (2) underline the differences in biomass composition and primary metabolite profiles among leaves, culm, roots, prop roots, and grains; and (3) determine the effect of elevated [CO₂] and drought on the primary metabolism of each organ.     

Glycans from Fasciola hepatica Modulate the Host Immune Response and TLR-Induced Maturation of Dendritic Cells

Helminths express various carbohydrate-containing glycoconjugates on their surface, and they release glycan-rich excretion/secretion products that can be very important in their life cycles, infection and pathology. Recent evidence suggests that parasite glycoconjugates could play a role in the evasion of the immune response, leading to a modified Th2-polarized immune response that favors parasite survival in the host. Nevertheless, there is limited information about the nature or function of glycans produced by the trematode Fasciola hepatica, the causative agent of fasciolosis. In this paper, we investigate whether glycosylated molecules from F. hepatica participate in the modulation of host immunity. We also focus on dendritic cells, since they are an important target of immune-modulation by helminths, affecting their activity or function. Our results indicate that glycans from F. hepatica promote the production of IL-4 and IL-10, suppressing IFNγ production. During infection, this parasite is able to induce a semi-mature phenotype of DCs expressing low levels of MHCII and secrete IL-10. Furthermore, we show that parasite glycoconjugates mediate the modulation of LPS-induced maturation of DCs since their oxidation restores the capacity of LPS-treated DCs to secrete high levels of the pro-inflammatory cytokines IL-6 and IL-12/23p40 and low levels of the anti-inflammatory cytokine IL-10. Inhibition assays using carbohydrates suggest that the immune-modulation is mediated, at least in part, by the recognition of a mannose specific-CLR that signals by recruiting the phosphatase Php2. The results presented here contribute to the understanding of the role of parasite glycosylated molecules in the modulation of the host immunity and might be useful in the design of vaccines against fasciolosis.     

The Bacterium Endosymbiont of Crithidia deanei Undergoes Coordinated Division with the Host Cell Nucleus

In trypanosomatids, cell division involves morphological changes and requires coordinated replication and segregation of the nucleus, kinetoplast and flagellum. In endosymbiont-containing trypanosomatids, like Crithidia deanei, this process is more complex, as each daughter cell contains only a single symbiotic bacterium, indicating that the prokaryote must replicate synchronically with the host protozoan. In this study, we used light and electron microscopy combined with three-dimensional reconstruction approaches to observe the endosymbiont shape and division during C. deanei cell cycle. We found that the bacterium replicates before the basal body and kinetoplast segregations and that the nucleus is the last organelle to divide, before cytokinesis. In addition, the endosymbiont is usually found close to the host cell nucleus, presenting different shapes during the protozoan cell cycle. Considering that the endosymbiosis in trypanosomatids is a mutualistic relationship, which resembles organelle acquisition during evolution, these findings establish an excellent model for the understanding of mechanisms related with the establishment of organelles in eukaryotic cells.     

Style morphological diversity of some Asteraceae species from Argentina: systematic and functional implications

Stylar micromorphological diversity of 42 Asteraceae species from Argentina was analysed considering species phylogenetic membership and some floral reproductive functions (pollen presentation and pollen reception). In particular, the morphology and organisation of pollen presenter (sweeping hairs) and pollen receptive structures (stigmatic papillae) were described. Results showed that style morphology of the studied species is far more diverse than the categories previously established for Asteraceae, and that it is problematic to relate the sweeping-hair arrangement of species to the only three modes of pollen presentation described for the family, indicating that the hypothesised relationship could be more complex than was formerly thought. For all species with di- or trimorphic florets, the styles of female florets were more slender and without or with more reduced sweeping hairs than the styles of hermaphrodite florets, and divergences of sweeping hair arrangements and morphology were higher among phylogenetically related species. These results suggest that functional aspects of floral morphology seem to be more important than phylogenetic constraints as selective forces determining stylar pollen presentation structures. In contrast, stigmatic-area organisation as well as the morphology of stigmatic papillae remain identical between female and hermaphrodite florets and among phylogenetically related species. Thus, stigmatic papilla morphology seems to be a phylogenetically constrained character in the studied species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Photooxidation of pterin in aqueous solutions: biological and biomedical implications

Studies of the photochemical reactivity of pterin (= 2-aminopteridin-4(3H)-one; PT) in acidic (pH 5.0-6.0) and alkaline (pH 10.2-10.8) aqueous solutions have been performed. The photochemical reactions were followed by UV/VIS spectrophotometry, thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), and an enzymatic method for H2O2 determination. PT is not light-sensitive in the absence of molecular oxygen, but it undergoes photooxidation in the presence of O2, yielding several nonpteridinic products. The quantum yields for PT disappearance were found to be 8.2 (+/-0.6) x 10(-4) and 1.2 (+/-0.2) x 10(-3) in acidic and alkaline media, respectively. H2O2 was detected and quantified in irradiated solutions of PT; and its importance from a biomedical point of view is discussed. The rate constant of the chemical reaction between singlet oxygen ((1)O2) and PT was determined to be 2.5 (+/-0.2) x 10(5) l mol(-1) s(-1) in alkaline medium, and the role of (1)O2 in the photooxidation of pterin was evaluated.     

Growth differentiation factor 9 regulates expression of the bone morphogenetic protein antagonist gremlin

Growth differentiation factor 9 (GDF9) is an oocyte-expressed member of the transforming growth factor beta (TGF-beta) superfamily and is required for normal ovarian follicle development and female fertility. GDF9 acts as a paracrine factor and affects granulosa cell physiology. Only a few genes regulated by GDF9 are known. Our microarray analysis has identified gremlin as one of the genes up-regulated by GDF9 in cultures of granulosa cells. Gremlin is a known member of the DAN family of bone morphogenetic protein (BMP) antagonists, but its expression and function in the ovary are unknown. We have investigated the regulation of gremlin in mouse granulosa cells by GDF9 as well as other members of the TGF-beta superfamily. GDF9 and BMP4 induce gremlin, but TGF-beta does not. In addition, in cultures of granulosa cells, gremlin negatively regulates BMP4 signaling but not GDF9 activity. The expression of gremlin in the ovary was also examined by in situ hybridization. A distinct change in gremlin mRNA compartmentalization occurs during follicle development and ovulation, indicating a highly regulated expression pattern during folliculogenesis. We propose that gremlin modulates the cross-talk between GDF9 and BMP signaling that is necessary during follicle development because both ligands use components of the same signaling pathway.     

Follistatin regulates enamel patterning in mouse incisors by asymmetrically inhibiting BMP signaling and ameloblast differentiation

Rodent incisors are covered by enamel only on their labial side. This asymmetric distribution of enamel is instrumental to making the cutting edge sharp. Enamel matrix is secreted by ameloblasts derived from dental epithelium. Here we show that overexpression of follistatin in the dental epithelium inhibits ameloblast differentiation in transgenic mouse incisors, whereas in follistatin knockout mice, ameloblasts differentiate ectopically on the lingual enamel-free surface. Consistent with this, in wild-type mice, follistatin was continuously expressed in the lingual dental epithelium but downregulated in the labial epithelium. Experiments on cultured tooth explants indicated that follistatin inhibits the ameloblast-inducing activity of BMP4 from the underlying mesenchymal odontoblasts and that follistatin expression is induced by activin from the surrounding dental follicle. Hence, ameloblast differentiation is regulated by antagonistic actions of BMP4 and activin A from two mesenchymal cell layers flanking the dental epithelium, and asymmetrically expressed follistatin regulates the labial-lingual patterning of enamel formation.