Gene Flow and Maintenance of Genetic Diversity in Invasive Mosquitofish (Gambusia holbrooki)

Genetic analyses contribute to studies of biological invasions by mapping the origin and dispersal patterns of invasive species occupying new territories. Using microsatellite loci, we assessed the genetic diversity and spatial population structure of mosquitofish (Gambusia holbrooki) that had invaded Spanish watersheds, along with the American locations close to the suspected potential source populations. Mosquitofish populations from the Spanish streams that were studied had similar levels of genetic diversity to the American samples; therefore, these populations did not appear to have undergone substantial losses of genetic diversity during the invasion process. Population structure analyses indicated that the Spanish populations fell into four main clusters, which were primarily associated with hydrography. Dispersal patterns indicated that local populations were highly connected upstream and downstream through active dispersal, with an average of 21.5% fish from other locations in each population. After initially introducing fish to one location in a given basin, such dispersal potential might contribute to the spread and colonization of suitable habitats throughout the entire river basin. The two-dimension isolation-by-distance pattern here obtained, indicated that the human-mediated translocation of mosquitofish among the three study basins is a regular occurrence. Overall, both phenomena, high natural dispersal and human translocation, favor gene flow among river basins and the retention of high genetic diversity, which might help retain the invasive potential of mosquitofish populations.     

Differential Growth Responses to Water Balance of Coexisting Deciduous Tree Species Are Linked to Wood Density in a Bolivian Tropical Dry Forest

A seasonal period of water deficit characterizes tropical dry forests (TDFs). There, sympatric tree species exhibit a diversity of growth rates, functional traits, and responses to drought, suggesting that each species may possess different strategies to grow under different conditions of water availability. The evaluation of the long-term growth responses to changes in the soil water balance should provide an understanding of how and when coexisting tree species respond to water deficit in TDFs. Furthermore, such differential growth responses may be linked to functional traits related to water storage and conductance. We used dendrochronology and climate data to retrospectively assess how the radial growth of seven coexisting deciduous tree species responded to the seasonal soil water balance in a Bolivian TDF. Linear mixed-effects models were used to quantify the relationships between basal area increment and seasonal water balance. We related these relationships with wood density and sapwood production to assess if they affect the growth responses to climate. The growth of all species responded positively to water balance during the wet season, but such responses differed among species as a function of their wood density. For instance, species with a strong growth response to water availability averaged a low wood density which may facilitate the storage of water in the stem. By contrast, species with very dense wood were those whose growth was less sensitive to water availability. Coexisting tree species thus show differential growth responses to changes in soil water balance during the wet season. Our findings also provide a link between wood density, a trait related to the ability of trees to store water in the stem, and wood formation in response to water availability.     

Postprandial changes in the proteome are modulated by dietary fat in patients with metabolic syndrome

Metabolic syndrome is a multicomponent disorder whose etiology is the result of a complex interaction between genetic, metabolic and environmental factors including dietary habits. Our aim was to identify proteome–diet interactions during the postprandial state after the acute intake of four meals with different qualities of fat in the proteome of peripheral blood mononuclear cells. A randomized controlled trial conducted within the LIPGENE study assigned 39 metabolic syndrome patients to one of four meals: a high-saturated-fatty-acid (HSFA) meal, a high-monounsaturated-fatty-acid (HMUFA) meal and two high-polyunsaturated-fatty-acid (from walnut) (HPUFA) meals supplemented with n-3 PUFA or placebo. We analyzed the postprandial changes in the whole proteome of both nuclear and cytoplasmic fractions of peripheral blood mononuclear cells by two-dimensional proteomics. Twenty-three proteins were differentially expressed. HSFA intake caused the postprandial increase of proteins responding to oxidative stress (HSPA1A, PDIA3 and PSME1) and DNA damage (SMC6), whereas HMUFA intake led to the up-regulation of HSPA1A and PDIA3. HPUFA meal supplementation with n-3 PUFA produced peroxisomal beta-oxidation inhibition by down-regulation of ECH1, a process related to insulin signaling improvement. In conclusion, HSFA meal intake causes deleterious postprandial changes in the proteome in terms of DNA damage and procoagulant state, which reflect a higher postprandial oxidative stress after HSFA meal intake as compared to intake of HMUFA and HPUFA meals. Moreover, the addition of long-chain n-3 PUFA to an HPUFA meal may improve insulin signaling and exerts an anti-inflammatory effect when compared to an HPUFA meal.     

How do bryophytes govern generative recruitment of vascular plants?

Interactions between vascular plants and bryophytes determine plant community composition in many ecosystems. Yet, little is known about the importance of interspecific differences between bryophytes with respect to their effects on vascular plants. We compared the extent to which species-specific bryophyte effects on vascular plant generative recruitment depend on the following underlying mechanisms: allelopathy, mechanical obstruction, soil moisture and temperature control. We sowed 10 vascular plant species into monospecific mats of six chemically and structurally diverse bryophytes, and examined 1-yr seedling recruitment. Allelopathic effects were also assessed in a laboratory phyto-assay. Although all bryophytes suppressed vascular plant regeneration, there were significant differences between the bryophyte species. The lack of interactions indicated the absence of species-specific adaptations of vascular plants for recruitment in bryophyte mats. Differences between bryophyte species were best explained by alterations in temperature regime under bryophyte mats, mostly by reduced temperature amplitudes during germination. The temperature regime under bryophyte mats was well predicted by species-specific bryophyte cushion thickness. The fitness of established seedlings was not affected by the presence of bryophytes. Our results suggest that climatically or anthropogenically driven changes in the species' composition of bryophyte communities have knock-on effects on vascular plant populations via generative reproduction.     

Larger brains spur species diversification in birds

Evidence is accumulating that species traits can spur their evolutionary diversification by influencing niche shifts, range expansions, and extinction risk. Previous work has shown that larger brains (relative to body size) facilitate niche shifts and range expansions by enhancing behavioral plasticity but whether larger brains also promote evolutionary diversification is currently backed by insufficient evidence. We addressed this gap by combining a brain size dataset for >1900 avian species worldwide with estimates of diversification rates based on two conceptually different phylogenetic‐based approaches. We found consistent evidence that lineages with larger brains (relative to body size) have diversified faster than lineages with relatively smaller brains. The best supported trait‐dependent model suggests that brain size primarily affects diversification rates by increasing speciation rather than decreasing extinction rates. In addition, we found that the effect of relatively brain size on species‐level diversification rate is additive to the effect of other intrinsic and extrinsic factors. Altogether, our results highlight the importance of brain size as an important factor in evolution and reinforce the view that intrinsic features of species have the potential to influence the pace of evolution.     

Transient Exposure to Ethanol during Zebrafish Embryogenesis Results in Defects in Neuronal Differentiation: An Alternative Model System to Study FASD

Background

The exposure of the human embryo to ethanol results in a spectrum of disorders involving multiple organ systems, including the impairment of the development of the central nervous system (CNS). In spite of the importance for human health, the molecular basis of prenatal ethanol exposure remains poorly understood, mainly to the difficulty of sample collection. Zebrafish is now emerging as a powerful organism for the modeling and the study of human diseases. In this work, we have assessed the sensitivity of specific subsets of neurons to ethanol exposure during embryogenesis and we have visualized the sensitive embryonic developmental periods for specific neuronal groups by the use of different transgenic zebrafish lines.

Methodology/Principal Findings

In order to evaluate the teratogenic effects of acute ethanol exposure, we exposed zebrafish embryos to ethanol in a given time window and analyzed the effects in neurogenesis, neuronal differentiation and brain patterning. Zebrafish larvae exposed to ethanol displayed small eyes and/or a reduction of the body length, phenotypical features similar to the observed in children with prenatal exposure to ethanol. When neuronal populations were analyzed, we observed a clear reduction in the number of differentiated neurons in the spinal cord upon ethanol exposure. There was a decrease in the population of sensory neurons mainly due to a decrease in cell proliferation and subsequent apoptosis during neuronal differentiation, with no effect in motoneuron specification.

Conclusion

Our investigation highlights that transient exposure to ethanol during early embryonic development affects neuronal differentiation although does not result in defects in early neurogenesis. These results establish the use of zebrafish embryos as an alternative research model to elucidate the molecular mechanism(s) of ethanol-induced developmental toxicity at very early stages of embryonic development.     

Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

The enzyme isocitrate dehydrogenase (ICDH; EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate, to produce 2-oxoglutarate. The incompleteness of the tricarboxylic acids cycle in marine cyanobacteria confers a special importance to isocitrate dehydrogenase in the C/N balance, since 2-oxoglutarate can only be metabolized through the glutamine synthetase/glutamate synthase pathway. The physiological regulation of isocitrate dehydrogenase was studied in cultures of Prochlorococcus sp. strain PCC 9511, by measuring enzyme activity and concentration using the NADPH production assay and Western blotting, respectively. The enzyme activity showed little changes under nitrogen or phosphorus starvation, or upon addition of the inhibitors DCMU, DBMIB and MSX. Azaserine, an inhibitor of glutamate synthase, induced clear increases in the isocitrate dehydrogenase activity and icd gene expression after 24 h, and also in the 2-oxoglutarate concentration. Iron starvation had the most significant effect, inducing a complete loss of isocitrate dehydrogenase activity, possibly mediated by a process of oxidative inactivation, while its concentration was unaffected. Our results suggest that isocitrate dehydrogenase responds to changes in the intracellular concentration of 2-oxoglutarate and to the redox status of the cells in Prochlorococcus.     

Hypoxic fed-batch cultivation of Pichia pastoris increases specific and volumetric productivity of recombinant proteins

High cell density cultivation of Pichia pastoris has to cope with several technical limitations, most importantly the transfer of oxygen. By applying hypoxic conditions to chemostat cultivations of P. pastoris expressing an antibody Fab fragment under the GAP promoter, a 2.5-fold increase of the specific productivity q(P) at low oxygen supply was observed. At the same time the biomass decreased and ethanol was produced, indicating a shift from oxidative to oxidofermentative conditions. Based on these results we designed a feedback control for enhanced productivity in fed batch processes, where the concentration of ethanol in the culture was kept constant at approximately 1.0% (vv(-1)) by a regulated addition of feed medium. This strategy was tested successfully with three different protein producing strains, leading to a three- to sixfold increase of the q(P) and threefold reduced fed batch times. Taken together the volumetric productivity Q(P) increased 2.3-fold.