Floral and vegetative morphometrics of three Platonia insignis Mart. (Clusiaceae) populations,a native tree from the Brazilian Amazon

Platonia insignis Mart. (Clusiaceae), the bacurizeiro, is a native tree species from the Brazilian Amazon forests. Three populations of P. insignis have been observed in the north-east region of the state of Maranhão that differ in flower color: the red population that produces dark pink flowers, the pink population that produces light pink flowers, and the white population with yellowish-white flowers. From multivariate statistical analysis, we aimed at characterizing such populations using morpho-anatomical leaf and flower morphology parameters. A total of 40 P. insignis individuals have been sampled in the cities of São Luís and Chapadinha. The morphological traits varied more than the anatomical traits. Area, fresh mass, and dry mass were the leaf parameters that show more variations. Platonia insignis have hypostomatic or amphihypostomatic leaves. The length of the gynoecium+the length of the nectary, the total length and the length of gynoecium were the principal components considering flower analysis. The three populations did not show significant differences nor did they group using Ward's method. Individuals from the Chapadinha and São Luís red population have been separated according to leaf and flower morphological traits, and the morphological difference between individuals may represent early stages of geographical speciation.     

Leaflet morphometric variation of service tree (Sorbus domestica L.) in the Balkan Peninsula

Abstract

In most European countries, the service tree (Sorbus domestica L.) is a rare and threatened species and its conservation has been recognised as a priority. The aim of this study was to asses its morphologic variation in the western and central part of the Balkan Peninsula and in southern Central Europe. Three populations were analysed: one in Serbia, one in Bosnia and Herzegovina and one in Slovenia. In each population 30 trees were selected, and from each tree 30 leaves were collected for morphometric analysis based on nine leaflet morphological traits. Univariate (ANOVA) and multivariate (MANOVA) analysis of variance were used to estimate the variation within- and between populations and a discriminant analysis was performed to examine the structure of the between-population differences. The values of particular morphological traits found in our study did not differ considerably from the values reported elsewhere. The results revealed significant within- and between population variation. Variation within populations was highly significant for all the scored leaf morphological traits, while variation between populations was significant for all the studied traits except for the leaflet length. The discrimination between the three populations was significant. High percentages of correctly classified samples demonstrate good discriminating employability of the analysed leaf morphological traits and indicate differentiation of the analysed populations.     

Acclimation responses to temperature vary with vertical stratification: implications for vulnerability of soil‐dwelling species to extreme temperature events

The occurrence of summer heat waves is predicted to increase in amplitude and frequency in the near future, but the consequences of such extreme events are largely unknown, especially for belowground organisms. Soil organisms usually exhibit strong vertical stratification, resulting in more frequent exposure to extreme temperatures for surface‐dwelling species than for soil‐dwelling species. Therefore soil‐dwelling species are expected to have poor acclimation responses to cope with temperature changes. We used five species of surface‐dwelling and four species of soil‐dwelling Collembola that habituate different depths in the soil. We tested for differences in tolerance to extreme temperatures after acclimation to warm and cold conditions. We also tested for differences in acclimation of the underlying physiology by looking at changes in membrane lipid composition. Chill coma recovery time, heat knockdown time and fatty acid profiles were determined after 1 week of acclimation to either 5 or 20 °C. Our results showed that surface‐dwelling Collembola better maintained increased heat tolerance across acclimation temperatures, but no such response was found for cold tolerance. Concordantly, four of the five surface‐dwelling Collembola showed up to fourfold changes in relative abundance of fatty acids after 1 week of acclimation, whereas none of the soil‐dwelling species showed a significant adjustment in fatty acid composition. Strong physiological responses to temperature fluctuations may have become redundant in soil‐dwelling species due to the relative thermal stability of their subterranean habitat. Based on the results of the four species studied, we expect that unless soil‐dwelling species can temporarily retreat to avoid extreme temperatures, the predicted increase in heat waves under climatic change renders these soil‐dwelling species more vulnerable to extinction than species with better physiological capabilities. Being able to act under a larger thermal range is probably costly and could reduce maximum performance at the optimal temperature.     

Contrasting effects of climate change in continental vs. oceanic environments on population persistence and microevolution of Atlantic salmon

Facing climate change (CC), species are prone to multiple modifications in their environment that can lead to extinction, migration or adaptation. Identifying the role and interplay of different potential stressors becomes a key question. Anadromous fishes will be exposed to both river and oceanic habitat changes. For Atlantic salmon, the river water temperature, river flow and oceanic growth conditions appear as three main stressing factors. They could act on population dynamics or as selective forces on life‐history pathways. Using an individual‐based demo‐genetic model, we assessed the effects of these factors (1) to compare risks of extinction resulting from CC in river and ocean, and (2) to assess CC effects on life‐history pathways including the evolution of underlying genetic control of phenotypic plasticity. We focused on Atlantic salmon populations from Southern Europe for a time horizon of three decades. We showed that CC in river alone should not lead to extinction of Southern European salmon populations. In contrast, the reduced oceanic growth appeared as a significant threat for population persistence. An increase in river flow amplitude increased the risk of local extinction in synergy with the oceanic effects, but river temperature rise reduced this risk. In terms of life‐history modifications, the reduced oceanic growth increased the age of return of individuals through plastic and genetic responses. The river temperature rise increased the proportion of sexually mature parr, but the genetic evolution of the maturation threshold lowered the maturation rate of male parr. This was identified as a case of environmentally driven plastic response that masked an underlying evolutionary response of plasticity going in the opposite direction. We concluded that to counteract oceanic effects, river flow management represented the sole potential force to reduce the extinction probability of Atlantic salmon populations in Southern Europe, although this might not impede changes in migration life history.     

Wnt signaling regulates experience-dependent synaptic plasticity in the adult nervous system

Comment on: Jensen M, et al. Cell 2012; 149:173-87.     

Possible mechanisms of synaptic plasticity modulation by extremely low-frequency magnetic fields

Understanding the biological mechanisms by which extremely low-frequency (ELF, < 300 Hz) magnetic fields (MFs) interact with human brain activity is an active field of research. Such knowledge is required by international agencies providing guidelines for general public and workers exposure to ELF MFs (such as ICNIRP, the International Commission on Non-Ionizing Radiation Protection). The identification of these interaction mechanisms is extremely challenging, since the effects of ELF MF exposure need to be monitored and understood at very different spatial (from micrometers to centimeters) and temporal (from milliseconds to minutes) scales. One possibility to overcome these issues is to develop biophysical models, based on the systems of mathematical equations describing the electric or metabolic activity of the brain tissue. Biophysical models of the brain activity offer the possibility to simulate how the brain tissue interacts with ELF MFs, in order to gain new insights into experimental data, and to test novel hypotheses regarding interaction mechanisms. This paper presents novel hypotheses regarding the effects of power line (60 Hz in North America) MFs on human brain activity, with arguments from biophysical models. We suggest a hypothetic chain of events that could bridge MF exposure with detectable effects on human neurophysiology. We also suggest novel directions of research in order to reach a convergence of biophysical models of brain activity and corresponding experimental data to identify interaction mechanisms.     

Somatic cell transformation into stem cell-like cells induced by different microenvironments

Development of induced pluripotent stem cell (iPSC) technology introduced a novel way to derive pluripotent stem cells, but the genetic manipulation required to generate iPSCs may lead to uncontrolled tumorigenesis of the established cells and thus limit clinical feasibility of the technology. Numerous attempts have been made to date, and alternative reprogramming of somatic cells to reactivate cellular plasticity after differentiation has been suggested. As a result, it had become clear that cell-to-cell interactions and specific acellular environments can be utilized for somatic cell reprogramming. In our previous studies, embryonic stem cell (ESC)-like cells could be derived from transforming ovarian cells and fetal fibroblasts by cell-to-cell interaction or specific cell-mediated microenvironmental factor(s). This cellular event was induced without undertaking genetic manipulation of progenitor cells. Several differences were found between the cellular properties of niche-induced, ESC-like cells and those of genetically manipulated iPSCs and the referenced ESCs. Thus, we provided evidence that terminally differentiated somatic cells either acquire pluripotency-like activity or possess cellular and genetic plasticity under a specific microenvironment and/or cell-to-cell interaction. In this minireview, we discuss derivation of stem cell-like cells under specific microenvironmental conditions in terms of technical perspectives and limitations.     

Impaired cognitive function and reduced anxiety‐related behavior in a promyelocytic leukemia (PML) tumor suppressor protein‐deficient mouse

The promyelocytic leukemia (PML) protein is a tumor suppressor factor mostly known by its involvement in acute promyelocytic leukemia (APL). Interestingly, recent studies have provided evidence that, in the central nervous system, PML is involved in neurogenesis. However, prospective studies of PML in brain are lacking. To further understand the role of PML in the mammalian brain, we studied plasticity and behavioral changes in PML knockout mice. If PML is involved in neurogenesis, and neurogenesis is an important process for proper brain development as well as learning and memory functions, we hypothesized that PML might have a role in plasticity and cognition. Behavioral studies demonstrated that PML knockout mice present abnormalities in conditioned learning and spatial memory, as determined by fear conditioning and Morris water maze tasks. Experiments to determine normal exploratory behavior interestingly revealed that PML knockout mice present reduced anxiety‐related responses as compared to control animals. This was confirmed when PML knockout mice spent more time in the open arms of an elevated plus‐maze, which is an indication of decreased anxiety. Additionally, impairments in hippocampus‐dependent learning were mirrored by altered long‐term plasticity at Schaffer collateral‐CA1 synapses. We now provide the first evidence for an important role of PML in the brain, indicating that PML might have a role in synaptic plasticity and associated behavioral processes.