Perspectives on environmental adaptability and physiological polymorphism in thermoregulation

The environmental adaptability of human beings has progressed according to various environments experienced in the course of evolution. Therefore, various phenotypes for environmental adaptability exist and are considered to be physiological polymorphism. Physiological polymorphism in thermoregulation is influenced by genotype, individual characteristics, environmental factors, cultural factors, etc. Moreover, it is thought that physiological polymorphism is evidenced more clearly in physiological responses to extreme situations and/or changing conditions than in environments where homeostasis is easily maintained. In the field of physiological anthropology, I think that it is important not only to discover the physiological responses that demonstrate polymorphism, but also to hypothesize about the mechanisms and the processes by which such polymorphisms were formed, and their meaning for human beings. Such discussions may be supposed to lead to an evaluation of the environmental adaptability of humans from the viewpoint of physiological anthropology.     

The role of balancing selection and overdominance in maintaining allozyme polymorphism

Three approaches to the estimation of the role of balancing selection in maintaining allozyme polymorphism are considered: 1) Analysis of the stationary distributions of allelic frequencies in a native subdivided population; 2) Comparison of the genotypic distributions at the early and late developmental stages in successive generations of the same population; 3) Analysis of the joint variability of monogenic and polygenic traits.The conclusion is drawn that allozyme polymorphism must not be regarded as a transient phase of molecular evolution but as its stationary phase. The mechanisms responsible for supporting such stability are discussed.     

Glutathione in plants: biosynthesis and physiological role in environmental stress tolerance

Glutathione (GSH; γ-glutamyl-cysteinyl-glycine) is a small intracellular thiol molecule which is considered as a strong non-enzymatic antioxidant. Glutathione regulates multiple metabolic functions; for example, it protects membranes by maintaining the reduced state of both α-tocopherol and zeaxanthin, it prevents the oxidative denaturation of proteins under stress conditions by protecting their thiol groups, and it serves as a substrate for both glutathione peroxidase and glutathione S-transferase. By acting as a precursor of phytochelatins, GSH helps in the chelating of toxic metals/metalloids which are then transported and sequestered in the vacuole. The glyoxalase pathway (consisting of glyoxalase I and glyoxalase II enzymes) for detoxification of methylglyoxal, a cytotoxic molecule, also requires GSH in the first reaction step. For these reasons, much attention has recently been directed to elucidation of the role of this molecule in conferring tolerance to abiotic stress. Recently, this molecule has drawn much attention because of its interaction with other signaling molecules and phytohormones. In this review, we have discussed the recent progress in GSH biosynthesis, metabolism and its role in abiotic stress tolerance.     

Nuisance growth of Juncus bulbosus: the roles of genetics and environmental drivers tested in a large‐scale survey

1. Invasive species can transform aquatic ecosystems, and the nuisance growth of the freshwater macrophyte Juncus bulbosus has become a problem in many lakes and rivers in northern Europe. It affects biodiversity strongly and conflicts with human uses, not least compromising the generation of hydroelectricity. The causes of the proliferation of these massive stands of J. bulbosus are not finally resolved, however. 2. In this study, a wide range of catchment, lake and sediment parameters (n = 34) were assessed for 139 lakes in Southern Norway, with the aim of explaining the presence or absence of J. bulbosus and to assess potential drivers behind its prolific growth. 3. Juncus bulbosus was more often present in lakes with lower pH and phosphate concentrations, and a higher element ratio of dissolved inorganic nitrogen (DIN) to total phosphorus (DIN : TotP). 4. Despite the many parameters measured across substantial environmental gradients, none explained nuisance growth. Genetic screening (amplified fragment length polymorphism fingerprinting) of plants from a subset of lakes and additional river sites also showed no genetic differences between the various growth forms. A macrophyte trophic index, however, suggested that the most problematic growth occurred in the most oligotrophic lakes. 5. The lack of consistent patterns may reflect either factors not assessed in our survey, or that the current extension of stands represents a gradual cumulative response over time, not characterised effectively in our snapshot survey. Nevertheless, we can now exclude some putative causes of nuisance growth, including in particular genetics and N‐deposition.     

Non-gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism

The relative roles that geographical isolation and selection play in driving population divergence remain one of the central questions in evolutionary biology. We approached this question by investigating genetic and morphological variation among populations of the strawberry poison frog, Dendrobates pumilio, in the Bocas del Toro archipelago, Panama. We found significant population genetic structure and isolation by distance based on amplified fragment length polymorphism markers. Snout vent length (SVL), coloration and the extent and size of dorsal black spots showed large variation among the studied populations. Differences in SVL correlated with genetic distance, whereas black spot patterns and other coloration parameters did not. Indeed, the latter characters were observed to be dramatically different between contiguous populations located on the same island. These results imply that neutral divergence among populations may account for the genetic patterns based on amplified fragment length polymorphism markers and SVL. However, selective pressures need to be invoked in order to explain the extraordinary variation in spot size and coverage, and coloration. We discuss the possibility that the observed variation in colour morphs is a consequence of a combination of local variation in both natural selection on an aposematic signal towards visual predators and sexual selection generated by colour morph-specific mate preferences.     

Multivariate phenotypes and the potential for alternative phenotypic optima in wall lizard (Podarcis muralis) ventral colour morphs

A major goal in evolutionary biology is to determine how phenotypic variation arises and is maintained in natural populations. Recent studies examining the morphological, physiological and behavioural differences among discrete colour morphotypes (morphs) have revealed several mechanisms that maintain discrete variation within populations, including frequency‐dependence, density‐dependence and correlational selection. For example, trade‐offs over resource allocation to morphological, physiological and behavioural traits can drive correlational selection for morph‐specific phenotypic optima. Here, we describe a ventral colour polymorphism in the wall lizard (Podarcis muralis) and test the hypothesis that morphs differ along multivariate axes defined by trade‐offs in morphological, physiological, and immunological traits. We show that ventral colour is a discrete trait and that morphs differ in body size, prevalence of infection by parasites and infection intensity. We also find that morphs differ along multivariate phenotypic axes and experience different multivariate selection pressures. Our results suggest that multivariate selection pressures may favour alternative optimal morph‐specific phenotypes in P. muralis.     

Periodicity and environmental drivers of apical and lateral growth in a Cerrado woody species

Key message

Apical and lateral growth are seasonal in a Cerrado species, and these events are related to each other and linked with climatic and environmental features.

Abstract

In the Cerrado, a tropical ecosystem with seasonal rainfall, we investigated the timing of leaf production and cambial activity, and checked whether these features are related to each other and with climatic and environmental factors. Between September 2011 and December 2012, sampling of main stem and vegetative phenological observations of Kielmeyera grandiflora (Wawra) Saddi (Calophyllaceae) were done monthly to assess seasonality in leaf production and cambial activity, and to compare these features with each other. To check the relationship of bud opening and the onset of cambial activity with climatic and environmental features, the average temperature and day length, and the precipitation sum in a time window ranging from 1 to 30 days before the occurrence of these events were recorded, and the coefficient of variation was calculated. Leaf production and cambial activity were seasonal. Bud opening occurred in September 2011 and August 2012, during the dry season. The onset of cambial activity occurred in October both in 2011 and 2012, 1–2 months after bud opening, at the beginning of the rainy season. The cambium was dormant in May, during the rainy season. Photoperiod and temperature showed low coefficients of variation in the time window before bud opening and onset of cambial activity, while rainfall presented a high coefficient of variation. Thus, both apical and lateral growth are seasonal events in Cerrado species, and are related to each other. A set of climatic and environmental features is related with seasonal growth, among which photoperiod and temperature may be important in the regulation of these events.

     

Biogeographical determinants for total and endemic species richness in a continental archipelago

We examined the relationship between plant species richness and biogeographical variables (island area, island maximum elevation, distance from nearest inhabited island, distance from nearest mainland) using a data set comprising 201 islands of the Aegean archipelago. We found that endemic species richness was strongly correlated to total species richness. Single-island endemic species richness was most strongly correlated to island maximum elevation, and then to island area, with an apparent small island effect for islands smaller than 47 km². Total species richness was most strongly correlated to island area (with no apparent small island effect), and less strongly correlated to island maximum elevation. Distance from the mainland or other inhabited islands displayed limited predictive value in our data set. The slope of the relationship between species richness and geographical factors (island area, elevation, distance from island/mainland) was steeper for endemic species richness than for total richness. Finally, the different scales of endemicity (single-island endemics, island group endemics and Aegean regional endemics) displayed similar qualitative trends and only differed quantitatively. Thus, we conclude that different biogeographical factors act as drivers for total species richness than for endemic species richness.     

A role for myelin-associated peroxisomes in maintaining paranodal loops and axonal integrity

Demyelinating diseases of the nervous system cause axon loss but the underlying mechanisms are not well understood. Here we show by confocal and electron microscopy that in myelin-forming glia peroxisomes are associated with myelin membranes. When peroxisome biogenesis is experimentally perturbed in Pex5 conditional mouse mutants, myelination by Schwann cells appears initially normal. However, in nerves of older mice paranodal loops become physically unstable and develop swellings filled with vesicles and electron-dense material. This novel model of a demyelinating neuropathy demonstrates that peroxisomes serve an important function in the peripheral myelin compartment, required for long-term axonal integrity.     

A functional genomic screen identifies a role for TAO1 kinase in spindle-checkpoint signalling

Defects in chromosome-microtubule attachment trigger spindle-checkpoint activation and delay mitotic progression. How microtubule attachment is sensed and integrated into the steps of checkpoint-signal amplification is poorly understood. In a functional genomic screen targeting human kinases and phosphatases, we identified a microtubule affinity-regulating kinase kinase, TAO1 (also known as MARKK) as an important regulator of mitotic progression, required for both chromosome congression and checkpoint-induced anaphase delay. TAO1 interacts with the checkpoint kinase BubR1 and promotes enrichment of the checkpoint protein Mad2 at sites of defective attachment, providing evidence for a regulatory step that precedes the proposed Mad2-Mad1 dependent checkpoint-signal amplification step. We propose that the dual functions of TAO1 in regulating microtubule dynamics and checkpoint signalling may help to coordinate the establishment and monitoring of correct congression of chromosomes, thereby protecting genomic stability in human cells.     

DNA topology in chromosomes: a quantitative survey and its physiological implications

Using a simple geometric model, we propose a general method for computing the linking number of the DNA embedded in chromatin fibers. The relevance of the method is reviewed through the single molecule experiments that have been performed in vitro with magnetic tweezers. We compute the linking number of the DNA in the manifold conformational states of the nucleosome which have been evidenced in these experiments and discuss the functional dynamics of chromosomes in the light of these manifold states.     

Regulation of respiration in plants: a role for alternative metabolic pathways

Respiratory metabolism includes the reactions of glycolysis, the tricarboxylic acid cycle and the mitochondrial electron transport chain, but is also directly linked with many other metabolic pathways such as protein and lipid biosynthesis and photosynthesis via photorespiration. Furthermore, any change in respiratory activity can impact the redox status of the cell and the production of reactive oxygen species. In this review, it is discussed how respiration is regulated and what alternative pathways are known that increase the metabolic flexibility of this vital metabolic process. By looking at the adaptive responses of respiration to hypoxia or changes in the oxygen availability of a cell, the integration of regulatory responses of various pathways is illustrated.     

An RNA interference phenotypic screen identifies a role for FGF signals in colon cancer progression

In tumor cells, stepwise oncogenic deregulation of signaling cascades induces alterations of cellular morphology and promotes the acquisition of malignant traits. Here, we identified a set of 21 genes, including FGF9, as determinants of tumor cell morphology by an RNA interference phenotypic screen in SW480 colon cancer cells. Using a panel of small molecular inhibitors, we subsequently established phenotypic effects, downstream signaling cascades, and associated gene expression signatures of FGF receptor signals. We found that inhibition of FGF signals induces epithelial cell adhesion and loss of motility in colon cancer cells. These effects are mediated via the mitogen-activated protein kinase (MAPK) and Rho GTPase cascades. In agreement with these findings, inhibition of the MEK1/2 or JNK cascades, but not of the PI3K-AKT signaling axis also induced epithelial cell morphology. Finally, we found that expression of FGF9 was strong in a subset of advanced colon cancers, and overexpression negatively correlated with patients' survival. Our functional and expression analyses suggest that FGF receptor signals can contribute to colon cancer progression.