Energetics and the evolution of carnivorous plants--Darwin's 'most wonderful plants in the world'

Carnivory has evolved independently at least six times in five angiosperm orders. In spite of these independent origins, there is a remarkable morphological convergence of carnivorous plant traps and physiological convergence of mechanisms for digesting and assimilating prey. These convergent traits have made carnivorous plants model systems for addressing questions in plant molecular genetics, physiology, and evolutionary ecology. New data show that carnivorous plant genera with morphologically complex traps have higher relative rates of gene substitutions than do those with simple sticky traps. This observation suggests two alternative mechanisms for the evolution and diversification of carnivorous plant lineages. The 'energetics hypothesis' posits rapid morphological evolution resulting from a few changes in regulatory genes responsible for meeting the high energetic demands of active traps. The 'predictable prey capture hypothesis' further posits that complex traps yield more predictable and frequent prey captures. To evaluate these hypotheses, available data on the tempo and mode of carnivorous plant evolution were reviewed; patterns of prey capture by carnivorous plants were analysed; and the energetic costs and benefits of botanical carnivory were re-evaluated. Collectively, the data are more supportive of the energetics hypothesis than the predictable prey capture hypothesis. The energetics hypothesis is consistent with a phenomenological cost-benefit model for the evolution of botanical carnivory, and also accounts for data suggesting that carnivorous plants have leaf construction costs and scaling relationships among leaf traits that are substantially different from those of non-carnivorous plants.

Multiple chromosomal rearrangements structured the ancestral vertebrate Hox-bearing protochromosomes

While the proposal that large-scale genome expansions occurred early in vertebrate evolution is widely accepted, the exact mechanisms of the expansion--such as a single or multiple rounds of whole genome duplication, bloc chromosome duplications, large-scale individual gene duplications, or some combination of these--is unclear. Gene families with a single invertebrate member but four vertebrate members, such as the Hox clusters, provided early support for Ohno's hypothesis that two rounds of genome duplication (the 2R-model) occurred in the stem lineage of extant vertebrates. However, despite extensive study, the duplication history of the Hox clusters has remained unclear, calling into question its usefulness in resolving the role of large-scale gene or genome duplications in early vertebrates. Here, we present a phylogenetic analysis of the vertebrate Hox clusters and several linked genes (the Hox "paralogon") and show that different phylogenies are obtained for Dlx and Col genes than for Hox and ErbB genes. We show that these results are robust to errors in phylogenetic inference and suggest that these competing phylogenies can be resolved if two chromosomal crossover events occurred in the ancestral vertebrate. These results resolve conflicting data on the order of Hox gene duplications and the role of genome duplication in vertebrate evolution and suggest that a period of genome reorganization occurred after genome duplications in early vertebrates.

The phylogenetic significance of anthropoid paranasal sinuses

In this study, the phylogenetic significance of anthropoid paranasal sinus anatomy is explored. New information reported in recent years has precipitated new hypotheses of sinus homology and more than doubled the number of anthropoid genera for which confident assessments of sinus identity can be made. As a result, it is likely that the phylogenetic meaning of commonly cited characters such as the ethmoid and frontal sinuses will change. The traditional method of "character mapping" is employed to test hypotheses of sinus homology and to reconstruct the ancestral states for sinus characters in major anthropoid clades. Results show that most sinuses appear to be primitive retentions in anthropoids, with their absences in various genera representing losses. Accordingly, many of these sinuses are potential anthropoid synapomorphies.

Insect brains use image interpolation mechanisms to recognise rotated objects

Recognising complex three-dimensional objects presents significant challenges to visual systems when these objects are rotated in depth. The image processing requirements for reliable individual recognition under these circumstances are computationally intensive since local features and their spatial relationships may significantly change as an object is rotated in the horizontal plane. Visual experience is known to be important in primate brains learning to recognise rotated objects, but currently it is unknown how animals with comparatively simple brains deal with the problem of reliably recognising objects when seen from different viewpoints. We show that the miniature brain of honeybees initially demonstrate a low tolerance for novel views of complex shapes (e.g. human faces), but can learn to recognise novel views of stimuli by interpolating between or 'averaging' views they have experienced. The finding that visual experience is also important for bees has important implications for understanding how three dimensional biologically relevant objects like flowers are recognised in complex environments, and for how machine vision might be taught to solve related visual problems.

Allometric scaling of infraorbital surface topography in Homo

Infraorbital morphology is often included in phylogenetic and functional analyses of Homo. The inclusion of distinct infraorbital configurations, such as the "canine fossa" in Homo sapiens or the "inflated" maxilla in Neandertals, is generally based on either descriptive or qualitative assessments of this morphology, or simple linear chord and subtense measurements. However, the complex curvilinear surface of the infraorbital region has proven difficult to quantify through these traditional methods. In this study, we assess infraorbital shape and its potential allometric scaling in fossil Homo (n=18) and recent humans (n=110) with a geometric morphometric method well-suited for quantifying complex surface topographies. Our results indicate that important aspects of infraorbital shape are correlated with overall infraorbital size across Homo. Specifically, individuals with larger infraorbital areas tend to exhibit relatively flatter infraorbital surface topographies, taller and narrower infraorbital areas, sloped inferior orbital rims, anteroinferiorly oriented maxillary body facies, posteroinferiorly oriented maxillary processes of the zygomatic, and non-everted lateral nasal margins. In contrast, individuals with smaller infraorbital regions generally exhibit relatively depressed surface topographies, shorter and wider infraorbital areas, projecting inferior orbital rims, posteroinferiorly oriented maxillary body facies, anteroinferiorly oriented maxillary processes, and everted lateral nasal margins. These contrasts form a continuum and only appear dichotomized at the ends of the infraorbital size spectrum. In light of these results, we question the utility of incorporating traditionally polarized infraorbital morphologies in phylogenetic and functional analyses without due consideration of continuous infraorbital and facial size variation in Homo. We conclude that the essentially flat infraorbital surface topography of Neandertals is not unique and can be explained, in part, as a function of possessing large infraorbital regions, the ancestral condition for Homo. Furthermore, it appears likely that the diminutive infraorbital region of anatomically modern Homo sapiens is a primary derived trait, with related features such as depressed infraorbital surface topography expressed as correlated secondary characters.

Contrasted patterns of hyperdiversification in Mediterranean hotspots

Dating the Tree of Life has now become central to relating patterns of biodiversity to key processes in Earth history such as plate tectonics and climate change. Regions with a Mediterranean climate have long been noted for their exceptional species richness and high endemism. How and when these biota assembled can only be answered with a good understanding of the sequence of divergence times for each of their components. A critical aspect of dating by using molecular sequence divergence is the incorporation of multiple suitable age constraints. Here, we show that only rigorous phylogenetic analysis of fossil taxa can lead to solid calibration and, in turn, stable age estimates, regardless of which of 3 relaxed clock-dating methods is used. We find that Proteaceae, a model plant group for the Mediterranean hotspots of the Southern Hemisphere with a very rich pollen fossil record, diversified under higher rates in the Cape Floristic Region and Southwest Australia than in any other area of their total distribution. Our results highlight key differences between Mediterranean hotspots and indicate that Southwest Australian biota are the most phylogenetically diverse but include numerous lineages with low diversification rates.

The OrcPI locus: genomic organization, expression pattern, and noncoding regions variability in Orchis italica (Orchidaceae) and related species

OrcPI is a class B MADS-box gene of Orchis italica (Orchidaceae), homologous of the PISTILLATA/GLOBOSA gene isolated in Arabidopsis and Antirrhinum. Its role in determining petals and stamens is conserved in orchids, where it seems to be involved also in other functions, such as flower longevity and ovary development. The present study reports the genomic characterization of the OrcPI locus in O. italica including coding and noncoding regions (introns, 5'- and 3' untranslated regions, and putative promoter). Nucleotide polymorphism distribution confirmed that this gene is subjected to different evolutionary forces, phylogenetic and distance analyses demonstrated that OrcPI is a useful nuclear marker at low taxonomic level in orchids. The expression pattern analysis showed that OrcPI transcripts are present in all the floral structures, undetected in the vegetative tissues, and decreased in the natural senescent flower. Finally, micro-RNAs putative target sites were identified within the OrcPI gene, conserved among orchids.

Skull anatomy of the miniaturized gecko Sphaerodactylus roosevelti (Squamata: Gekkota)

A detailed description of the skull and jaw of the gecko Sphaerodactylus roosevelti is presented. The bones are described articulated and isolated with special consideration given to the type of suture among joining elements. S. roosevelti was compared with 109 gekkotan species to evaluate the osteological variation and to find characters for cladistic analysis. Changes in the skull associated with the miniaturization process are discussed within the sphaerodactylid geckos. A noticeable increase of overlapping sutures was observed in the snout of the smallest sphaerodactylids compared to other gekkotans. This pattern is convergent with that in miniaturized pygopodids and may be attributed to adaptations for decreasing mechanical resistance of the cranium during feeding or burrowing. New cranial characters support Sphaerodactylinae as a monophyletic group and should be useful for resolving questions such as their relationship with other gekkotans.

The inhibitory action of kohamaic acid A derivatives on mammalian DNA polymerase beta

We previously isolated a novel natural product, designated kohamaic acid A (KA-A, compound 1), as an inhibitor of the first cleavage of fertilized sea urchin eggs, and found that this compound could selectively inhibit the activities of mammalian DNA polymerases (pols). In this paper, we investigated the structure and bioactivity of KA-A and its chemically synthesized 11 derivatives (i.e., compounds 2-12), including KA-A - fatty acid conjugates. The pol inhibitory activity of compound 11 [(1S*,4aS*,8aS*)-17-(1,4,4a,5,6,7,8,8a-octahydro-2,5,5,8a-tetramethyl-naphthalen-1-yl)heptadecanoic acid] was the strongest among the synthesized compounds, and the range of IC(50) values for mammalian pols was 3.22 to 8.76 microM; therefore, the length of the fatty acid side chain group of KA-A is important for pol inhibition. KA-A derivatives could prevent human cancer cell (promyelocytic leukemia cell line, HL-60) growth with the same tendency as the inhibition of mammalian pols. Since pol beta is the smallest molecule, we used it to analyze the biochemical relationship with KA-A derivatives. From computer modeling analysis (i.e., docking simulation analysis), these compounds bound selectively to four amino acid residues (Leu11, Lys35, His51 and Thr79) of the N-terminal 8-kDa domain of pol beta, and the binding energy between compound 11 and pol beta was largest in the synthesized compounds. The relationship between the three-dimensional molecular structures of KA-A-related compounds and these inhibitory activities is discussed.

Patterns of plant speciation in the Cape floristic region

Plant species have accumulated in the Cape region of southern Africa to a much greater degree than in areas of equivalent size in the rest of the subcontinent. Although this could be a consequence simply of lower extinction rates in the Cape, most researchers have invoked high rates of ecological speciation, driven by unique aspects of the Cape environment, as the primary explanation for this richness. To assess these ideas, we analyzed the frequencies of ecological shifts among 188 sister species pairs obtained from molecular phylogenies of eight Cape clades. Ecological shifts were evident in 80% of sister species pairs, with general habitat, pollinator, and fire-survival strategy shifts being especially frequent. Contrary to an established idea that shifts in soil type are frequently associated with speciation of Cape taxa, these shifts were relatively rare, occurring in just 17% of species pairs. More cases of sister species divergence are accompanied solely by floral than by vegetative diversification, suggesting an important role for pollinator-driven speciation. In an analysis of two large orchid genera that have radiated in both the Cape and the rest of southern Africa, the frequency of ecological shifts (general habitat, soil type, altitude and flowering time), did not differ between sister species pairs in the Cape region and those outside it. Despite suggestions that Cape plants tend to have small range sizes and show fine-scale patterns of speciation, range size did not differ significantly between species in the Cape and those outside it. We conclude that ecological speciation is likely to have been important for radiation of the Cape flora, but there is no evidence as yet for special "Cape" patterns of ecological speciation.

Virulence strategies in parasitoid Hymenoptera as an example of adaptive diversity

Parasitoids are mostly insects that develop at the expense of other arthropods, which will die as a result of the interaction. Their reproductive success thus totally depends on their ability to successfully infest their host whose reproductive success relies on its own ability to avoid or overcome parasitism. Such intense selective pressures have resulted in extremely diverse adaptations in parasitoid strategies that ensure parasitism success. For instance, wasp-specific viruses (polydnaviruses) are injected into the host by parasitoid females to modulate its physiology and immunity. This article synthesizes available physiological and molecular data on parasitoid virulence strategies and discusses the evolutionary processes at work.

Secretogranin III directs secretory vesicle biogenesis in mast cells in a manner dependent upon interaction with chromogranin A

Mast cells are granular immunocytes that reside in the body's barrier tissues. These cells orchestrate inflammatory responses. Proinflammatory mediators are stored in granular structures within the mast cell cytosol. Control of mast cell granule exocytosis is a major therapeutic goal for allergic and inflammatory diseases. However, the proteins that control granule biogenesis and abundance in mast cells have not been elucidated. In neuroendocrine cells, whose dense core granules are strikingly similar to mast cell granules, granin proteins regulate granulogenesis. Our studies suggest that the Secretogranin III (SgIII) protein is involved in secretory granule biogenesis in mast cells. SgIII is abundant in mast cells, and is organized into vesicular structures. Our results show that over-expression of SgIII in mast cells is sufficient to cause an expansion of a granular compartment in these cells. These novel granules store inflammatory mediators that are released in response to physiological stimuli, indicating that they function as bona fide secretory vesicles. In mast cells, as in neuroendocrine cells, we show that SgIII is complexed with Chromogranin A (CgA). CgA is granulogenic when complexed with SgIII. Our data show that a novel non-granulogenic truncation mutant of SgIII (1-210) lacks the ability to interact with CgA. Thus, in mast cells, a CgA-SgIII complex may play a key role in secretory granule biogenesis. SgIII function in mast cells is unlikely to be limited to its partnership with CgA, as our interaction trap analysis suggests that SgIII has multiple binding partners, including the mast cell ion channel TRPA1.

The mammal assemblage of the hominid site TM266 (Late Miocene, Chad Basin): ecological structure and paleoenvironmental implications

Characterizing the paleoenvironmental context of the first hominids is a key issue for understanding their behavioral and morphological evolution. The present study aims at reconstructing the paleoenvironment of the TM266 vertebrate assemblage (Toros-Menalla, Northern Chad) that yielded the earliest known hominid Sahelanthropus tchadensis (7 Ma). For the first time, a quantitative analysis is carried out on the fossil mammal assemblage associated with that hominid. Two complementary approaches were applied: (1) the analysis of the relative abundances of taxa and their habitat preferences; and (2) the study of the distribution of taxa within three meaningful ecovariables: locomotion, feeding preferences, and body mass. The resulting taxonomic and paleoecological structures are used to reconstruct the diversity and the relative extent of the habitats in that part of northern Chad seven million years ago. The paleoenvironment was composed of open areas with dry and humid grasslands, prevailing over wooded habitats. Water was also widely available as freshwater bodies and certainly swamps. It appears that the high habitat diversity of the landscape is a common feature among paleoenvironments associated with early hominids.

delta-Opioid receptor antagonism induces NMDA receptor-dependent excitotoxicity in anoxic turtle cortex

delta-Opioid receptor (DOR) activation is neuroprotective against short-term anoxic insults in the mammalian brain. This protection may be conferred by inhibition of N-methyl-d-aspartate receptors (NMDARs), whose over-activation during anoxia otherwise leads to a deleterious accumulation of cytosolic calcium ([Ca(2+)](c)), severe membrane potential (E(m)) depolarization and excitotoxic cell death (ECD). Conversely, NMDAR activity is decreased by approximately 50% with anoxia in the cortex of the painted turtle, and large elevations in [Ca(2+)](c), severe E(m) depolarization and ECD are avoided. DORs are expressed in high quantity throughout the turtle brain relative to the mammalian brain; however, the role of DORs in anoxic NMDAR regulation has not been investigated in turtles. We examined the effect of DOR blockade with naltrindole (1-10 micromol l(-1)) on E(m), NMDAR activity and [Ca(2+)](c) homeostasis in turtle cortical neurons during normoxia and the transition to anoxia. Naltrindole potentiated normoxic NMDAR currents by 78+/-5% and increased [Ca(2+)](c) by 13+/-4%. Anoxic neurons treated with naltrindole were strongly depolarized, NMDAR currents were potentiated by 70+/-15%, and [Ca(2+)](c) increased 5-fold compared with anoxic controls. Following naltrindole washout, E(m) remained depolarized and [Ca(2+)](c) became further elevated in all neurons. The naltrindole-mediated depolarization and increased [Ca(2+)](c) were prevented by NMDAR antagonism or by perfusion of the G(i) protein agonist mastoparan-7, which also reversed the naltrindole-mediated potentiation of NMDAR currents. Together, these data suggest that DORs mediate NMDAR activity in a G(i)-dependent manner and prevent deleterious NMDAR-mediated [Ca(2+)](c) influx during anoxic insults in the turtle cortex.

Graphing evolutionary pattern and process: a history of techniques in archaeology and paleobiology

Graphs displaying evolutionary patterns are common in paleontology and in United States archaeology. Both disciplines subscribed to a transformational theory of evolution and graphed evolution as a sequence of archetypes in the late nineteenth and early twentieth centuries. U.S. archaeologists in the second decade of the twentieth century, and paleontologists shortly thereafter, developed distinct graphic styles that reflected the Darwinian variational model of evolution. Paleobiologists adopted the view of a species as a set of phenotypically variant individuals and graphed those variations either as central tendencies or as histograms of frequencies of variants. Archaeologists presumed their artifact types reflected cultural norms of prehistoric artisans and the frequency of specimens in each type reflected human choice and type popularity. They graphed cultural evolution as shifts in frequencies of specimens representing each of several artifact types. Confusion of pattern and process is exemplified by a paleobiologist misinterpreting the process illustrated by an archaeological graph, and an archaeologist misinterpreting the process illustrated by a paleobiological graph. Each style of graph displays particular evolutionary patterns and implies particular evolutionary processes. Graphs of a multistratum collection of prehistoric mammal remains and a multistratum collection of artifacts demonstrate that many graph styles can be used for both kinds of collections.

The earliest stages of ecosystem succession in high-elevation (5000 metres above sea level), recently deglaciated soils

Global climate change has accelerated the pace of glacial retreat in high-latitude and high-elevation environments, exposing lands that remain devoid of vegetation for many years. The exposure of 'new' soil is particularly apparent at high elevations (5000 metres above sea level) in the Peruvian Andes, where extreme environmental conditions hinder plant colonization. Nonetheless, these seemingly barren soils contain a diverse microbial community; yet the biogeochemical role of micro-organisms at these extreme elevations remains unknown. Using biogeochemical and molecular techniques, we investigated the biological community structure and ecosystem functioning of the pre-plant stages of primary succession in soils along a high-Andean chronosequence. We found that recently glaciated soils were colonized by a diverse community of cyanobacteria during the first 4-5 years following glacial retreat. This significant increase in cyanobacterial diversity corresponded with equally dramatic increases in soil stability, heterotrophic microbial biomass, soil enzyme activity and the presence and abundance of photosynthetic and photoprotective pigments. Furthermore, we found that soil nitrogen-fixation rates increased almost two orders of magnitude during the first 4-5 years of succession, many years before the establishment of mosses, lichens or vascular plants. Carbon analyses (pyrolysis-gas chromatography/mass spectroscopy) of soil organic matter suggested that soil carbon along the chronosequence was of microbial origin. This indicates that inputs of nutrients and organic matter during early ecosystem development at these sites are dominated by microbial carbon and nitrogen fixation. Overall, our results indicate that photosynthetic and nitrogen-fixing bacteria play important roles in acquiring nutrients and facilitating ecological succession in soils near some of the highest elevation receding glaciers on the Earth.

Genetic diversity of the endemic gourmet mushroom Thelephora ganbajun from south-western China

The ectomycorrhizal fungus Thelephora ganbajun is an endemic gourmet mushroom in Yunnan province, south-western China. However, despite its widespread consumer appeal, nutritional value and potential ecological role in natural forests, very little is known about its genetics, diversity and ecology. In this study, we investigated DNA sequence variation at the internal transcribed spacer (ITS) regions among 156 specimens collected from 23 sites of nine regions in Yunnan Province. Our analysis identified a total of 34 ITS haplotypes and these haplotypes were clustered into five distinct phylogenetic groups. The evolutionary divergences among these clades are similar to or greater than many known sister species pairs within the genus Thelephora and the closely related genus Tomentella. Among the 34 ITS haplotypes, 22 were represented by one specimen each and the remaining 12 were each shared by two or more specimens. The most common haplotype contained 68 specimens distributed in 21 of the 23 sites, a result consistent with gene flow among geographical populations. However, analysis of molecular variance (AMOVA) revealed low but significant genetic differentiation among local and regional populations. Interestingly, the Mantel test identified that the extent of genetic differentiation was not significantly correlated with geographical distance. Our study revealed significant genetic divergence within Th. ganbajun and limited but detectable gene flow among geographical populations of this endemic ectomycorrhizal gourmet mushroom.

Elicitor-induced transcription factors for metabolic reprogramming of secondary metabolism in Medicago truncatula

BACKGROUND

Exposure of Medicago truncatula cell suspension cultures to pathogen or wound signals leads to accumulation of various classes of flavonoid and/or triterpene defense molecules, orchestrated via a complex signalling network in which transcription factors (TFs) are essential components.

RESULTS

In this study, we analyzed TFs responding to yeast elicitor (YE) or methyl jasmonate (MJ). From 502 differentially expressed TFs, WRKY and AP2/EREBP gene families were over-represented among YE-induced genes whereas Basic Helix-Loop-Helix (bHLH) family members were more over-represented among the MJ-induced genes. Jasmonate ZIM-domain (JAZ) transcriptional regulators were highly induced by MJ treatment. To investigate potential involvement of WRKY TFs in signalling, we expressed four Medicago WRKY genes in tobacco. Levels of soluble and wall bound phenolic compounds and lignin were increased in all cases. WRKY W109669 also induced tobacco endo-1,3-beta-glucanase (NtPR2) and enhanced the systemic defense response to tobacco mosaic virus in transgenic tobacco plants.

CONCLUSION

These results confirm that Medicago WRKY TFs have broad roles in orchestrating metabolic responses to biotic stress, and that they also represent potentially valuable reagents for engineering metabolic changes that impact pathogen resistance.

Fossil evidence for the origin of spider spinnerets, and a proposed arachnid order

Silk production from opisthosomal glands is a defining characteristic of spiders (Araneae). Silk emerges from spigots (modified setae) borne on spinnerets (modified appendages). Spigots from Attercopus fimbriunguis, from Middle Devonian (386 Ma) strata of Gilboa, New York, were described in 1989 as evidence for the oldest spider and the first use of silk by animals. Slightly younger (374 Ma) material from South Mountain, New York, conspecific with A. fimbriunguis, includes spigots and other evidence that elucidate the evolution of early Araneae and the origin of spider silk. No known Attercopus spigots, including the original specimen, occur on true spinnerets but are arranged along the edges of plates. Spinnerets originated from biramous appendages of opisthosomal somites 4 and 5; although present in Limulus, no other arachnids have opisthosomal appendage homologues on these segments. The spigot arrangement in Attercopus shows a primitive state before the reexpression of the dormant genetic mechanism that gave rise to spinnerets in later spiders. Enigmatic flagellar structures originally described as Arachnida incertae sedis, are shown to be Attercopus anal flagella, as found in Permarachne, also originally described as a spider. An arachnid order, Uraraneida, is erected for a plesion, including these two genera, based on this combination of characters. The inability of Uraraneida precisely to control silk weaving suggests its original use as a wrapping, lining, or homing material.

Social personality trait and fitness

Several recent studies have explored various aspects of animal personality and their ecological consequences. However, the processes responsible for the maintenance of personality variability within a population are still largely unknown. We have recently demonstrated that social personality traits exist in the common lizard (Lacerta vivipara) and that the variation in sociability provides an explanation for variable dispersal responses within a given species. However, we need to know the fitness consequences of variation in sociability across environmental contexts in order to better understand the maintenance of such variation. In order to achieve this, we investigated the relationship between sociability and survival, body growth and fecundity, in one-year-old individuals in semi-natural populations with varying density. 'Asocial' and 'social' lizards displayed different fitness outcomes in populations of different densities. Asocial lizards survived better in low-density populations, while social females reproduced better. Spatiotemporal variation in environmental conditions might thus be the process underlying the maintenance of these personality traits within a population. Finally, we also discuss the position of sociability in a more general individual behavioural pattern including boldness, exploration and aggressiveness.

Sexually antagonistic "zygotic drive" of the sex chromosomes

Genomic conflict is perplexing because it causes the fitness of a species to decline rather than improve. Many diverse forms of genomic conflict have been identified, but this extant tally may be incomplete. Here, we show that the unusual characteristics of the sex chromosomes can, in principle, lead to a previously unappreciated form of sexual genomic conflict. The phenomenon occurs because there is selection in the heterogametic sex for sex-linked mutations that harm the sex of offspring that does not carry them, whenever there is competition among siblings. This harmful phenotype can be expressed as an antagonistic green-beard effect that is mediated by epigenetic parental effects, parental investment, and/or interactions among siblings. We call this form of genomic conflict sexually antagonistic “zygotic drive”, because it is functionally equivalent to meiotic drive, except that it operates during the zygotic and postzygotic stages of the life cycle rather than the meiotic and gametic stages. A combination of mathematical modeling and a survey of empirical studies is used to show that sexually antagonistic zygotic drive is feasible, likely to be widespread in nature, and that it can promote a genetic “arms race” between the homo- and heteromorphic sex chromosomes. This new category of genomic conflict has the potential to strongly influence other fundamental evolutionary processes, such as speciation and the degeneration of the Y and W sex chromosomes. It also fosters a new genetic hypothesis for the evolution of enigmatic fitness-reducing traits like the high frequency of spontaneous abortion, sterility, and homosexuality observed in humans.

Our study describes a new form of sexual genomic conflict that operates through the process of antagonistic green-beard effects. Although past theoretical and empirical work indicated that green-beard effects rarely operate in nature, our new theory shows why this conclusion may have to be reevaluated. We integrate modeling analysis with extant empirical work to show that the unique properties of sex chromosomes can lead to a previously unappreciated form of sexual conflict (sexually antagonistic zygotic drive) that may be widespread in nature. It operates through harmful epigenetic parental effects, asymmetrical allocation of parental investment to sons and daughters, and asymmetrical interactions between brothers and sisters. Sexually antagonistic zygotic drive is functionally analogous to meiotic drive except that it operates due to competition among opposite-sex siblings rather than between competing gametes.

Chloride Is essential for capacitation and for the capacitation-associated increase in tyrosine phosphorylation

After epididymal maturation, sperm capacitation, which encompasses a complex series of molecular events, endows the sperm with the ability to fertilize an egg. This process can be mimicked in vitro in defined media, the composition of which is based on the electrolyte concentration of the oviductal fluid. It is well established that capacitation requires Na(+), HCO(3)(-), Ca(2+), and a cholesterol acceptor; however, little is known about the function of Cl(-) during this important process. To determine whether Cl(-), in addition to maintaining osmolarity, actively participates in signaling pathways that regulate capacitation, Cl(-) was replaced by either methanesulfonate or gluconate two nonpermeable anions. The absence of Cl(-) did not affect sperm viability, but capacitation-associated processes such as the increase in tyrosine phosphorylation, the increase in cAMP levels, hyperactivation, the zona pellucidae-induced acrosome reaction, and most importantly, fertilization were abolished or significantly reduced. Interestingly, the addition of cyclic AMP agonists to sperm incubated in Cl(-)-free medium rescued the increase in tyrosine phosphorylation and hyperactivation suggesting that Cl(-) acts upstream of the cAMP/protein kinase A signaling pathway. To investigate Cl(-) transport, sperm incubated in complete capacitation medium were exposed to a battery of anion transport inhibitors. Among them, bumetanide and furosemide, two blockers of Na(+)/K(+)/Cl(-) cotransporters (NKCC), inhibited all capacitation-associated events, suggesting that these transporters may mediate Cl(-) movements in sperm. Consistent with these results, Western blots using anti-NKCC1 antibodies showed the presence of this cotransporter in mature sperm.

Visual ecology of the Australian lungfish (Neoceratodus forsteri)

Background

The transition from water to land was a key event in the evolution of vertebrates that occurred over a period of 15–20 million years towards the end of the Devonian. Tetrapods, including all land-living vertebrates, are thought to have evolved from lobe-finned (sarcopterygian) fish that developed adaptations for an amphibious existence. However, while many of the biomechanical and physiological modifications necessary to achieve this feat have been studied in detail, little is known about the sensory adaptations accompanying this transition. In this study, we investigated the visual system and visual ecology of the Australian lungfish Neoceratodus forsteri, which is the most primitive of all the lungfish and possibly the closest living relative to the ancestors of tetrapods.

Results

Juvenile Neoceratodus have five spectrally distinct retinal visual pigments. A single type of rod photoreceptor contains a visual pigment with a wavelength of maximum absorbance (λ_max) at 540 nm. Four spectrally distinct single cone photoreceptors contain visual pigments with λ_max at 366 (UVS), 479 (SWS), 558 (MWS) and 623 nm (LWS). No double cones were found. Adult lungfish do not possess UVS cones and, unlike juveniles, have ocular media that prevent ultraviolet light from reaching the retina. Yellow ellipsoidal/paraboloidal pigments in the MWS cones and red oil droplets in the LWS cones narrow the spectral sensitivity functions of these photoreceptors and shift their peak sensitivity to 584 nm and 656 nm, respectively. Modelling of the effects of these intracellular spectral filters on the photoreceptor colour space of Neoceratodus suggests that they enhance their ability to discriminate objects, such as plants and other lungfishes, on the basis of colour.

Conclusion

The presence of a complex colour vision system based on multiple cone types and intracellular spectral filters in lungfishes suggests that many of the ocular characteristics seen in terrestrial or secondarily aquatic vertebrates, such as birds and turtles, may have evolved in shallow water prior to the transition onto land. Moreover, the benefits of spectral filters for colour discrimination apply equally to purely aquatic species as well as semi-aquatic and terrestrial animals. The visual system of the Australian lungfish resembles that of terrestrial vertebrates far more closely than that of other sarcopterygian fish. This supports the idea that lungfishes, and not the coelacanth, are the closest living relatives of the ancestors of tetrapods.

Fishery-induced selection on an Alpine whitefish: quantifying genetic and environmental effects on individual growth rate

Size-selective fishing, environmental changes and reproductive strategies are expected to affect life-history traits such as the individual growth rate. The relative contribution of these factors is not clear, particularly whether size-selective fishing can have a substantial impact on the genetics and hence on the evolution of individual growth rates in wild populations. We analysed a 25-year monitoring survey of an isolated population of the Alpine whitefish Coregonus palaea. We determined the selection differentials on growth rate, the actual change of growth rate over time and indicators of reproductive strategies that may potentially change over time. The selection differential can be reliably estimated in our study population because almost all the fish are harvested within their first years of life, i.e. few fish escape fishing mortality. We found a marked decline in average adult growth rate over the 25 years and a significant selection differential for adult growth, but no evidence for any linear change in reproductive strategies over time. Assuming that the heritability of growth in this whitefish corresponds to what was found in other salmonids, about a third of the observed decline in growth rate would be linked to fishery-induced evolution. Size-selective fishing seems to affect substantially the genetics of individual growth in our study population.

Ethanol exposure induces differential microRNA and target gene expression and teratogenic effects which can be suppressed by folic acid supplementation

BACKGROUND

microRNAs (miRNAs) play an important role in development and are associated with birth defects. Data are scant on the role of miRNAs in birth defects arising from exposure to environmental factors such as alcohol.

METHODS

In this study, we determined the expression levels of 509 mature miRNAs in fetal mouse brains with or without prenatal ethanol exposure using a miRNA microarray technique, verified by northern blot and PCR. Mouse embryos in culture were used to examine the effect of ethanol treatment on expression of the putative target genes of miR-10a (Hoxa1 and other Hox members) at mRNA and protein level. Open field and Morris water maze tests were also performed at post-natal day 35.

RESULTS

Ethanol treatment induced major fetal teratogenesis in mice and caused mental retardation in their offspring, namely lower locomotor activity (P < 0.01) and impaired task acquisition. Of the screened miRNAs, miR-10a, miR-10b, miR-9, miR-145, miR-30a-3p and miR-152 were up-regulated (fold change >1.5) in fetal brains with prenatal ethanol exposure, whereas miR-200a, miR-496, miR-296, miR-30e-5p, miR-362, miR-339, miR-29c and miR-154 were down-regulated (fold change <0.67). Both miR-10a and miR-10b were significantly up-regulated (P < 0.01) in brain after prenatal ethanol exposure. Ethanol treatment also caused major obstruction in the development of cultured embryos, with down-regulated Hoxa1. Co-incubation with folic acid blocked ethanol-induced teratogenesis, with up-regulated Hoxa1 and down-regulated miR-10a (P < 0.01).

CONCLUSIONS

The study provided new insights into the role of miRNAs and their target genes in the pathogenesis of fetal alcohol syndrome.

Temperature downshift induces antioxidant response in fungi isolated from Antarctica

Although investigators have been studying the cold-shock response in a variety of organisms for the last two decades or more, comparatively little is known about the difference between antioxidant cell response to cold stress in Antarctic and temperate microorganisms. The change of environmental temperature, which is one of the most common stresses, could be crucial for their use in the biotechnological industry and in ecological research. We compared the effect of short-term temperature downshift on antioxidant cell response in Antarctic and temperate fungi belonging to the genus Penicillium. Our study showed that downshift from an optimal temperature to 15 degrees or 6 degrees C led to a cell response typical of oxidative stress: significant reduction of biomass production; increase in the levels of oxidative damaged proteins and accumulation of storage carbohydrates (glycogen and trehalose) in comparison to growth at optimal temperature. Cell response against cold stress includes also increase in the activities of SOD and CAT, which are key enzymes for directly scavenging reactive oxygen species. This response is more species-dependent than dependent on the degree of cold-shock. Antarctic psychrotolerant strain Penicillium olsonii p14 that is adapted to life in extremely cold conditions demonstrated enhanced tolerance to temperature downshift in comparison with both mesophilic strains (Antarctic Penicillium waksmanii m12 and temperate Penicillium sp. t35).

New insights into the evolution of intronic sequences of the beta-fibrinogen gene and their application in reconstructing mustelid phylogeny

Mustelidae is the largest and most diverse family in the order Carnivora. The phylogenetic relationships among the subfamilies have especially long been a focus of study. Herein we are among the first to employ two new introns (4 and 7) of the nuclear beta-fibrinogen gene to clarify these enigmatic problems. In addition, two previously available nuclear (IRBP exon 1 and TTR intron 1) and one mt (ND2) data sets were also combined and analyzed simultaneously with the newly obtained sequence data in this study. Detailed characterizations of the two intronic regions not only reveal the remarkable occurrences of short interspersed element (SINE) insertion events, providing a new example supporting the attractive hypothesis that attrition of an earlier retroposition may offer a proper environment for successive retropositions by forming a "dimer-like" structure, but also demonstrate their utility in the resolution of mustelid phylogeny. All of our analyses confirm the assemblage of Mustelinae, Lutrinae, and Melinae with confidence; moreover, two clades within Mustelinae were clearly recognized, i.e., genera Mustela and Martes. Notably, genus Martes of Mustelinae was found to branch off first, followed by Melinae and then a clade containing Lutrinae and genus Mustela of Mustelinae, indicating paraphyly of Mustelinae. In addition, Mephitinae diverges before the other mustelids and the monophyletic Procyonidae in all cases, supporting its elevation to a separate family. Additional independent genetic markers are still in need to resolve the trichotomy among Mephitinae and the other two carnivoran clades, Ailuridae and Procyonidae/non-mephitine Mustelidae.