Selection drives convergent gene expression changes during transitions to co-sexuality in haploid sexual systems.

Co-sexuality has evolved repeatedly from unisexual (dioicous) ancestors across a wide range of taxa. However, the molecular changes underpinning this important transition remain unknown, particularly in organisms with haploid sexual systems such as bryophytes, red algae and brown algae. Here we explore four independent events of emergence of co-sexuality from unisexual ancestors in brown algal clades to examine the nature, evolution and degree of convergence of gene expression changes that accompany the breakdown of dioicy. The amounts of male versus female phenotypic differences in dioicous species were not correlated with the extent of sex-biased gene expression, in stark contrast to what is observed in animals. Although sex-biased genes exhibited a high turnover rate during brown alga diversification, some of their predicted functions were conserved across species. Transitions to co-sexuality consistently involved adaptive gene expression shifts and rapid sequence evolution, particularly for male-biased genes. Gene expression in co-sexual species was more similar to that in females rather than males of related dioicous species, suggesting that co-sexuality may have arisen from ancestral females. Finally, extensive convergent gene expression changes, driven by selection, were associated with the transition to co-sexuality. Together, our observations provide insights on how co-sexual systems arise from ancestral, haploid UV sexual systems.

The rapid dissolution of dioecy by experimental evolution.

Evolutionary transitions from hermaphroditism to dioecy have been common in flowering plants,1,2 but recent analysis also points to frequent reversions from dioecy to hermaphroditism.2-4 Here, we use experimental evolution to expose a mechanism for such reversions, validating an explanation for the scattered phylogenetic distribution of dioecy. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that occasionally produced male flowers; such "leaky" sex expression is common in both males and females of dioecious plants.5 Over the course of four generations, females evolved a 23-fold increase in average male flower production. This phenotypic masculinization of females coincided with the evolution of partial self-fertilization, high average seed set in the continued absence of males, and a capacity to sire progeny when males were re-introduced into their populations. Our study thus validates a mechanism for the rapid dissolution of dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion.6,7 Our results illustrate the power of natural selection, acting in replicated experimental populations, to bring about transitions in the mating behavior of plants.

Enhanced leaky sex expression in response to pollen limitation in the dioecious plant Mercurialis annua.

In dioecious plants, males and females frequently show 'leaky' sex expression, with individuals occasionally producing flowers of the opposite sex. This leaky sex expression may have enabled the colonization of oceanic islands by dioecious plant species, and it is likely to represent the sort of variation upon which selection acts to bring about evolutionary transitions from dioecy to hermaphroditism. Although leakiness is commonly reported for dioecious species, it is not known whether it has plastic component. The question is interesting because males or females with an ability to enhance their leakiness plastically in the absence of mates would have an advantage of being able to produce progeny by self-fertilization. Here, we demonstrate that leaky sex expression in the wind-pollinated dioecious herb Mercurialis annua is plastically responsive to its mating context. We compared experimental populations of females growing either with or without males. Females growing in the absence of males were leakier in their sex expression than controls growing with males, producing more than twice as many male flowers. Our results thus provide a striking instance of plasticity in the reproductive behaviour of plants that is likely adaptive. We consider how females might sense their mating environment as a function of pollen availability, and we discuss possible constraints on the evolution of plasticity in sex expression when the environmental signals that individuals receive are unreliable.

YY males of the dioecious plant Mercurialis annua are fully viable but produce largely infertile pollen.

The suppression of recombination during sex-chromosome evolution is thought to be favoured by linkage between the sex-determining locus and sexually antagonistic loci, and leads to the degeneration of the chromosome restricted to the heterogametic sex. Despite substantial evidence for genetic degeneration at the sequence level, the phenotypic effects of the earliest stages of sex-chromosome evolution are poorly known. Here, we compare the morphology, viability and fertility between XY and YY individuals produced by crossing seed-producing males in the dioecious plant Mercurialis annua, which has young sex chromosomes with limited X-Y sequence divergence. We found no significant difference in viability or vegetative morphology between XY and YY males. However, electron microscopy revealed clear differences in pollen anatomy, and YY males were significantly poorer sires in competition with their XY counterparts. Our study suggests either that the X chromosome is required for full male fertility in M. annua, or that male fertility is sensitive to the dosage of relevant Y-linked genes. We discuss the possibility that the maintenance of male-fertility genes on the X chromosome might have been favoured in recent population expansions that selected for the ability of females to produce pollen in the absence of males.

A functional decomposition of sex inconstancy in the dioecious, colonizing plant Mercurialis annua.

PREMISE: Plants with separate sexes often show "inconstant" or "leaky" sex expression, with females or males producing a few flowers of the opposite sex. The frequency and degree of such inconstancy may reflect residual hermaphroditic sex allocation after an evolutionary transition from combined to separate sexes. Sex inconstancy also represents a possible first step in the breakdown of dioecy back to hermaphroditism. In the Mercurialis annua (Euphorbiaceae) species complex, monoecy and androdioecy have evolved from dioecy in polyploid populations. Here, we characterize patterns of sex inconstancy in dioecious M. annua and discuss how sex inconstancy may have contributed to the breakdown of separate sexes in the genus. METHODS: We measured sex inconstancy in three common gardens of M. annua over 2 years using a modification of Lloyd's phenotypic gender in terms of frequency and degree, with the degree calibrating inconstancy against the sex allocation of constant males and constant females, yielding a measure of gender that does not depend on the distribution of gender in the population. RESULTS: Unusually for dioecious plants, the frequency of sex inconstancy in M. annua was greater in females, but its degree was greater for males in the 2 years of study. We suggest that this pattern is consistent with the maintenance of inconstancy in dioecious M. annua by selection for reproductive assurance under mate limitation. CONCLUSIONS: Our study illustrates the utility of decomposing measures of sex inconstancy into its frequency and its degree and throws new light on the origin of variation in sexual systems in Mercurialis.

Sexual dimorphism and rapid turnover in gene expression in pre-reproductive seedlings of a dioecious herb.

BACKGROUND AND AIMS: Sexual dimorphism in morphology, physiology or life history traits is common in dioecious plants at reproductive maturity, but it is typically inconspicuous or absent in juveniles. Although plants of different sexes probably begin to diverge in gene expression both before their reproduction commences and before dimorphism becomes readily apparent, to our knowledge transcriptome-wide differential gene expression has yet to be demonstrated for any angiosperm species. METHODS: The present study documents differences in gene expression in both above- and below-ground tissues of early pre-reproductive individuals of the wind-pollinated dioecious annual herb, Mercurialis annua, which otherwise shows clear sexual dimorphism only at the adult stage. KEY RESULTS: Whereas males and females differed in their gene expression at the first leaf stage, sex-biased gene expression peaked just prior to, and after, flowering, as might be expected if sexual dimorphism is partly a response to differential costs of reproduction. Sex-biased genes were over-represented among putative sex-linked genes in M. annua but showed no evidence for more rapid evolution than unbiased genes. CONCLUSIONS: Sex-biased gene expression in M. annua occurs as early as the first whorl of leaves is produced, is highly dynamic during plant development and varies substantially between vegetative tissues.

Poly(oligo(ethylene glycol) vinyl acetate)s: A Versatile Class of Thermoresponsive and Biocompatible Polymers.

Polymers with a thermally triggered phase transition are important in the design of materials for biological applications, where their behavior can be used to trigger release or (dis)assembly events. Despite their advantages, a system with tunable thermal response, end-group reactive sites, low toxicity, and controlled main-chain degradability has not been realized, yet this would be a significant advance. The versatile new poly(oligo(ethylene glycol) vinyl acetate)s are presented with excellent control over their molecular properties obtained through RAFT/MADIX polymerization. Furthermore, we demonstrate structure-controlled thermal transitions, conjugation to human lysozyme through the retained end-group, and moreover show that this class of polymers can uniquely be copolymerized with 2-methylene-1,3-dioxepane (MDO) to generate polymers in which the degradability and cloud point can be independently tuned to create materials that display the same cloud point but degrade differently.

Failure of combination therapy for Staphylococcus aureus bone infection: a case of in vivo selection with resistance to rifampicin and fusidic acid.

Staphylococcus aureus is one of the main etiologies of bone and device-related infections. Treatment of these orthopedic infections combines mostly rifampicin with other antibiotics. The recurrence or failure rate after fusidic acid/rifampicin treatment remains low (<10%). We discuss here a case of antibiotic treatment failure for Staphylococcus aureus bone infection with in vivo selection of rifampicin and fusidic acid resistance. We also report a new mutation in fusA gene involved in fusidic acid resistance.

Medical and pharmacy student concerns about participating on international service-learning trips.

BACKGROUND: International Service Learning Trips (ISLT) provide health professional students the opportunity to provide healthcare, under the direction of trained faculty, to underserved populations in developing countries. Despite recent increases in international service learning trips, there is scant literature addressing concerns students have prior to attending such trips. This study focuses on identifying concerns before and after attending an ISLT and their impact on students. METHODS: A survey comprised of closed and open-ended questions was developed to elucidate student concerns prior to attending an ISLT and experiences which might influence concerns. A five-point Likert-scale (extremely concerned = 1, minimally concerned = 5) was used to rate apprehension and satisfaction. Paired t-test was used to compare pre- and post-trip concerns; Chi-Square test was used to compare groups. RESULTS: Thirty-five students (27 medical, 8 pharmacy) attended ISLTs in December 2013. All completed pre and post-trip surveys. Significant decreases were seen in concerns related to cultural barriers (4.14 vs 4.46, P = .047), disease/epidemics (3.34 vs 4.60, P < .001), natural disasters (3.94 vs 4.94, P < .001), terrorism (4.34 vs 4.94, P < .001), travel (3.86 vs 4.51, P < .001) monetary issues (3.80 vs 4.60, P < .001), hospitality (3.94 vs 4.74, P = .001) and food (3.83 vs 4.60, P < .001). Language and group dynamics remained concerns post-trip. On open-ended questions, students described benefits of attending an ISLT. CONCLUSIONS: Students had multiple concerns prior to attending an ISLT. Most decreased upon return. Addressing concerns has the potential to decrease student apprehension. The results of this study highlight the benefits of providing ISLTs and supporting development of a curriculum incorporating trip-related concerns.

Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods.

Epidemiological study on chronic venous disease in Belgium and Luxembourg: prevalence, risk factors, and symptomatology.

OBJECTIVE: This epidemiological study measured the prevalence of chronic venous disease (CVD) in Belgium and Luxembourg. Possible risk factors and the symptomatology were evaluated. MATERIAL AND METHODS: A survey was carried out in Belgium and Luxembourg between May and September 2013. Patient recruitment was carried out by 406 general practitioners (GPs). Each GP screened 10-20 consecutive patients older than 18 years, and in total 6009 patients were included. Patient characteristics, prevalence of risk factors, symptomatology, and C-classification were noted. The GPs diagnosed CVD and measured the need for treatment. Patients with diagnosed CVD completed a questionnaire about their history of leg problems and a quality of life score (CIVIQ-14). These data were converted into a CIVIQ Global Index Score (GIS). RESULTS: The mean age of the patients was 53.4 years, and they were predominantly female (67.5%). Among the 3889 symptomatic patients, heavy legs, pain, and sensation of leg swelling were the most common complaints. Among the included patients, 61.3% of patients were classified within C1-C6; however, only 45.9% of these patients were considered by the GPs to be suffering CVD. Treatment was offered to 49.5% of patients. Age and female gender correlate with a higher C-class (p < .001). Patients with a higher C-class (C3-C6) have significantly more pain, sensation of swelling and burning, night cramps, itching, and the sensation of "pins and needles" in the legs. Patients taking regular exercise and without a family history had a lower C-class. Higher BMI, age, female gender, family history, history of thrombophlebitis, and a higher C-class correlated with a lower GIS (p < .001). Of the patients with CVD, 10.4% had lost days of work because of their venous leg problems. CONCLUSION: CVD is a very common disease, which is underestimated. The prevalence increases with age, generates incapacity to work, and worsens the patients' quality of life.

Numerical study of the impact of vegetation coverings on sound levels and time decays in a canyon street model.

Given a constantly increasing urban population, the mitigation of environmental impacts caused by urbanization has become a critical concern. Sprawling cities accelerate the phenomenon of soil sealing, whose impacts relative to climatology, water cycle and ecology are substantial. The "VegDUD" project, which provides the framework for the present paper, lays out a possible alternative for limiting these deleterious effects through focusing on the role of vegetation in promoting sustainable urban development. The study presented herein addresses the beneficial effect of greening building facades and rooftops in terms of both acoustic level and sound-decay time indicators at low frequency third-octave bands. This is carried out through numerical simulations in the time-domain of sound propagation in a canyon street of infinite length for various scenarios of surface vegetalization. Numerical predictions show a more significant effect in the upper part and outside the street, depending on the location of the vegetalized surfaces, frequency bands and number of reflections on the treated materials.

Methicillin-susceptible Staphylococcus aureus CC398: first description in prosthetic joint infection and genetic background comparison with nasal carriage isolates.

Few reports described infections with CC398 methicillin-susceptible Staphylococcus aureus (MSSA). We compared the genetic background of CC398 MSSA strains from nasal carriage and knee arthroplasty infection. DNA microarray analysis shows acquisition of particular adhesin, iron capture system and immune defense evasion mechanisms. These characteristics could explain pathogenesis in this type of infection.

A new anaplerotic respiratory pathway involving lysine biosynthesis in isocitrate dehydrogenase-deficient Arabidopsis mutants.

The cornerstone of carbon (C) and nitrogen (N) metabolic interactions - respiration - is presently not well understood in plant cells: the source of the key intermediate 2-oxoglutarate (2OG), to which reduced N is combined to yield glutamate and glutamine, remains somewhat unclear. We took advantage of combined mutations of NAD- and NADP-dependent isocitrate dehydrogenase activity and investigated the associated metabolic effects in Arabidopsis leaves (the major site of N assimilation in this genus), using metabolomics and (13)C-labelling techniques. We show that a substantial reduction in leaf isocitrate dehydrogenase activity did not lead to changes in the respiration efflux rate but respiratory metabolism was reorchestrated: 2OG production was supplemented by a metabolic bypass involving both lysine synthesis and degradation. Although the recycling of lysine has long been considered important in sustaining respiration, we show here that lysine neosynthesis itself participates in an alternative respiratory pathway. Lys metabolism thus contributes to explaining the metabolic flexibility of plant leaves and the effect (or the lack thereof) of respiratory mutations.

Gene transfer from bacteria and archaea facilitated evolution of an extremophilic eukaryote.

Some microbial eukaryotes, such as the extremophilic red alga Galdieria sulphuraria, live in hot, toxic metal-rich, acidic environments. To elucidate the underlying molecular mechanisms of adaptation, we sequenced the 13.7-megabase genome of G. sulphuraria. This alga shows an enormous metabolic flexibility, growing either photoautotrophically or heterotrophically on more than 50 carbon sources. Environmental adaptation seems to have been facilitated by horizontal gene transfer from various bacteria and archaea, often followed by gene family expansion. At least 5% of protein-coding genes of G. sulphuraria were probably acquired horizontally. These proteins are involved in ecologically important processes ranging from heavy-metal detoxification to glycerol uptake and metabolism. Thus, our findings show that a pan-domain gene pool has facilitated environmental adaptation in this unicellular eukaryote.

D2O solvent isotope effects suggest uniform energy barriers in ribulose-1,5-bisphosphate carboxylase/oxygenase catalysis.

d-Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the most abundant enzyme on Earth and is responsible for the fixation of atmospheric CO(2) into biomass. The reaction consists of incorporation of CO(2) and solvent H(2)O into d-ribulose 1,5-bisphosphate (RuBP) to yield 3-phospho-d-glycerate. The reaction involves several proton-dependent events: abstraction and protonation during enolization of RuBP and hydrolysis and reprotonation of the six-carbon reaction intermediate (carboxyketone). Although much is known about Rubisco structure and diversity, fundamental aspects of the reaction mechanism are poorly documented. How and when are protons exchanged among substrate, amino acid residues, and solvent water, and could alterations of proton exchange influence catalytic turnover? What is the energy profile of the reaction? To answer these questions, we measured catalytic rates and the (12)CO(2)/(13)CO(2) isotope effect in isotopic waters. We show that with increasing D(2)O content, the maximal carboxylation velocity (k(cat)(c)) decreased linearly and was 1.7 times lower in pure D(2)O. By contrast, the isotope effect on the apparent Michaelis constant for CO(2) (K(c)) was unity, suggesting that H/D exchange might have occurred with the solvent in early steps thereby slowing the overall catalysis. Calculations of kinetic commitments from observed isotope effects further indicate that (1) enolization and processing of the carboxyketone are similarly rate-limiting and (2) the tendency of the carboxyketone to go backward (decarboxylation) is likely exacerbated upon deuteration. Our results thus suggest that Rubisco catalysis is achieved by a rather equal distribution of energy barriers along the reaction.