Extreme genetic diversity in asexual grass thrips populations.

The continuous generation of genetic variation has been proposed as one of the main factors explaining the maintenance of sexual reproduction in nature. However, populations of asexual individuals may attain high levels of genetic diversity through within-lineage diversification, replicate transitions to asexuality from sexual ancestors and migration. How these mechanisms affect genetic variation in populations of closely related sexual and asexual taxa can therefore provide insights into the role of genetic diversity for the maintenance of sexual reproduction. Here, we evaluate patterns of intra- and interpopulation genetic diversity in sexual and asexual populations of Aptinothrips rufus grass thrips. Asexual A. rufus populations are found throughout the world, whereas sexual populations appear to be confined to few locations in the Mediterranean region. We found that asexual A. rufus populations are characterized by extremely high levels of genetic diversity, both in comparison with their sexual relatives and in comparison with other asexual species. Migration is extensive among asexual populations over large geographic distances, whereas close sexual populations are strongly isolated from each other. The combination of extensive migration with replicate evolution of asexual lineages, and a past demographic expansion in at least one of them, generated high local clone diversities in A. rufus. These high clone diversities in asexual populations may mimic certain benefits conferred by sex via genetic diversity and could help explain the extreme success of asexual A. rufus populations.

Co-evolutionary dynamics between public good producers and cheats in the bacterium Pseudomonas aeruginosa.

The production of beneficial public goods is common in the microbial world, and so is cheating--the exploitation of public goods by nonproducing mutants. Here, we examine co-evolutionary dynamics between cooperators and cheats and ask whether cooperators can evolve strategies to reduce the burden of exploitation, and whether cheats in turn can improve their exploitation abilities. We evolved cooperators of the bacterium Pseudomonas aeruginosa, producing the shareable iron-scavenging siderophore pyoverdine, together with cheats, defective in pyoverdine production but proficient in uptake. We found that cooperators managed to co-exist with cheats in 56% of all replicates over approximately 150 generations of experimental evolution. Growth and competition assays revealed that co-existence was fostered by a combination of general adaptions to the media and specific adaptions to the co-evolving opponent. Phenotypic screening and whole-genome resequencing of evolved clones confirmed this pattern, and suggest that cooperators became less exploitable by cheats because they significantly reduced their pyoverdine investment. Cheats, meanwhile, improved exploitation efficiency through mutations blocking the costly pyoverdine-signalling pathway. Moreover, cooperators and cheats evolved reduced motility, a pattern that likely represents adaptation to laboratory conditions, but at the same time also affects social interactions by reducing strain mixing and pyoverdine sharing. Overall, we observed parallel evolution, where co-existence of cooperators and cheats was enabled by a combination of adaptations to the abiotic and social environment and their interactions.

Evolutionary dynamics of interlinked public goods traits: an experimental study of siderophore production in Pseudomonas aeruginosa.

Public goods cooperation is common in microbes, and there is much interest in understanding how such traits evolve. Research in recent years has identified several important factors that shape the evolutionary dynamics of such systems, yet few studies have investigated scenarios involving interactions between multiple public goods. Here, we offer general predictions about the evolutionary trajectories of two public goods traits having positive, negative or neutral regulatory influence on one another's expression, and we report on a test of some of our predictions in the context of Pseudomonas aeruginosa's production of two interlinked iron-scavenging siderophores. First, we confirmed that both pyoverdine and pyochelin siderophores do operate as public goods under appropriate environmental conditions. We then tracked their production in lines experimentally evolved under different iron-limitation regimes known to favour different siderophore expression profiles. Under strong iron limitation, where pyoverdine represses pyochelin, we saw a decline in pyoverdine and a concomitant increase in pyochelin - consistent with expansion of pyoverdine-defective cheats derepressed for pyochelin. Under moderate iron limitation, pyochelin declined - again consistent with an expected cheat invasion scenario - but there was no concomitant shift in pyoverdine because cross-suppression between the traits is unidirectional only. Alternating exposure to strong and moderate iron limitation caused qualitatively similar though lesser shifts compared to the constant-environment regimes. Our results confirm that the regulatory interconnections between public goods traits can significantly modulate the course of evolution, yet also suggest how we can start to predict the impacts such complexities will have on phenotypic divergence and community stability.

Altered monocyte calcium-sensing receptor expression in patients with type 2 diabetes mellitus and atherosclerosis.

UNLABELLED: The increased cardiovascular risk in type 2 diabetes mellitus (DM2) is the result of disorders of the immune system, including the enhanced reactivity of monocytes and impaired secretion of inflammatory cytokines. The aim of this study was to analyze the expression of calcium-sensing receptor (CaR) in peripheral blood monocytes of individuals with DM2 and peripheral artery disease (PAD). The study included 88 individuals, among them 37 patients with PAD (group A--atherosclerosis), 27 individuals with DM2 and PAD (group AD--atherosclerosis and diabetes mellitus), and 24 controls (group C--controls). The expression of CaR on isolated peripheral blood monocytes was analyzed at the level of surface protein (CaR(surf)) and mRNA (CaR(mRNA)). Concentrations of pro-inflammatory cytokines were determined by means of ELISA, while the severity of PAD was assessed with Doppler and impedance plethysmography. The expression of CaR(surf) was the highest in the controls (mean 41.27%) and did not differ significantly as compared to individuals from group AD (35.66%); however it was significantly higher than in group A (24.49%). The expression of CaR(surf) was related to the severity of PAD, fasting concentration of glucose, and the concentration of monocyte chemotactic protein (MCP-1). Additionally, significant differences were observed with regards to CaR(mRNA) expression; although, no significant relationships were documented between CaR(mRNA) and laboratory or clinical variables. Different ways of CaR(surf) and CaR(mRNA) expression regulation were associated with the concentration of osteopontin. CONCLUSION: A nearly 1.5-fold higher expression of CaR(surf) on the peripheral blood monocytes of individuals with diabetes and PAD manifests during post-transcription stage and depends on fasting glucose concentration and MCP-1 concentration on one hand, and the severity of PAD on the other.

Role of anti-HSP 60/65 antibodies in atherogenesis in patients with type 2 diabetes and lower limb ischemia.

The role of heat shock proteins and anti-HSP 60/65 antibodies in atherogenesis has been widely described in the literature, but the participation of these molecules in the pathogenesis of diabetic macroangiopathy has not been extensively investigated. 30 patients with type 2 diabetes complicated with macroangiopathy of the lower extremities in the intermittent claudication stage. The control group (n=18) consisted of healthy volunteers of corresponding age. Levels of anti-HSP 60/65 antibodies, von Willebrand factor (vWF) and hsCRP in blood serum were measured. We also assessed static effort based on isometric contraction lasting until full fatigue. In patients with lower limb ischemia in diabetic macroangiopathy, a positive correlation between anti-HSP 60/65 antibodies and von Willebrand factor levels in blood serum was found (R=0.543, p<0.05). Concentrations of anti-HSP 60/65 antibodies were higher than in the control group, but not statistically significant (44.77±55.00 vs. 26.09±13.85; NS). The ongoing disease process contributed statistically significantly to the strength of the quadriceps muscle of the thigh (21.47 vs. 27.82 for the right limb, and 20.27 vs. 28.33 for the left limb; p<0.05). Increased concentrations of anti-HSP 60/65 antibodies in blood serum suggests their involvement in the pathogenesis of diabetic macroangiopathy and correlates with the parameters of endothelial cell damage. In patients with type 2 diabetes complicated with atherosclerotic changes, a statistically significant reduction in lower limb muscle strength was found compared with the control group.

Cost of cooperation rules selection for cheats in bacterial metapopulations.

Bacteria secrete a large variety of beneficial metabolites into the environment, which can be shared as public goods among producing bacteria, but also be exploited by nonproducing cheats. Here, we focus on cooperative production of iron-chelating molecules (siderophores) in the bacterium Pseudomonas aeruginosa to study how relevant ecological factors influence selection for cheating. We designed patch-structured metapopulations that allowed us introducing among-patch ecological variation. We found that cheating readily evolved in uniform iron-limited environments. This finding is explained by severe iron limitation demanding high siderophore-production efforts, which results in high metabolic costs accruing to cooperators, and thereby facilitates the spread of cheats. In contrast, we observed a significant reduction or even negation of selection for cheating in metapopulations where we introduced patches with increased iron availability and/or opportunities to recycle siderophores. These findings are compatible with the view that cheats are less likely to invade in environments that allow bacteria to reduce siderophore-production efforts, as this lowers the overall metabolic costs accruing to cooperators. Because we increased iron availability and siderophore recycling opportunities moderately, and only in some patches, our findings demonstrate that already-small local variations in ecological conditions as occurring in nature can significantly affect selection for public-goods secretion in microbes. In addition, we found that most (84.6%) of the evolved cheats were partially deficient for siderophore production and not loss-of-function mutants. Genetic considerations indicate that mutations leading to partial deficiency occur more frequent than mutations leading to loss of function, but also suggest that partially deficient mutants might often be the more competitive cheats.

A cryptic heterogametic transition revealed by sex-linked DNA markers in Palearctic green toads.

In sharp contrast to birds and mammals, most cold-blooded vertebrates have homomorphic (morphologically undifferentiated) sex chromosomes. This might result either from recurrent X-Y recombination (occurring e.g. during occasional events of sex reversal) or from frequent turnovers (during which sex-determining genes are overthrown by new autosomal mutations). Evidence for turnovers is indeed mounting in fish, but very few have so far been documented in amphibians, possibly because of practical difficulties in identifying sex chromosomes. Female heterogamety (ZW) has long been established in Bufo bufo, based on sex reversal and crossing experiments. Here, we investigate a sex-linked marker identified from a laboratory cross between Palearctic green toads (Bufo viridis subgroup). The F(1) offspring produced by a female Bufo balearicus and a male Bufo siculus were phenotypically sexed, displaying an even sex ratio. A sex-specific marker detected in highly reproducible AFLP genotypes was cloned. Sequencing revealed a noncoding, microsatellite-containing fragment. Reamplification and genotyping of families of this and a reciprocal cross showed B. siculus to be male heterogametic (XY) and suggested the same system for B. balearicus. Our results thus reveal a cryptic heterogametic transition within bufonid frogs and help explain patterns of hybrid fitness within the B. viridis subgroup. Turnovers of genetic sex-determination systems may be more frequent in amphibians than previously thought and thus contribute to the prevalence of homomorphic sex chromosomes in this group.