Methyl farnesoate (MF) plays hormonal regulatory roles in crustaceans. An epoxidated form of MF, known as juvenile hormone (JH), controls metamorphosis and stimulates reproduction in insects. To address the evolutionary significance of MF epoxidation, we generated mosquitoes completely lacking either of the two enzymes that catalyze the last steps of MF/JH biosynthesis and epoxidation, respectively: the JH acid methyltransferase (JHAMT) and the P450 epoxidase CYP15 (EPOX). jhamt-/- larvae lacking both MF and JH died at the onset of metamorphosis. Strikingly, epox-/- mutants, which synthesized MF but no JH, completed the entire life cycle. While epox-/- adults were fertile, the reproductive performance of both sexes was dramatically reduced. Our results suggest that although MF can substitute for the absence of JH in mosquitoes, it is with a significant fitness cost. We propose that MF can fulfill most roles of JH, but its epoxidation to JH was a key innovation providing insects with a reproductive advantage.
- MeSH
- Aedes enzymologie genetika MeSH
- biologická proměna MeSH
- genetická zdatnost * MeSH
- juvenilní hormony biosyntéza MeSH
- molekulární evoluce * MeSH
- nenasycené mastné kyseliny metabolismus MeSH
- rozmnožování MeSH
- seskviterpeny metabolismus MeSH
- sexuální chování zvířat MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
During meiosis, the recombination-initiating DNA double-strand breaks (DSBs) are repaired by crossovers or noncrossovers (gene conversions). While crossovers are easily detectable, noncrossover identification is hampered by the small size of their converted tracts and the necessity of sequence polymorphism. We report identification and characterization of a mouse chromosome-wide set of noncrossovers by next-generation sequencing of 10 mouse intersubspecific chromosome substitution strains. Based on 94 identified noncrossovers, we determined the mean length of a conversion tract to be 32 bp. The spatial chromosome-wide distribution of noncrossovers and crossovers significantly differed, although both sets overlapped the known hotspots of PRDM9-directed histone methylation and DNA DSBs, thus supporting their origin in the standard DSB repair pathway. A significant deficit of noncrossovers descending from asymmetric DSBs proved their proposed adverse effect on meiotic recombination and pointed to sister chromatids as an alternative template for their repair. The finding has implications for the molecular mechanism of hybrid sterility in mice from crosses between closely related Mus musculus musculus and Mus musculus domesticus subspecies.
- MeSH
- chromozomy genetika MeSH
- dvouřetězcové zlomy DNA MeSH
- genetická zdatnost MeSH
- genová konverze * MeSH
- histonlysin-N-methyltransferasa genetika metabolismus MeSH
- histonový kód MeSH
- hybridizace genetická * MeSH
- meióza * MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic systems governing sexual differentiation vary among-and even within-species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.
- MeSH
- genetická zdatnost MeSH
- pohlavní chromozomy genetika MeSH
- procesy určující pohlaví genetika MeSH
- rekombinace genetická MeSH
- sexuální diferenciace genetika MeSH
- Xenopus genetika MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Geografické názvy
- Ghana MeSH
The interaction of house dust mites (HDM) and microorganisms is the key factor in the survival of these mites in human-made environments. Spent growth medium (SPGM) provides the rest of the diet, along with dead mite bodies and microorganisms. SPGM represents a source of microorganisms for the recolonization of mite food and the mite digestive tract. An experiment was performed to observe how adding SPGM to the HDM diet affects HDM population growth, the microbiome composition and the microbial respiration in microcosms. We analyzed American house dust mite (Dermatophagoides farinae) and European house dust mite (Dermatophagoides pteronyssinus) originating from control diets and diets treated with an extract of SPGM from 1- and 3-month-old mite cultures. The microbiome was described using 16S and 18S barcode sequencing. The composition of the bacterial and fungal microbiomes differed between the HDM species, but the SPGM treatment influenced only the bacterial profile of D. farinae. In the D. farinae microbiome of specimens on SPGM-treated diets compared to those of the control situation, the Lactobacillus profile decreased, while the Cardinium, Staphylococcus, Acinetobacter, and Sphingomonas profiles increased. The addition of SPGM extract decreased the microbial respiration in the microcosms with and without mites in almost all cases. Adding SPGM did not influence the population growth of D. farinae, but it had a variable effect on D. pteronyssinus. The results indicated that the HDM are marginally influenced by the microorganisms in their feces.
Chromozomové aberace jsou častou příčinou časných reprodukčních ztrát. Možnou přítomnost chromozomové aberace je možné ověřit cytogenetickým vyšetřením tkáně potraceného plodu. V rámci naší studie na Ústavu biologie a lékařské genetiky 1. lékařské fakulty Univerzity Karlovy a Všeobecné fakultní nemocnice v Praze jsme analyzovali vzorek tkáně u 233 případů časných spontánních či zamlklých potratů. Ve 212 případech byla kultivace úspěšná a celkem v 52 případech (24,5 %) byla zachycena chromozomová aberace – nejčastěji trizomie chromozomu 21, monozomie chromozomu X, triploidie a trizomie chromozomů 16 a 22. Celková četnost chromozomových aberací byla v našem souboru spíše nižší oproti obdobným studiím. I s ohledem na další ukazatele předpokládáme, že by příčinou mohla být kontaminace některých vzorků mateřskými buňkami, což ale nelze u rutinního cytogenetického vyšetření předem vyloučit. Dále jsme v rámci studie potvrdili vyšší četnost chromozomových aberací v případech s vyšším věkem matky a dále pak častější zastoupení chromozomových aberací v případech potratu ve vyšších týdnech těhotenství. Tyto nálezy byly statisticky významné.
Chromosomal aberrations are common cause of early miscarriage. Possible presence of chromosomal aberration may be assessed by cytogenetic examination of the aborted fetus tissue. In our study from the Institute of Biology and Medical Genetics of the First Faculty of Medicine of Charles University and General University Hospital in Prague we analysed tissue sample from 233 early spontaneous or missed abortions. In 212 cases the cultivation process was successful. Among those – we identified 52 cases with chromosomal aberration (24,5 %). Most common aberrations were – trisomy 21, monosomy X, triploidy and trisomies of chromosomes 16 and 22. Our overall incidence of aberrations was lower – compared to similar studies. According to other indicators we suppose that this may be caused by the higher incidence of maternal cells contamination – but this phenomenon cannot be completely excluded while using classical karyotyping. We also confirmed higher incidence of chromosomal aberrations in the miscarriage cases in elder mothers and furthermore we found higher incidence of aberrations in cases from higher gestation weeks. Both trends were statistically significant.
- Klíčová slova
- reprodukční ztráty,
- MeSH
- chromozomální aberace * embryologie klasifikace statistika a číselné údaje MeSH
- cytogenetické vyšetření statistika a číselné údaje MeSH
- genetická zdatnost MeSH
- karyotypizace statistika a číselné údaje MeSH
- lidé MeSH
- potracený plod abnormality cytologie MeSH
- retrospektivní studie MeSH
- rozmnožování genetika MeSH
- samovolný potrat epidemiologie etiologie MeSH
- těhotenství MeSH
- věkové faktory MeSH
- Check Tag
- lidé MeSH
- těhotenství MeSH
- Publikační typ
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
In genetic programming (GP), computer programs are often coevolved with training data subsets that are known as fitness predictors. In order to maximize performance of GP, it is important to find the most suitable parameters of coevolution, particularly the fitness predictor size. This is a very time-consuming process as the predictor size depends on a given application, and many experiments have to be performed to find its suitable size. A new method is proposed which enables us to automatically adapt the predictor and its size for a given problem and thus to reduce not only the time of evolution, but also the time needed to tune the evolutionary algorithm. The method was implemented in the context of Cartesian genetic programming and evaluated using five symbolic regression problems and three image filter design problems. In comparison with three different CGP implementations, the time required by CGP search was reduced while the quality of results remained unaffected.
- MeSH
- algoritmy * MeSH
- biologická evoluce * MeSH
- genetická zdatnost MeSH
- lidé MeSH
- počítačová simulace MeSH
- počítačové zpracování obrazu metody MeSH
- poměr signál - šum MeSH
- regresní analýza MeSH
- software * MeSH
- vylepšení obrazu metody MeSH
- výpočetní biologie metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Analysis of sublethal responses in cold-stressed insects can provide important information about fitness costs and a better understanding of the physiological mechanisms used to prevent and/or to cope with cold injury. Yet, such responses are understudied and often neglected in the literature. Here, we analyzed the effects of cold stress applied to larvae on the mortality/survival and fitness parameters of survivor adults of the vinegar fly, Drosophila melanogaster. Third instar larvae (either cold-sensitive or cold-acclimated) were exposed to either supercooling or freezing stress, both at -5 °C. A whole array of sublethal effects were observed, from mortality that occurs with some delay after cold stress, through delayed development to the pupal stage, to shortened life-span of the adult, and decreased female fecundity. Taking the sublethal effects into account improves the ecological meaningfulness of cold hardiness assay outcomes. For instance, we observed that although more than 80% of cold-acclimated larvae survive freezing to -5 °C, less than 10% survive until adulthood, and survivor females exhibit more than 50% reduction in their fecundity relative to controls. Female fecundity was positively correlated with dry mass and negatively correlated with total protein and glycogen stores. Hence, these parameters may serve as good predictors of survivor adult female fecundity. Further, we provide the concept of a two-component defense system, which (based on analysis of sublethal effects on fitness parameters) distinguishes between physiological mechanisms that help insects to resist (reduce or avoid) or tolerate (survive or repair) injuries linked to cold stress.
Allee effects have important implications for many aspects of basic and applied ecology. The benefits of aggregation of conspecific individuals are central to Allee effects, which have led to the widely held assumption that social species are more prone to Allee effects. Robust evidence for this assumption, however, remains rare. Furthermore, previous research on Allee effects has failed to adequately address the consequences of the different levels of organisation within social species' populations. Here, we review available evidence of Allee effects and model the role of demographic and behavioural factors that may combine to dampen or strengthen Allee effects in social species. We use examples across various species with contrasting social structure, including carnivores, bats, primates and eusocial insects. Building on this, we provide a conceptual framework that allows for the integration of different Allee effects in social species. Social species are characterised by nested levels of organisation. The benefits of cooperation, measured by mean individual fitness, can be observed at both the population and group levels, giving rise to "population level" and "group level" Allee effects respectively. We also speculate on the possibility of a third level, reporting per capita benefits for different individuals within a group (e.g. castes in social insects). We show that group size heterogeneity and intergroup interactions affect the strength of population-level demographic Allee effects. Populations with higher group size heterogeneity and in which individual social groups cooperate demonstrate the weakest Allee effects and may thus provide an explanation for why extinctions due to Allee effects are rare in social species. More adequately accounting for Allee effects in social species will improve our understanding of the ecological and evolutionary implications of cooperation in social species.
- MeSH
- biologická evoluce MeSH
- biologické modely MeSH
- genetická zdatnost * MeSH
- hmyz fyziologie MeSH
- hustota populace MeSH
- savci fyziologie MeSH
- sociální chování MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- MeSH
- biologická evoluce * MeSH
- ekologie * MeSH
- genetická zdatnost MeSH
- hustota populace MeSH
- populační dynamika MeSH
- rozmnožování MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- úvodníky MeSH
Sexually reproducing organisms require males and females to find each other. Increased difficulty of females finding mates as male density declines is the most frequently reported mechanism of Allee effects in animals. Evolving more effective mate search may alleviate Allee effects, but may depend on density regimes a population experiences. In particular, high-density populations may evolve mechanisms that induce Allee effects which become detrimental when populations are reduced and maintained at a low density. We develop an individual-based, eco-genetic model to study how mating systems and fitness trade-offs interact with changes in population density to drive evolution of the rate at which males or females search for mates. Finite mate search rate triggers Allee effects in our model and we explore how these Allee effects respond to such evolution. We allow a population to adapt to several population density regimes and examine whether high-density populations are likely to reverse adaptations attained at low densities. We find density-dependent selection in most of scenarios, leading to search rates that result in lower Allee thresholds in populations kept at lower densities. This mainly occurs when fecundity costs are imposed on mate search, and provides an explanation for why Allee effects are often observed in anthropogenically rare species. Optimizing selection, where the attained trait value minimizes the Allee threshold independent of population density, depended on the trade-off between search and survival, combined with monogamy when females were searching. Other scenarios led to runaway selection on the mate search rate, including evolutionary suicide. Trade-offs involved in mate search may thus be crucial to determining how density influences the evolution of Allee effects. Previous studies did not examine evolution of a trait related to the strength of Allee effects under density variation. We emphasize the crucial role that mating systems, fitness trade-offs and the evolving sex have in determining the density threshold for population persistence, in particular since evolution need not always take the Allee threshold to its minimum value.
- MeSH
- biologická evoluce * MeSH
- genetická zdatnost * MeSH
- hustota populace MeSH
- modely genetické MeSH
- sexuální výběr u zvířat * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
