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Changes in epigenetic states can allow individuals to cope with environmental changes. If such changes are heritable, this may lead to epigenetic adaptation. Thus, it is likely that in sessile organisms such as plants, part of the spatial epigenetic variation found across individuals will reflect the environmental heterogeneity within populations. The departure of the spatial epigenetic structure from the baseline genetic variation can help in understanding the value of epigenetic regulation in species with different breadth of optimal environmental requirements. Here, we hypothesise that in plants with narrow environmental requirements, epigenetic variability should be less structured in space given the lower variability in suitable environmental conditions. We performed a multispecies study that considered seven pairs of congeneric plant species, each encompassing a narrow endemic with habitat specialisation and a widespread species. In three populations per species we used AFLP and methylation-sensitive AFLP markers to characterise the spatial genetic and epigenetic structures. Narrow endemics showed a significantly lower epigenetic than genetic differentiation between populations. Within populations, epigenetic variation was less spatially structured than genetic variation, mainly in narrow endemics. In these species, structural equation models revealed that such pattern was associated to a lack of correlation between epigenetic and genetic information. Altogether, these results show a greater decoupling of the spatial epigenetic variation from the baseline spatial genetic pattern in endemic species. These findings highlight the value of studying genetic and epigenetic spatial variation to better understand habitat specialisation in plants.
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Epigênese Genética , Variação Genética , Humanos , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Metilação de DNA , EcossistemaRESUMO
BACKGROUND: We analyzed the long-term influence of fixation systems on proximal aortic neck (PAN) evolution by comparing 2 late-generation endoprostheses, Endurant (Medtronic Vascular, Minneapolis, Minn) with suprarenal fixation (SRF) and Excluder (W.L Gore & Associates, Flagstaff, Ariz) with infrarenal fixation (IRF). METHODS: Our retrospective observational study included consecutive patients undergoing endovascular aneurysm repair (EVAR) for aorto-iliac aneurysms (2011-2020). Primary end points: neck enlargement and freedom from significative PAN enlargement (5 mm). Secondary end points: neck-related reintervention, endoleaks and graft migration. Results were reported following the Society of Vascular Surgery reporting standards. RESULTS: 139 patients were included (97 in SRF group and 42 in IRF group). A difference in growth at 10 mm caudal to lowest renal artery at 2 years follow-up was found (mean growth of 1.92 ± 3.38 mm in SRF and 0.16 ± 6.86 mm in IRF; P < 0.001). A tendency to a major growth in SRF at 4 years follow-up at the lowest renal artery (1.27 ± 3.36 mm vs. 0.63 ± 2.2 mm; P = 0.06), 5 mm distal to lowest renal artery (2.17 ± 3.52 mm vs. 0.94 ± 2.76 mm; P = 0.001) and 10 mm distal to lowest renal artery (2.65 ± 3.86 mm vs. 1.12 ± 1.5 mm; P < 0.001) was shown. Freedom from PAN enlargement was 96.65% and 88.20% in SRF and 100% and 94.4% in IRF at 2 and 4 years follow-up respectively (log rank 0.041). A greater incidence of type II endoleaks in IRF was observed (40.48% vs. 15.46%; P = 0.001). Oversizing >15% showed to be a risk factor of PAN enlargement (odds ratio 6.85; 95% confident interval: 1.67-28.4; P = 0.007). CONCLUSIONS: A small but significative percentage of patients after EVAR show a progressive PAN enlargement, being significatively greater in SRF, without increasing neck-related complications 4 years after graft deployment.
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Aortoesophageal fistula (AEF) secondary to thoracic endovascular aortic repair (TEVAR) is a rare clinical entity that poses a threat to life as it causes massive digestive bleeding, and it is estimated that 60% of patients who suffer from it could die within within 6 months of the onset of their symptoms. It requires a high clinical suspicion to establish an early multidisciplinary surgical treatment. We present the cases of two patients diagnosed with aortoesophageal fistulas after TEVAR in the last 5 years (January 2018-December 2022) while reviewing the existing scientific literature on the matter.
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Doenças da Aorta , Procedimentos Endovasculares , Fístula Esofágica , Fístula Vascular , Humanos , Correção Endovascular de Aneurisma , Fístula Vascular/diagnóstico por imagem , Fístula Vascular/etiologia , Procedimentos Endovasculares/efeitos adversos , Doenças da Aorta/diagnóstico por imagem , Doenças da Aorta/etiologia , Doenças da Aorta/cirurgia , Fístula Esofágica/diagnóstico por imagem , Fístula Esofágica/etiologia , Hemorragia/complicaçõesRESUMO
The interspecific range of epigenetic variation and the degree to which differences between angiosperm species are related to geography, evolutionary history, ecological settings or species-specific traits, remain essentially unexplored. Genome-wide global DNA cytosine methylation is a tractable 'epiphenotypic' feature suitable for exploring these relationships. Global cytosine methylation was estimated in 279 species from two distant, ecologically disparate geographical regions: Mediterranean Spain and tropical México. At each region, four distinct plant communities were analyzed. Global methylation spanned a 10-fold range among species (4.8-42.2%). Interspecific differences were related to evolutionary trajectories, as denoted by a strong phylogenetic signal. Genomes of tropical species were on average less methylated than those of Mediterranean ones. Woody plants have genomes with lower methylation than perennial herbs, and genomes of widespread species were less methylated than those of species with restricted geographical distribution. The eight communities studied exhibited broad and overlapping interspecific variances in global cytosine methylation and only two of them differed in average methylation. Altogether, our broad taxonomic survey supported global methylation as a plant 'epiphenotypic' trait largely associated with species evolutionary history, genome size, range size and woodiness. Additional studies are required for better understanding the environmental components underlying local and geographical variation.
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Ecossistema , Magnoliopsida/genética , Magnoliopsida/fisiologia , Plantas/classificação , Plantas/genética , Clima Tropical , Metilação de DNA , Demografia , Regulação da Expressão Gênica de Plantas , Região do MediterrâneoRESUMO
PREMISE: Phenotypic heterogeneity of reiterated, homologous structures produced by individual plants has ecological consequences for plants and their animal consumers. This paper examines experimentally the epigenetic mosaicism hypothesis, which postulates that within-plant variation in traits of reiterated structures may partly arise from different parts of the same genetic individual differing in patterns or extent of genomic DNA methylation. METHODS: Leaves of paired ramets borne by field-growing Helleborus foetidus plants were infiltrated periodically over the entire flowering period with either a water solution of the demethylating agent zebularine or just water as the control. The effects of the zebularine treatment were assessed by quantifying genome-wide DNA cytosine methylation in leaves and monitoring inflorescence growth and flower production, number of ovules per flower, pollination success, fruit set, seed set, seed size, and distribution of sap-feeding insects. RESULTS: Genomic DNA from leaves in zebularine-treated ramets was significantly less methylated than DNA from leaves in control ones. Inflorescences in treated ramets grew smaller and produced fewer flowers, with fewer ovules and lower follicle and seed set, but did not differ from inflorescences in untreated ramets in pollination success or seed size. The zebularine treatment influenced the within-plant distribution of sap-feeding insects. CONCLUSIONS: Experimental manipulation of genomic DNA methylation level in leaves of wild-growing H. foetidus plants induced considerable within-plant heterogeneity in phenotypic (inflorescences, flowers, fecundity) and ecologically relevant traits (herbivore distribution), which supports the hypothesis that epigenetic mosaicism may partly account for within-plant variation.
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Citosina/metabolismo , Metilação de DNA , Epigênese Genética , Fertilidade/genética , Helleborus/fisiologia , Herbivoria/fisiologia , Flores/genética , Flores/fisiologia , Helleborus/genética , Inflorescência/genética , Inflorescência/fisiologia , Mosaicismo , Folhas de Planta/fisiologia , Sementes/genética , Sementes/fisiologiaRESUMO
Background and Aims: Sub-individual variation in traits of homologous structures has multiple ecological consequences for individuals and populations. Assessing the evolutionary significance of such effects requires an improved knowledge of the mechanisms underlying within-plant phenotypic heterogeneity. The hypothesis that continuous within-plant variation in some phenotypic traits can be associated with epigenetic mosaicism was examined. Methods: Fifteen individuals of the long-lived, evergreen Mediterranean shrub Lavandula latifolia were studied. Five widely spaced 'modules', each consisting of a single inflorescence plus all its subtending basal leaves, were collected from each shrub. Genomic DNA was extracted from leaf samples and genome-wide cytosine methylation determined by reversed phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The number and mean mass of seeds produced were determined for each inflorescence. An assessment was made of whether (1) leaves from different modules in the same plant differed significantly in global DNA cytosine methylation, and (2) mosaicism in cytosine methylation contributed to explain variation across modules in number and size of seeds. Key Results: Leaves from different modules in the same plant differed in global DNA cytosine methylation. The magnitude of epigenetic mosaicism was substantial, as the variance in DNA methylation among modules of the same shrub was greater than the variance between individuals. Number and mean mass of seeds produced by individual inflorescences varied within plants and were quadratically related to cytosine methylation of subtending leaves, with an optimum at an intermediate methylation level (approx. 25 %). Conclusions: The results support a causal link between global cytosine methylation of leaves in a module and the size and numbers of seeds produced by the associated inflorescence. It is proposed that variation in global DNA methylation within L. latifolia shrubs may result from the concerted action of plant sectoriality and differential exposure of different plant parts to some environmental factor(s) with a capacity to induce durable epigenetic changes.
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Epigênese Genética , Flores/anatomia & histologia , Lavandula/anatomia & histologia , Mosaicismo , Sementes/anatomia & histologia , Metilação de DNA , DNA de Plantas/genética , Epigênese Genética/genética , Flores/genética , Flores/fisiologia , Lavandula/genética , Lavandula/fisiologia , Fenótipo , Reprodução , Sementes/genéticaRESUMO
PREMISE OF THE STUDY: The ecological and evolutionary significance of natural epigenetic variation (i.e., not based on DNA sequence variants) variation will depend critically on whether epigenetic states are transmitted from parents to offspring, but little is known on epigenetic inheritance in nonmodel plants. METHODS: We present a quantitative analysis of transgenerational transmission of global DNA cytosine methylation (= proportion of all genomic cytosines that are methylated) and individual epigenetic markers (= methylation status of anonymous MSAP markers) in the shrub Lavandula latifolia. Methods based on parent-offspring correlations and parental variance component estimation were applied to epigenetic features of field-growing plants ('maternal parents') and greenhouse-grown progenies. Transmission of genetic markers (AFLP) was also assessed for reference. KEY RESULTS: Maternal parents differed significantly in global DNA cytosine methylation (range = 21.7-36.7%). Greenhouse-grown maternal families differed significantly in global methylation, and their differences were significantly related to maternal origin. Methylation-sensitive amplified polymorphism (MSAP) markers exhibited significant transgenerational transmission, as denoted by significant maternal variance component of marker scores in greenhouse families and significant mother-offspring correlations of marker scores. CONCLUSIONS: Although transmission-related measurements for global methylation and MSAP markers were quantitatively lower than those for AFLP markers taken as reference, this study has revealed extensive transgenerational transmission of genome-wide global cytosine methylation and anonymous epigenetic markers in L. latifolia. Similarity of results for global cytosine methylation and epigenetic markers lends robustness to this conclusion, and stresses the value of considering both types of information in epigenetic studies of nonmodel plants.
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Citosina/metabolismo , Metilação de DNA , Epigênese Genética , Lavandula/genética , Metilação de DNA/genética , Epigênese Genética/genética , Marcadores Genéticos/genética , Variação Genética/genética , Lavandula/metabolismoRESUMO
PREMISE OF THE STUDY: Epigenetic variation can play a role in local adaptation; thus, there should be associations among epigenetic variation, environmental variation, and functional trait variation across populations. This study examines these relationships in the perennial herb Helleborus foetidus (Ranunculaceae). METHODS: Plants from 10 subpopulations were characterized genetically (AFLP, SSR markers), epigenetically (MSAP markers), and phenotypically (20 functional traits). Habitats were characterized using six environmental variables. Isolation-by-distance (IBD) and isolation-by-environment (IBE) patterns of genetic and epigenetic divergence were assessed, as was the comparative explanatory value of geographical and environmental distance as predictors of epigenetic, genetic, and functional differentiation. KEY RESULTS: Subpopulations were differentiated genetically, epigenetically, and phenotypically. Genetic differentiation was best explained by geographical distance, while epigenetic differentiation was best explained by environmental distance. Divergence in functional traits was correlated with environmental and epigenetic distances, but not with geographical and genetic distances. CONCLUSIONS: Results are compatible with the hypothesis that epigenetic IBE and functional divergence reflected responses to environmental variation. Spatial analyses simultaneously considering epigenetic, genetic, phenotypic and environmental information provide a useful tool to evaluate the role of environmental features as drivers of natural epigenetic variation between populations.
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Despite the recent upsurge of interest on natural epigenetic variation of nonmodel organisms, factors conditioning the spatial structure of epigenetic diversity in wild plant populations remain virtually unexplored. We propose that information on processes shaping natural epigenetic variation can be gained using the spatial structure of genetic diversity as null model. Departures of epigenetic isolation-by-distance (IBD) patterns from genetic IBD patterns for the same sample, particularly differences in slope of similarity-distance regressions, will reflect the action of factors that operate specifically on epigenetic variation, including imperfect transgenerational inheritance and responsiveness to environmental factors of epigenetic marks. As a proof of concept, we provide a comparative analysis of spatial genetic and epigenetic structure of 200 mapped individuals of the perennial herb Helleborus foetidus. Plants were fingerprinted using nuclear microsatellites, amplified fragment length polymorphisms (AFLP) and methylation-sensitive AFLP markers. Expectations from individual-level IBD patterns were tested by means of kinship-distance regressions. Both genetic and epigenetic similarity between H. foetidus individuals conformed to theoretical expectations under individual-level IBD models. Irrespective of marker type, there were significant negative linear relationships between the kinship coefficient for plant pairs and their spatial separation. Regression slopes were significantly steeper for epigenetic markers. Epigenetic similarity between individuals was much greater than genetic similarity at shortest distances, such epigenetic 'kinship excess' tending to decrease as plant separation increased. Results suggest that moderate-to-high heritability and responsiveness to local environments are major drivers of epigenetic spatial structure in H. foetidus, and illustrate the heuristic value of comparing genetic and epigenetic spatial structure for formulating and testing hypotheses on forces shaping epigenetic diversity in wild plant populations.
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Epigênese Genética , Genética Populacional , Helleborus/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Impressões Digitais de DNA , Metilação de DNA , DNA de Plantas/genética , Variação Genética , Heurística , Repetições de Microssatélites , Análise EspacialRESUMO
PREMISE OF THE STUDY: Continuous within-plant variation in quantitative traits of reiterated, homologous structures is a component of intraspecific variation, but its contribution to functional diversity remains largely unexplored. For the perennial Helleborus foetidus, we measured functional leaf traits to quantify the contribution of within-plant variation to intraspecific functional variance and evaluate whether within-plant variability itself deserves separate consideration. METHODS: Within-individual variation in eight leaf traits was quantified for 138 plants sampled from 10 widely spaced locations in the Sierra de Cazorla, southeastern Spain. An amplified fragment length polymorphism (AFLP) technique was used to look for associations between within-plant variability and specific AFLP markers. KEY RESULTS: Leaflets from basal positions in ramets were longer, heavier, had greater surface area and larger stomata, and lower specific area, stomatal index, and stomatal density than those from distal positions. Continuous variation between leaves from the same ramet was the main source of population-wide variance for most traits. Within-plant variability differed among populations. Individuals differed in within-plant variability, which was largely independent of trait means and associated with genetic characteristics. Up to four AFLP markers were associated with the within-plant variability level of a given leaf trait. CONCLUSIONS: Subindividual variability in continuous leaf traits was independent of plant means and related to genetic features. The within-individual component generally exceeded the between-individual component of intraspecific variance. Within-plant variation may broaden the ecological breadth and enhance stability and persistence of plant populations and communities and may provide novel insights when incorporated in trait-based community ecology models.
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DNA de Plantas/análise , Helleborus/genética , Fenótipo , Folhas de Planta/anatomia & histologia , Polimorfismo Genético , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Ecologia , Epigênese Genética , Helleborus/anatomia & histologia , Estômatos de Plantas , EspanhaRESUMO
The ecological significance of epigenetic variation has been generally inferred from studies on model plants under artificial conditions, but the importance of epigenetic differences between individuals as a source of intraspecific diversity in natural plant populations remains essentially unknown. This study investigates the relationship between epigenetic variation and functional plant diversity by conducting epigenetic (methylation-sensitive amplified fragment length polymorphisms, MSAP) and genetic (amplified fragment length polymorphisms, AFLP) marker-trait association analyses for 20 whole-plant, leaf and regenerative functional traits in a large sample of wild-growing plants of the perennial herb Helleborus foetidus from ten sampling sites in south-eastern Spain. Plants differed widely in functional characteristics, and exhibited greater epigenetic than genetic diversity, as shown by per cent polymorphism of MSAP fragments (92%) or markers (69%) greatly exceeding that for AFLP ones (41%). After controlling for genetic structuring and possible cryptic relatedness, every functional trait considered exhibited a significant association with at least one AFLP or MSAP marker. A total of 27 MSAP (13.0% of total) and 12 AFLP (4.4%) markers were involved in significant associations, which explained on average 8.2% and 8.0% of trait variance, respectively. Individual MSAP markers were more likely to be associated with functional traits than AFLP markers. Between-site differences in multivariate functional diversity were directly related to variation in multilocus epigenetic diversity after multilocus genetic diversity was statistically accounted for. Results suggest that epigenetic variation can be an important source of intraspecific functional diversity in H. foetidus, possibly endowing this species with the capacity to exploit a broad range of ecological conditions despite its modest genetic diversity.
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Epigênese Genética , Helleborus/genética , Polimorfismo Genético , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Metilação de DNA , DNA de Plantas/genética , Marcadores Genéticos , Fenótipo , Análise de Sequência de DNA , EspanhaRESUMO
Inferences about the role of epigenetics in plant ecology and evolution are mostly based on studies of cultivated or model plants conducted in artificial environments. Insights from natural populations, however, are essential to evaluate the possible consequences of epigenetic processes in biologically realistic scenarios with genetically and phenotypically heterogeneous populations. Here, we explore associations across individuals between DNA methylation transmissibility (proportion of methylation-sensitive loci whose methylation status persists unchanged after male gametogenesis), genetic characteristics (assessed with AFLP markers), seed size variability (within-plant seed mass variance), and realized maternal fecundity (number of recently recruited seedlings), in three populations of the perennial herb Helleborus foetidus along a natural ecological gradient in southeastern Spain. Plants (sporophytes) differed in the fidelity with which DNA methylation was transmitted to descendant pollen (gametophytes). This variation in methylation transmissibility was associated with genetic differences. Four AFLP loci were significantly associated with transmissibility and accounted collectively for ~40% of its sample-wide variance. Within-plant variance in seed mass was inversely related to individual transmissibility. The number of seedlings recruited by individual plants was significantly associated with transmissibility. The sign of the relationship varied between populations, which points to environment-specific, divergent phenotypic selection on epigenetic transmissibility. Results support the view that epigenetic transmissibility is itself a phenotypic trait whose evolution may be driven by natural selection, and suggest that in natural populations epigenetic and genetic variation are two intertwined, rather than independent, evolutionary factors.
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Metilação de DNA , Epigênese Genética , Heterogeneidade Genética , Helleborus/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA de Plantas/genética , Fertilidade/genética , Genética Populacional , Helleborus/fisiologia , Pólen/genética , Sementes/fisiologia , EspanhaRESUMO
UNLABELLED: ⢠PREMISE OF THE STUDY: Few studies have examined how epigenetic modifications of DNA may influence individual plant phenotypes and ecological processes in wild plant populations. We investigated natural variation in global DNA cytosine methylation and its phenotypic correlates in the perennial herb Helleborus foetidus.⢠METHODS: We focused specifically on individual differences in size- and fecundity-related traits and used HPLC to quantify percentage of total cytosines in the genome of young full-grown leaves that were methylated.⢠KEY RESULTS: About one third of all cytosines in H. foetidus genome were methylated. Methylation level differed significantly among individual plants (range = 26.4-36.6%; n = 60 plants), and this variation was significantly related to most size- and fecundity-related traits considered. Relatively hypomethylated plants bore more vegetative, reproductive, and total ramets, produced more flowers, larger inflorescences and more seed-bearing follicles, and their ramets remained vegetative for fewer years before reproducing sexually, than relatively hypermethylated ones. Taken together, results revealed that individual differences in size and reproductive output were inversely related to global cytosine methylation.⢠CONCLUSIONS: These results confirm, in a natural scenario, the association between DNA methylation and size- and fecundity-related traits that was previously found by experimental studies. Variations in global cytosine methylation were predictably related to individual differences in sexual reproduction through significant effects on flower and fruit production, which might ultimately influence patterns of selection and population dynamics in this species. This study provides novel insights on the potential ecological significance of epigenetic heterogeneity in wild plant populations.
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Citosina/metabolismo , Metilação de DNA , DNA de Plantas/metabolismo , Genoma de Planta , Helleborus/genética , Fenótipo , Epigênese Genética , Fertilidade , Flores , Helleborus/metabolismo , Helleborus/fisiologia , Folhas de Planta , Ranunculaceae , Reprodução/genéticaRESUMO
Through their effects on physicochemical features of floral nectar, nectar-dwelling yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar yeasts on foraging patterns of captive and free-ranging bumble bees, and also on pollination success and fecundity of the early-blooming, bumble bee-pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast-containing artificial flowers. Free-ranging bumble bees also preferred yeast-containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing yeasts were more thoroughly removed than nectars without yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect-pollinated plants.
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Abelhas/fisiologia , Flores/microbiologia , Flores/fisiologia , Helleborus/fisiologia , Néctar de Plantas/análise , Leveduras/isolamento & purificação , Animais , Helleborus/microbiologia , Reprodução/fisiologiaRESUMO
DNA cytosine methylation is an epigenetic mechanism involved in regulation of plant responses to biotic and abiotic stress and its ability to change can vary with the sequence context in which a cytosine appears (CpG, CHG, CHH, where H = Adenine, Thymine, Cytosine). Quantification of DNA methylation in model plant species is frequently addressed by Whole Genome Bisulfite Sequencing (WGBS), which requires a good-quality reference genome. Reduced Representation Bisulfite Sequencing (RRBS) is a cost-effective potential alternative for ecological research with limited genomic resources and large experimental designs. In this study, we provide for the first time a comprehensive comparison between the outputs of RRBS and WGBS to characterize DNA methylation changes in response to a given environmental factor. In particular, we used epiGBS (recently optimized RRBS) and WGBS to assess global and sequence-specific differential methylation after insect and artificial herbivory in clones of Populus nigra cv. 'italica'. We found that, after any of the two herbivory treatments, global methylation percentage increased in CHH, and the shift was detected as statistically significant only by epiGBS. As regards to loci-specific differential methylation induced by herbivory (cytosines in epiGBS and regions in WGBS), both techniques indicated the specificity of the response elicited by insect and artificial herbivory, together with higher frequency of hypo-methylation in CpG and hyper-methylation in CHH. Methylation changes were mainly found in gene bodies and intergenic regions when present at CpG and CHG and in transposable elements and intergenic regions at CHH context. Thus, epiGBS succeeded to characterize global, genome-wide methylation changes in response to herbivory in the Lombardy poplar. Our results support that epiGBS could be particularly useful in large experimental designs aimed to explore epigenetic changes of non-model plant species in response to multiple environmental factors.
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Herbivoria , Populus , Populus/genética , Metilação de DNA , Citosina , DNA IntergênicoRESUMO
Genetic diversity defines the evolutionary potential of a species, yet mounting evidence suggests that epigenetic diversity could also contribute to adaptation. Elucidating the complex interplay between genetic and epigenetic variation in wild populations remains a challenge for evolutionary biologists, and the intriguing possibility that epigenetic diversity could compensate for the loss of genetic diversity is one aspect that remains basically unexplored in wild plants. This hypothesis is addressed in this paper by comparing the extent and patterns of genetic and epigenetic diversity of phylogenetically closely related but ecologically disparate species. Seven pairs of congeneric species from Cazorla mountains in south-eastern Spain were studied, each pair consisting of one endemic, restricted-range species associated to stressful environments, and one widespread species occupying more favourable habitats. The prediction was tested that endemic species should have lower genetic diversity due to population fragmentation, and higher epigenetic diversity induced by environmental stress, than their widespread congeners. Genetic (DNA sequence variants) and epigenetic (DNA cytosine methylation variants) diversities and their possible co-variation were assessed in three populations of each focal species using amplified fragment length polymorphism (AFLP) and methylation-sensitive AFLP (MSAP). All species and populations exhibited moderate to high levels of genetic polymorphism irrespective of their ecological characteristics. Epigenetic diversity was greater than genetic diversity in all cases. Only in endemic species were the two variables positively related, but the difference between epigenetic and genetic diversity was greater at populations with low genetic polymorphism. Results revealed that the relationship between genetic and epigenetic diversity can be more complex than envisaged by the simple hypothesis addressed in this study, and highlight the need of additional research on the actual role of epigenetic variation as a source of phenotypic diversity before a realistic understanding of the evolutionary relevance of epigenetic phenomena in plant adaptation can be achieved.
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BACKGROUND AND AIMS: High mountain ranges of the Mediterranean Basin harbour a large number of narrowly endemic plants. In this study an investigation is made of the levels and partitioning of genetic diversity in Narcissus longispathus, a narrow endemic of south-eastern Spanish mountains characterized by a naturally fragmented distribution due to extreme specialization on a rare habitat type. By using dense sampling of populations across the species' whole geographical range, genetic structuring at different geographical scales is also examined. METHODS: Using horizontal starch-gel electrophoresis, allozyme variability was screened at 19 loci for a total of 858 individuals from 27 populations. The data were analysed by means of standard statistical approaches in order to estimate gene diversity and the genetic structure of the populations. KEY RESULTS: Narcissus longispathus displayed high levels of genetic diversity and extensive diversification among populations. At the species level, the percentage of polymorphic loci was 68 %, with average values of 2.1, 0.11 and 0.14 for the number of alleles per locus, observed heterozygosity and expected heterozygosity, respectively. Southern and more isolated populations tended to have less genetic variability than northern and less-isolated populations. A strong spatial patterning of genetic diversity was found at the various spatial scales. Gene flow/drift equilibrium occurred over distances <4 km. Beyond that distance divergence was relatively more influenced by drift. The populations studied seem to derive from three panmictic units or 'gene pools', with levels of admixture being greatest in the central and south-eastern portions of the species' range. CONCLUSIONS: In addition to documenting a case of high genetic diversity in a narrow endemic plant with naturally fragmented populations, the results emphasize the need for dense population sampling and examination of different geographical scales for understanding population genetic structure in habitat specialists restricted to ecological islands.
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Fluxo Gênico , Deriva Genética , Variação Genética , Narcissus/genética , Ecossistema , Eletroforese em Gel de Amido , Geografia , Polimorfismo Genético , Análise de Regressão , EspanhaRESUMO
Methylation of DNA cytosines affects whether transposons are silenced and genes are expressed, and is a major epigenetic mechanism whereby plants respond to environmental change. Analyses of methylation-sensitive amplification polymorphism (MS-AFLP or MSAP) have been often used to assess methyl-cytosine changes in response to stress treatments and, more recently, in ecological studies of wild plant populations. MSAP technique does not require a sequenced reference genome and provides many anonymous loci randomly distributed over the genome for which the methylation status can be ascertained. Scoring of MSAP data, however, is not straightforward, and efforts are still required to standardize this step to make use of the potential to distinguish between methylation at different nucleotide contexts. Furthermore, it is not known how accurately MSAP infers genome-wide cytosine methylation levels in plants. Here, we analyse the relationship between MSAP results and the percentage of global cytosine methylation in genomic DNA obtained by HPLC analysis. A screening of literature revealed that methylation of cytosines at cleavage sites assayed by MSAP was greater than genome-wide estimates obtained by HPLC, and percentages of methylation at different nucleotide contexts varied within and across species. Concurrent HPLC and MSAP analyses of DNA from 200 individuals of the perennial herb Helleborus foetidus confirmed that methyl-cytosine was more frequent in CCGG contexts than in the genome as a whole. In this species, global methylation was unrelated to methylation at the inner CG site. We suggest that global HPLC and context-specific MSAP methylation estimates provide complementary information whose combination can improve our current understanding of methylation-based epigenetic processes in nonmodel plants.
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Análise do Polimorfismo de Comprimento de Fragmentos Amplificados/métodos , Citosina/metabolismo , Metilação de DNA , Helleborus/genética , Marcadores Genéticos , Genoma de Planta , Helleborus/classificação , Helleborus/metabolismoRESUMO
Despite the importance of assessing the stability of epigenetic variation in non-model organisms living in real-world scenarios, no studies have been conducted on the transgenerational persistence of epigenetic structure in wild plant populations. This gap in knowledge is hindering progress in the interpretation of natural epigenetic variation. By applying the methylation-sensitive amplified fragment length polymorphism (MSAP) technique to paired plant-pollen (i.e., sporophyte-male gametophyte) DNA samples, and then comparing methylation patterns and epigenetic population differentiation in sporophytes and their descendant gametophytes, we investigated transgenerational constancy of epigenetic structure in three populations of the perennial herb Helleborus foetidus (Ranunculaceae). Single-locus and multilocus analyses revealed extensive epigenetic differentiation between sporophyte populations. Locus-by-locus comparisons of methylation status in individual sporophytes and descendant gametophytes showed that ~75% of epigenetic markers persisted unchanged through gametogenesis. In spite of some epigenetic reorganization taking place during gametogenesis, multilocus epigenetic differentiation between sporophyte populations was preserved in the subsequent gametophyte stage. In addition to illustrating the efficacy of applying the MSAP technique to paired plant-pollen DNA samples to investigate epigenetic gametic inheritance in wild plants, this paper suggests that epigenetic differentiation between adult plant populations of H. foetidus is likely to persist across generations.
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Diferenciação Celular/genética , DNA de Plantas/genética , Epigênese Genética , Gametogênese , Helleborus/genética , Pólen/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Metilação de DNA , Ecossistema , Loci Gênicos , Polimorfismo GenéticoRESUMO
This article documents the addition of 153 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Brassica oleracea, Brycon amazonicus, Dimorphandra wilsonii, Eupallasella percnurus, Helleborus foetidus, Ipomoea purpurea, Phrynops geoffroanus, Prochilodus argenteus, Pyura sp., Sylvia atricapilla, Teratosphaeria suttonii, Trialeurodes vaporariorum and Trypanosoma brucei. These loci were cross-tested on the following species: Dimorphandra coccicinea, Dimorphandra cuprea, Dimorphandra gardneriana, Dimorphandra jorgei, Dimorphandra macrostachya, Dimorphandra mollis, Dimorphandra parviflora and Dimorphandra pennigera.