Transgenerational Effects of Stress Exposure on Offspring Phenotypes in Apomictic Dandelion

Heritable epigenetic modulation of gene expression is a candidate mechanism to explain parental environmental effects on offspring phenotypes, but current evidence for environment-induced epigenetic changes that persist in offspring generations is scarce. In apomictic dandelions, exposure to various stresses was previously shown to heritably alter DNA methylation patterns. In this study we explore whether these induced changes are accompanied by heritable effects on offspring phenotypes. We observed effects of parental jasmonic acid treatment on offspring specific leaf area and on offspring interaction with a generalist herbivore; and of parental nutrient stress on offspring root-shoot biomass ratio, tissue P-content and leaf morphology. Some of the effects appeared to enhance offspring ability to cope with the same stresses that their parents experienced. Effects differed between apomictic genotypes and were not always consistently observed between different experiments, especially in the case of parental nutrient stress. While this context-dependency of the effects remains to be further clarified, the total set of results provides evidence for the existence of transgenerational effects in apomictic dandelions. Zebularine treatment affected the within-generation response to nutrient stress, pointing at a role of DNA methylation in phenotypic plasticity to nutrient environments. This study shows that stress exposure in apomictic dandelions can cause transgenerational phenotypic effects, in addition to previously demonstrated transgenerational DNA methylation effects

Some like it hot: adaptation to the urban heat island in common dandelion.

The Urban Heat Island Effect (UHIE) is a globally consistent pressure on species living in cities. Rapid adaptation to the UHIE may be necessary for urban wild flora to persist in cities, but experimental evidence is lacking. Here, we report the first evidence of genetic differentiation in a plant species in response to the UHIE. We collected seeds from common dandelion (Taraxacum officinale) individuals along an urban-rural gradient in the city of Amsterdam (The Netherlands). In common-environment greenhouse experiments, we assessed the effect of elevated temperatures on plant growth and the effect of vernalisation treatments on flowering phenology. We found that urban plants accumulate more biomass at higher temperatures and require shorter vernalisation to induce flowering compared to rural plants. Differentiation was also observed between different intra-urban subhabitats, with park plants displaying a higher vernalisation requirement than street plants. Our results show strong differentiation between urban and rural dandelions in temperature-dependent growth and phenology, consistent with adaptive divergence in response to the UHIE. Rapid adaptation to the UHIE may be a potential explanation for the widespread success of dandelions in urban environments

Data from: Effects of admixture in native and invasive populations of Lythrum salicaria

Intraspecific hybridization between diverged populations can enhance fitness via various genetic mechanisms. The benefits of such admixture have been proposed to be particularly relevant in biological invasions, when invasive populations originating from different source populations are found sympatrically. However, it remains poorly understood if admixture is an important contributor to plant invasive success and how admixture effects compare between invasive and native ranges. Here, we used experimental crosses in Lythrum salicaria, a species with well-established history of multiple introductions to Eastern North America, to quantify and compare admixture effects in native European and invasive North American populations. We observed heterosis in between-population crosses both in native and invasive ranges. However, invasive-range heterosis was restricted to crosses between two different Eastern and Western invasion fronts, whereas heterosis was absent in geographically distant crosses within a single large invasion front. Our results suggest that multiple introductions have led to already-admixed invasion fronts, such that experimental crosses do not further increase performance, but that contact between different invasion fronts further enhances fitness after admixture. Thus, intra-continental movement of invasive plants in their introduced range has the potential to boost invasiveness even in well-established and successfully spreading invasive species

Experiment 3: ANOVA test results for effects of nutrient limitation and parental nutrient limitation on offspring traits in AS34, as affected by germination in different zebularine concentrations.

<p>Error degrees of freedom = 110, model term degrees of freedom are in parentheses.</p

Experiment 1: effect of parental nutrient stress on offspring traits.

<p>Leaf length (a); shoot biomass (b); specific leaf area (c); root ∶ shoot ratio (d); and shoot phosphorus content (e), of offspring grown under control conditions (grey bars, offspring environment ‘C’) and nutrient stress (open bars, offspring environment ‘N’) (means ± SEM). P values are shown for tests of parental environment and the parental environment×offspring environment interaction.</p

Experiment 1: effect of parental salt stress on offspring traits.

<p>Leaf length (a); shoot biomass (b); specific leaf area (c); and root ∶ shoot ratio (d), of offspring plants grown under control conditions (grey bars, offspring environment ‘C’) and high-salt stress (open bars, offspring environment ‘S’) (means ± SEM). P values are shown for tests of parental environment and the parental environment×offspring environment interaction.</p

Experiment 1: effects of parental JA and SA treatment on traits of offspring raised in common control environments (experiment 1, genotype AS34; means ± SEM).

<p>Experiment 1: effects of parental JA and SA treatment on traits of offspring raised in common control environments (experiment 1, genotype AS34; means ± SEM).</p

Experiment 2: effect of parental nutrient stress on offspring.

<p>Root ∶ shoot biomass ratio (a) and leaf length (b) in three apomictic genotypes, grown under control conditions (grey bars, offspring environment ‘C’) and nutrient stress (open bars, offspring environment ‘N’) (means ± SEM). See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038605#pone-0038605-t002" target="_blank">Table 2</a> for p-values.</p

Experiment 1: design and results of <i>Spodoptera exigua</i> choice feeding assays.

<p>Inset picture: J, offspring of JA-treated plant; C, offspring of control plant. Inset table shows for each independent trial if more tissue was consumed from JA-offspring or from control-offspring leaf discs.</p

Experiment 2: effects of parental nutrient stress on offspring traits in three apomictic genotypes.

1<p>log-transformed prior to analysis to meet ANOVA requirements.</p><p>ANOVA test results are shown for all model factors; factors of special interest are those that include parental nutrient treatment (nutrient_parent). Error degrees of freedom = 66, model term degrees of freedom are in parentheses.</p