Diretoria de Pesquisa Científica, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brasil.
PLoS One. 2010 Apr 26;5(4):e10326. doi: 10.1371/journal.pone.0010326.
Epigenetic modifications, such as cytosine methylation, are inherited in plant species and may occur in response to biotic or abiotic stress, affecting gene expression without changing genome sequence. Laguncularia racemosa, a mangrove species, occurs in naturally contrasting habitats where it is subjected daily to salinity and nutrient variations leading to morphological differences. This work aims at unraveling how CpG-methylation variation is distributed among individuals from two nearby habitats, at a riverside (RS) or near a salt marsh (SM), with different environmental pressures and how this variation is correlated with the observed morphological variation.
Significant differences were observed in morphological traits such as tree height, tree diameter, leaf width and leaf area between plants from RS and SM locations, resulting in smaller plants and smaller leaf size in SM plants. Methyl-Sensitive Amplified Polymorphism (MSAP) was used to assess genetic and epigenetic (CpG-methylation) variation in L. racemosa genomes from these populations. SM plants were hypomethylated (14.6% of loci had methylated samples) in comparison to RS (32.1% of loci had methylated samples). Within-population diversity was significantly greater for epigenetic than genetic data in both locations, but SM also had less epigenetic diversity than RS. Frequency-based (G(ST)) and multivariate (beta(ST)) methods that estimate population structure showed significantly greater differentiation among locations for epigenetic than genetic data. Co-Inertia analysis, exploring jointly the genetic and epigenetic data, showed that individuals with similar genetic profiles presented divergent epigenetic profiles that were characteristic of the population in a particular environment, suggesting that CpG-methylation changes may be associated with environmental heterogeneity.
In spite of significant morphological dissimilarities, individuals of L. racemosa from salt marsh and riverside presented little genetic but abundant DNA methylation differentiation, suggesting that epigenetic variation in natural plant populations has an important role in helping individuals to cope with different environments.
表观遗传修饰，如胞嘧啶甲基化，在植物物种中是可遗传的，并且可能响应生物或非生物胁迫而发生，从而在不改变基因组序列的情况下影响基因表达。白骨壤是一种红树林物种，存在于自然条件差异很大的生境中，其每天都受到盐度和养分变化的影响，导致形态差异。这项工作旨在揭示来自两个附近生境（河边（RS）或盐沼附近（SM））的个体中 CpG 甲基化变异如何分布，这些个体处于不同的环境压力下，以及这种变异如何与观察到的形态变异相关。
RS 和 SM 位置的植物在形态特征上存在显著差异，如树高、树径、叶宽和叶面积，导致 SM 植物的植株较小，叶片较小。使用甲基敏感扩增多态性（MSAP）评估来自这些种群的白骨壤基因组的遗传和表观遗传（CpG 甲基化）变异。与 RS（32.1%的位点有甲基化样本）相比，SM 植物的甲基化程度较低（14.6%的位点有甲基化样本）。在两个位置，基于频率的（G(ST)）和多元的（beta(ST)）方法估计种群结构，都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。基于频率的（G(ST)）和多元的（beta(ST)）方法估计种群结构，都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。频率（G(ST)）和多元（beta(ST)）方法估计种群结构，在两个位置都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。频率（G(ST)）和多元（beta(ST)）方法估计种群结构，在两个位置都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。频率（G(ST)）和多元（beta(ST)）方法估计种群结构，在两个位置都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。频率（G(ST)）和多元（beta(ST)）方法估计种群结构，都显示出表观遗传数据比遗传数据具有更高的种群内多样性，但 SM 的表观遗传多样性也比 RS 低。
尽管形态差异显著，但来自盐沼和河边的白骨壤个体的遗传差异很小，但 DNA 甲基化差异很大，这表明自然植物种群中的表观遗传变异在帮助个体应对不同环境方面起着重要作用。
