Data from: Adaptive differences in gene expression associated with heavy metal tolerance in the soil arthropod Orchesella cincta

Field-selected tolerance to heavy metals has been reported for Orchesella cincta (Arthropoda: Collembola) populations occurring at metal-contaminated mining sites. This tolerance is correlated with heritable increase of metal excretion efficiency; less pronounced cadmium (Cd) induced growth reduction and, over-expression of the metallothionein gene. We applied transcriptomics to determine differential gene expression caused by this abiotic stress in reference and Cd tolerant populations. Many cDNAs responded to Cd exposure in the reference population. Significantly fewer clones were Cd responsive in tolerant animals. Analysis of variance revealed transcripts that interact between Cd exposure and population. Hierarchical cluster analysis of these clones identified two major groups. The first one contained cDNAs that were up regulated by Cd in the reference culture, but non-responsive or down regulated in tolerant animals. This cluster was also characterized by elevated constitutive expression in the tolerant population. Gene ontology analysis revealed that these cDNAs were involved in structural integrity of the cuticle, anti-microbial defense, calcium-channel blocking, sulfur assimilation and chromatin remodeling. The second group consisted of cDNAs down regulated in reference animals but not responding or slightly up regulated in tolerant animals. Their functions involved carbohydrate metabolic processes, Ca2+ dependent stress signaling, redox state, proteolysis and digestion. The reference population showed a strong signature of stress-induced genome-wide perturbation of gene expression, whereas the tolerant animals maintained normal gene expression upon Cd exposure. We confirmed the micro-evolutionary processes occurring in soil arthropod populations and suggest a major contribution of gene regulation to the evolution of a stress-adapted phenotype.

已有研究报道，栖息于重金属污染矿区的带角长跳虫（Orchesella cincta，节肢动物门：弹尾纲）种群具备经野外自然筛选获得的重金属耐受性。该耐受性与金属排泄效率的可遗传提升、镉（Cd）诱导的生长抑制效应减弱以及金属硫蛋白基因的过表达显著相关。本研究利用转录组学技术，探究参考种群与镉耐受种群在该非生物胁迫下的差异基因表达情况。参考种群中，大量互补DNA（cDNA）会在镉暴露下出现表达响应；而耐受种群中对镉产生响应的克隆数量显著更少。方差分析筛选出了与镉暴露和种群类型存在交互作用的转录本。对这些克隆进行层级聚类分析后，得到两个主要的基因簇。第一个基因簇包含的cDNA在参考种群中会因镉暴露而上调，但在耐受种群中无表达响应或表达量下调；该基因簇同时表现为耐受种群中组成型表达水平升高的特征。基因本体（Gene Ontology, GO）注释分析显示，这些cDNA参与的生物学过程包括角质层结构完整性维持、抗菌防御、钙通道阻滞、硫同化以及染色质重塑。第二个基因簇包含的cDNA在参考种群中会因镉暴露而下调，但在耐受种群中无表达响应或仅出现轻微上调；这些cDNA所参与的生物学过程包括碳水化合物代谢、钙离子依赖型胁迫信号通路、氧化还原稳态调控、蛋白水解以及消化功能。参考种群呈现出胁迫诱导的全基因组基因表达紊乱的显著特征，而耐受种群在镉暴露下仍能维持正常的基因表达水平。本研究证实了土壤节肢动物种群中存在的微进化过程，并提出基因调控在胁迫适应表型的进化过程中发挥了重要作用。