Laboratorio de Fisiología Vegetal, Centro de Estudios Avanzados en Zonas Áridas CEAZA, La Serena, Chile.
Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile.
BMC Plant Biol. 2020 Feb 4;20(1):56. doi: 10.1186/s12870-019-2182-3.
Filmy-ferns (Hymenophyllaceae) are poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphytes. They can colonize lower and upper canopy environments of humid forest. Filmy-ferns desiccate rapidly (hours), contrasting with DT angiosperms (days/weeks). It has been proposed that desiccation tolerance in filmy-ferns would be associated mainly with constitutive features rather than induced responses during dehydration. However, we hypothesize that the inter-specific differences in vertical distribution would be associated with different dynamics of gene expression within the dehydration or rehydration phases. A comparative transcriptomic analysis with an artificial neural network was done on Hymenophyllum caudiculatum (restricted to lower canopy) and Hymenophyllum dentatum (reach upper canopy) during a desiccation/rehydration cycle.
Raw reads were assembled into 69,599 transcripts for H. dentatum and 34,726 transcripts for H. caudiculatum. Few transcripts showed significant changes in differential expression (DE). H. caudiculatum had ca. twice DE genes than H. dentatum and higher proportion of increased-and-decreased abundance of genes occurs during dehydration. In contrast, the abundance of genes in H. dentatum decreased significantly when transitioning from dehydration to rehydration. According to the artificial neural network results, H. caudiculatum enhanced osmotic responses and phenylpropanoid related pathways, whilst H. dentatum enhanced its defense system responses and protection against high light stress.
Our findings provide a deeper understanding of the mechanisms underlying the desiccation tolerance responses of two filmy ferns and the relationship between the species-specific response and the microhabitats these ferns occupy in nature.
膜蕨（膜蕨科）是具有异形叶性、同型叶绿素、耐旱（DT）的附生植物。它们可以在潮湿森林的下层和上层冠层环境中定殖。膜蕨可以迅速（数小时）脱水，与 DT 被子植物（数天/数周）形成对比。有人提出，膜蕨的耐旱性主要与组成性特征有关，而不是与脱水过程中的诱导反应有关。然而，我们假设，垂直分布的种间差异与脱水或复水阶段内基因表达的不同动态有关。我们对仅限于下层冠层的膜蕨（Hymenophyllum caudiculatum）和可到达上层冠层的膜蕨（Hymenophyllum dentatum）进行了一个脱水/复水周期的比较转录组分析，并结合人工神经网络进行分析。
原始读数被组装成 69599 个转录本用于 H. dentatum 和 34726 个转录本用于 H. caudiculatum。少数转录本显示出明显的差异表达（DE）变化。H. caudiculatum 的 DE 基因数量约为 H. dentatum 的两倍，并且在脱水过程中增加和减少的基因丰度比例更高。相比之下，当从脱水过渡到复水时，H. dentatum 的基因丰度显著下降。根据人工神经网络的结果，H. caudiculatum 增强了渗透响应和苯丙烷相关途径，而 H. dentatum 增强了其防御系统反应和对高光胁迫的保护。
我们的研究结果提供了对两种膜蕨耐旱性反应的机制以及这些蕨类植物在自然界中特定物种反应与其微生境之间的关系的更深入了解。
