National Laboratory of Genomics for Biodiversity (Langebio), Unit of Advanced Genomics, CINVESTAV, 36824, Irapuato, Guanajuato, Mexico.
Department of Genetic Engineering, CINVESTAV, 36824, Irapuato, Guanajuato, Mexico.
BMC Plant Biol. 2020 Oct 12;20(1):468. doi: 10.1186/s12870-020-02638-3.
Desiccation tolerant Selaginella species evolved to survive extreme environmental conditions. Studies to determine the mechanisms involved in the acquisition of desiccation tolerance (DT) have focused on only a few Selaginella species. Due to the large diversity in morphology and the wide range of responses to desiccation within the genus, the understanding of the molecular basis of DT in Selaginella species is still limited.
Here we present a reference transcriptome for the desiccation tolerant species S. sellowii and the desiccation sensitive species S. denticulata. The analysis also included transcriptome data for the well-studied S. lepidophylla (desiccation tolerant), in order to identify DT mechanisms that are independent of morphological adaptations. We used a comparative approach to discriminate between DT responses and the common water loss response in Selaginella species. Predicted proteomes show strong homology, but most of the desiccation responsive genes differ between species. Despite such differences, functional analysis revealed that tolerant species with different morphologies employ similar mechanisms to survive desiccation. Significant functions involved in DT and shared by both tolerant species included induction of antioxidant systems, amino acid and secondary metabolism, whereas species-specific responses included cell wall modification and carbohydrate metabolism.
Reference transcriptomes generated in this work represent a valuable resource to study Selaginella biology and plant evolution in relation to DT. Our results provide evidence of convergent evolution of S. sellowii and S. lepidophylla due to the different gene sets that underwent selection to acquire DT.
耐旱的卷柏属物种进化以适应极端环境条件。为了确定获得耐旱性（DT）所涉及的机制而进行的研究仅集中在少数几种卷柏属物种上。由于形态多样性和属内对干燥的响应范围广泛，因此对卷柏属物种中 DT 的分子基础的理解仍然有限。
我们在这里为耐旱物种 S. sellowii 和耐旱敏感物种 S. denticulata 提供了参考转录组。该分析还包括形态学研究较为充分的 S. lepidophylla 的转录组数据，以鉴定与形态适应无关的 DT 机制。我们使用了一种比较方法来区分卷柏属物种中的 DT 响应与常见的失水响应。预测的蛋白质组具有很强的同源性，但大多数耐旱响应基因在物种之间存在差异。尽管存在这些差异，但功能分析表明，具有不同形态的耐旱物种采用相似的机制来在干燥中存活。与两者都耐旱的物种有关的重要功能包括诱导抗氧化系统、氨基酸和次生代谢，而物种特异性反应包括细胞壁修饰和碳水化合物代谢。
本研究生成的参考转录组代表了研究与 DT 相关的卷柏生物学和植物进化的有价值的资源。我们的结果提供了证据，表明 S. sellowii 和 S. lepidophylla 由于不同的基因集经过选择以获得 DT 而表现出趋同进化。
