Aloe vera is a species from Asphodelaceae plant family having unique characteristics such as drought resistance and also possesses numerous medicinal properties. However, the genetic basis of these phenotypes is yet unknown, primarily due to the unavailability of its genome sequence. In this study, we report the first Aloe vera draft genome sequence comprising of 13.83 Gbp and harboring 86,177 coding genes. It is also the first genome from the Asphodelaceae plant family and is the largest angiosperm genome sequenced and assembled till date. Further, we report the first genome-wide phylogeny of monocots with Aloe vera using 1,440 one-to-one orthologs that resolves the genome-wide phylogenetic position of Aloe vera with respect to the other monocots. The comprehensive comparative analysis of Aloe vera genome with the other available high-quality monocot genomes revealed adaptive evolution in several genes of the drought stress response, CAM pathway, and circadian rhythm in Aloe vera. Further, genes involved in DNA damage response, a key pathway in several biotic and abiotic stress response mechanisms, were found to be positively selected. This provides the genetic basis of the evolution of drought stress tolerance capabilities of Aloe vera. This also substantiates the previously suggested notion that the evolution of unique characters in this species is perhaps due to selection and adaptive evolution rather than the phylogenetic divergence or isolation.

中文翻译：

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芦荟的基因组序列揭示了抗旱机制的适应性进化

芦荟（Aloe vera）是来自水草科植物家族的物种，具有诸如抗旱性的独特特征，并且还具有许多药用特性。然而，这些表型的遗传基础仍是未知的，主要是由于其基因组序列的缺乏。在这项研究中，我们报告了包括13.83 Gbp的86.177个编码基因的第一条芦荟基因组序列。它也是来自Asphodelaceae植物家族的第一个基因组，并且是迄今为止测序和组装的最大的被子植物基因组。此外，我们报告了使用1,440个一对一直向同源物，与芦荟有关的单子叶植物的第一个全基因组系统发育史，它解决了芦荟相对于其他单子叶植物的全基因组系统发育地位。芦荟基因组与其他可用的高质量单子叶植物基因组的综合比较分析显示，芦荟中干旱胁迫响应，CAM途径和昼夜节律的几个基因具有适应性进化。此外，发现积极选择了涉及DNA损伤反应的基因，DNA损伤反应是几种生物和非生物应激反应机制中的关键途径。这为芦荟抗旱能力的进化提供了遗传基础。这也证实了先前提出的观念，即该物种独特性状的进化可能是由于选择和适应性进化，而不是系统发育的分歧或隔离。此外，发现积极选择了涉及DNA损伤反应的基因，DNA损伤反应是几种生物和非生物应激反应机制中的关键途径。这为芦荟抗旱能力的进化提供了遗传基础。这也证实了先前提出的观念，即该物种独特性状的进化可能是由于选择和适应性进化，而不是系统发育的分歧或隔离。此外，发现积极选择了涉及DNA损伤反应的基因，DNA损伤反应是几种生物和非生物应激反应机制中的关键途径。这为芦荟抗旱能力的进化提供了遗传基础。这也证实了先前提出的观念，即该物种独特性状的进化可能是由于选择和适应性进化，而不是系统发育的分歧或隔离。