Brine shrimp Artemia have an unequalled ability to endure extreme salinity and complete anoxia. This study aims to elucidate its strategies to cope with these stressors. Here, we present the genome of an inbred A. franciscana Kellogg, 1906. We identified 21,828 genes of which, under high salinity, 674 genes and under anoxia, 900 genes were differentially expressed (42%, respectively 30% were annotated). Under high salinity, relevant stress genes and pathways included several Heat Shock Protein and Leaf Embryogenesis Abundant genes, as well as the trehalose metabolism. In addition, based on differential gene expression analysis, it can be hypothesized that a high oxidative stress response and endocytosis/exocytosis are potential salt management strategies, in addition to the expression of major facilitator superfamily genes responsible for transmembrane ion transport. Under anoxia, genes involved in mitochondrial function, mTOR signalling and autophagy were differentially expressed. Both high salt and anoxia enhanced degradation of erroneous proteins and protein chaperoning. Compared with other branchiopod genomes, Artemia had 0.03% contracted and 6% expanded orthogroups, in which 14% of the genes were differentially expressed under high salinity or anoxia. One phospholipase D gene family, shown to be important in plant stress response, was uniquely present in both extremophiles Artemia and the tardigrade Hypsibius dujardini, yet not differentially expressed under the described experimental conditions. A relatively complete genome of Artemia was assembled, annotated and analysed, facilitating research on its extremophile features, and providing a reference sequence for crustacean research.

中文翻译：

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极端微生物卤虫的基因组为应对极端环境的策略提供了见解

丰年虾具有无与伦比的忍受极端盐度和完全缺氧的能力。这项研究旨在阐明其应对这些压力源的策略。在这里，我们展示了 1906 年近交的 A. franciscana Kellogg 的基因组。我们鉴定了 21,828 个基因，其中在高盐度下有 674 个基因，在缺氧下有 900 个基因有差异表达（分别有 42% 和 30% 被注释）。高盐度下，相关的胁迫基因和途径包括多个热休克蛋白和叶胚胎发生丰富基因，以及海藻糖代谢。此外，基于差异基因表达分析，可以假设，除了负责跨膜离子转运的主要促进超家族基因的表达之外，高氧化应激反应和胞吞作用/胞吐作用是潜在的盐管理策略。在缺氧条件下，涉及线粒体功能、mTOR信号传导和自噬的基因出现差异表达。高盐和缺氧都会增强错误蛋白质的降解和蛋白质陪伴。与其他鳃足类基因组相比，卤虫的原位群收缩了0.03%，扩张了6%，其中14%的基因在高盐或缺氧条件下出现差异表达。一个磷脂酶 D 基因家族被证明在植物胁迫反应中很重要，它独特地存在于极端微生物卤虫和缓步动物 Hypsibius dujardini 中，但在所描述的实验条件下没有差异表达。组装、注释和分析了较为完整的卤虫基因组，有利于对其极端微生物特征的研究，为甲壳类研究提供参考序列。