Elder Charles A, Skaggs Hannah M, Dirk Lynnette M A, Grimm David F, Belott Clinton J, Wolkers Willem F, Oldenhof Harriëtte, Uversky Vladimir N, Downie A Bruce, Menze Michael A
Department of Biology, University of Louisville, Louisville, Kentucky, USA.
Seed Biology Group, Department of Horticulture, Martin-Gatton College of Agriculture, Food and Environment, University of Kentucky, Lexington, Kentucky, USA.
Protein Sci. 2025 Jul;34(7):e70192. doi: 10.1002/pro.70192.
It is often underappreciated that despite water being a requirement for life on Earth, organisms belonging to all taxonomic kingdoms have developed mechanisms to survive desiccation. These organisms, referred to as anhydrobiotes, accumulate specific biomolecules during or before drying that facilitate the survival of desiccation stress. Compounds utilized by a wide variety of anhydrobiotes during desiccation include metabolites such as sugars and amino acids, as well as proteins with extensive intrinsically disordered regions. Intrinsically disordered proteins that are constitutively expressed or upregulated during the onset or in preparation for desiccation include late embryogenesis abundant proteins, tardigrade disordered proteins, hydrophilins, some small heat shock proteins, and prion-like proteins. Some of these proteins form biomolecular condensates in the cellular environment. We hypothesize that phase transitions driven by anhydrobiosis-related intrinsically disordered proteins play a substantial role in enabling anhydrobiosis by (1) contributing to the downregulation of metabolic and developmental processes, (2) selectively sequestering desiccation-sensitive molecules into a "protective compartment" during drying, (3) interfering with programmed cell death signaling pathways to confer optimal time for the cell to repair after rehydration, (4) resisting intracellular volume changes to aid in membrane stabilization during desiccation, and (5) changing the biophysical properties of water to reduce desiccation-induced cellular damage. Biochemical strategies in anhydrobiotes are certainly multifaceted and may differ among systems. Nevertheless, a better understanding of the relevance of phase transitions in anhydrobiosis may allow us to get one step closer to unraveling the enigmatic phenomenon of life without water.
人们常常没有充分认识到，尽管水是地球上生命的必需品，但所有生物分类界的生物都已经进化出了在干燥环境中生存的机制。这些生物被称为脱水生物，它们在干燥过程中或干燥之前积累特定的生物分子，以促进在脱水胁迫下的生存。各种各样的脱水生物在脱水过程中利用的化合物包括糖类和氨基酸等代谢物，以及具有广泛内在无序区域的蛋白质。在脱水开始时或为脱水做准备时组成型表达或上调的内在无序蛋白质包括晚期胚胎发生丰富蛋白、缓步动物无序蛋白、亲水性蛋白、一些小分子热休克蛋白和朊病毒样蛋白。其中一些蛋白质在细胞环境中形成生物分子凝聚物。我们假设，由与脱水生物相关的内在无序蛋白质驱动的相变在实现脱水生物生存中起着重要作用，具体方式如下：（1）有助于下调代谢和发育过程；（2）在干燥过程中选择性地将对脱水敏感的分子隔离到一个“保护隔室”中；（3）干扰程序性细胞死亡信号通路，为细胞在复水后修复提供最佳时间；（4）抵抗细胞内体积变化，以帮助在脱水过程中稳定膜；（5）改变水的生物物理性质，以减少脱水引起的细胞损伤。脱水生物中的生化策略肯定是多方面的，而且不同系统之间可能有所不同。然而，更好地理解相变在脱水生物中的相关性，可能会让我们离解开无水生命这一神秘现象更近一步。
