PDF(Pubmed)
Abstract：
Lichens are symbiotic organisms that effectively survive in harsh environments, including arid regions. Maintaining viability with an almost complete loss of water and the rapid restoration of metabolism during rehydration distinguishes lichens from most eukaryotic organisms. The lichen Xanthoria parietina is known to have high stress tolerance, possessing diverse defense mechanisms, including the presence of the bright-orange pigment parietin. While several studies have demonstrated the photoprotective and antioxidant properties of this anthraquinone, the role of parietin in the tolerance of lichens to desiccation is not clear yet. Thalli, which are exposed to solar radiation and become bright orange, may require enhanced desiccation tolerance. Here, we showed differences in the anatomy of naturally pale and bright-orange thalli of X. parietina and visualized parietin crystals on the surface of the upper cortex. Parietin was extracted from bright-orange thalli by acetone rinsing and quantified using HPLC. Although acetone rinsing did not affect PSII activity, thalli without parietin had higher levels of lipid peroxidation and a lower membrane stability index in response to desiccation. Furthermore, highly pigmented thalli possess thicker cell walls and, according to thermogravimetric analysis, higher water-holding capacities than pale thalli. Thus, parietin may play a role in desiccation tolerance by stabilizing mycobiont membranes, providing an antioxidative defense, and changing the morphology of the upper cortex of X. parietina.
摘要：
地衣是在恶劣环境中有效生存的共生生物，包括干旱地区。保持生存力，几乎完全失去水分，并在补液过程中迅速恢复新陈代谢，使地衣与大多数真核生物区分开来。众所周知，地衣Xanthoriaparietina具有很高的抗逆性，拥有多样化的防御机制，包括亮橙色色素parietin的存在。虽然一些研究已经证明了这种蒽醌的光保护和抗氧化特性，parietin在地衣对干燥的耐受性中的作用尚不清楚。Thalli,它们暴露在太阳辐射下，变成亮橙色，可能需要增强的干燥耐受性。这里,我们显示了X的自然苍白和亮橙色thalli的解剖结构差异。parietina和上皮层表面的可视化parietin晶体。通过丙酮冲洗从亮橙色thalli中提取Parietin，并使用HPLC进行定量。尽管丙酮冲洗不影响PSII活性，不含parietin的thalli对干燥的反应具有较高的脂质过氧化水平和较低的膜稳定性指数。此外，高度色素沉着的Thalli具有较厚的细胞壁，根据热重分析,比苍白的塔利更高的持水能力。因此，parietin可能通过稳定分枝杆菌膜在干燥耐受性中发挥作用，提供抗氧化防御，并改变了X.Parietina上皮质的形态。
