Centre for Sustainable Ecosystem Solutions, School of Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW, 2522, Australia.
Department of Chemistry and Biology, University of Santiago, Alameda, 3363, Santiago, Chile.
Biol Res. 2018 Nov 21;51(1):49. doi: 10.1186/s40659-018-0196-1.
Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica.
Multiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory.
UVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.
南极苔藓植物（苔藓和地钱）对生理极端环境条件具有很强的适应能力，包括由于平流层臭氧消耗而导致的高水平紫外线（UV）辐射。许多南极苔藓植物合成 UV-B 吸收化合物（UVAC），这些化合物位于其细胞和细胞壁内，而植物中很少研究这些位置的 UVAC。本研究比较了来自东南极风车群岛的南极 Ceratodon purpureus、Bryum pseudotriquetrum 和 Schistidium antarctici 中细胞内和细胞壁内 UVAC 的浓度和定位。
多种胁迫因素，包括干燥和自然存在的高 UV 和可见光，似乎增强了所有三种南极物种细胞壁中总 UVAC 的掺入，包括红色色素。C. purpureus 的红色生长形式具有明显更高水平的细胞壁结合和更低的细胞内 UVAC 浓度，而其附近的绿色形式则具有更低的细胞壁结合和更高的细胞内 UVAC 浓度。显微镜和光谱分析表明，该物种的红色着色与细胞壁有关，并且这些红色细胞壁比绿色形式含有更少的果胶和酚酯。所有三种苔藓物种在生长季节中细胞壁 UVAC 含量自然增加，而在实验室中在压力较小的条件下生长的新组织中这些化合物含量下降。
UVAC 和红色色素紧密结合在细胞壁上，可能在南极苔藓植物中具有长期的保护作用。尽管这些红色色素的身份仍然未知，但我们的研究表明，在植物中研究细胞壁 UVAC 的重要性，并有助于我们当前对特定南极苔藓植物使用的 UV 保护策略的理解。此类研究为这些植物如何在如此极端的栖息地中生存提供了线索，并有助于预测所研究物种的未来生存。
