Institute of Botany, Faculty of Biology, Jagiellonian University, Gronostajowa 3, 30-387, Kraków, Poland.
Laboratory of Metabolomics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland.
Chemosphere. 2022 Dec;308(Pt 2):136365. doi: 10.1016/j.chemosphere.2022.136365. Epub 2022 Sep 7.
Heavy metals present in the environment can cause a variety of injury symptoms in various organisms including lichens. Most studies examined metal-induced stress under controlled laboratory conditions, and little is known about actual response of lichens in their natural habitat. This study aims to recognize the effect of heavy metal accumulation (total and intracellular) on lichen physiological and biochemical parameters specifically related to the functioning of fungal component. Cladonia rei was used as a model species due to its common occurrence both in unpolluted and extremely polluted sites. We observed a decline in the fungal metabolism which was expressed by a decrease in ergosterol content and an increase in cell membrane damage as a result of increased Zn, Cd, Cu and Ni accumulation. Additionally, the results indicated that increased accumulation of xenobiotics (Pb and As) caused reduction of glutathione (GSH) concentrations and increased membrane lipid peroxidation. Therefore, we conclude that GSH does not provide high oxidative stress protection in C. rei which is somewhat against its insensitivity to pollution. The reduced pool of GSH could be explained by its oxidation to glutathione disulphide induced by heavy metal stress or its use for phytochelatin (PC) synthesis. The content of secondary metabolites was not related to heavy metal accumulation and remained at a relatively stable level. This indicates that the decline in the physiological condition did not weaken the mycobiont of C. rei enough to inhibit the synthesis of secondary metabolites and their precursors were supplied at a sufficient level. Thus, the potential function of main secondary metabolites as extracellular metal immobilizers and antioxidants is still possible even in individuals growing at extremely polluted sites. Despite the evident heavy metal stress, C. rei copes well and spreads easily through extremely polluted environments, which underlines its unique pioneering abilities in highly disturbed sites.
环境中的重金属会对包括地衣在内的各种生物体造成多种伤害症状。大多数研究都是在受控实验室条件下检查金属诱导的应激反应，而对于地衣在其自然栖息地的实际反应知之甚少。本研究旨在认识重金属积累（总量和细胞内）对与真菌成分功能特别相关的地衣生理生化参数的影响。克莱多尼亚 rei 被用作模型物种，因为它在未污染和极度污染的地点都很常见。我们观察到真菌代谢的下降，这表现为麦角固醇含量的减少和细胞膜损伤的增加，这是由于 Zn、Cd、Cu 和 Ni 积累的增加。此外，结果表明，外源污染物（Pb 和 As）的积累增加导致谷胱甘肽 (GSH) 浓度降低和膜脂质过氧化增加。因此，我们得出结论，GSH 在地衣 rei 中不能提供高氧化应激保护，这与它对污染的不敏感性有些矛盾。GSH 减少的原因可能是由于重金属胁迫诱导的 GSH 氧化为二硫化物，或者是由于其用于合成植物螯合肽 (PC)。次生代谢物的含量与重金属积累无关，保持在相对稳定的水平。这表明生理状况的下降并没有削弱 C. rei 的地衣共生体，不足以抑制次生代谢物的合成，并且它们的前体以足够的水平供应。因此，即使在地衣生长在极度污染的地方，主要次生代谢物作为细胞外金属固定剂和抗氧化剂的潜在功能仍然是可能的。尽管存在明显的重金属胁迫，但 C. rei 仍能很好地应对，并容易在极度污染的环境中传播，这突显了它在高度干扰的地点具有独特的开拓能力。
