Protopopova Marina V, Pavlichenko Vasiliy V, Menzel Ralph, Putschew Anke, Luckenbach Till, Steinberg Christian E W
Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch Russian Academy of Sciences, Lermontov str., 132, Irkutsk, Russia, 664033,
Environ Sci Pollut Res Int. 2014 Dec;21(24):14124-37. doi: 10.1007/s11356-014-3323-8. Epub 2014 Jul 23.
The species-rich, endemic amphipod fauna of Lake Baikal does not overlap with the common Palearctic fauna; however, the underlying mechanisms for this are poorly understood. Considering that Palearctic lakes have a higher relative input of natural organic compounds with a dominance of humic substances (HSs) than Lake Baikal, we addressed the question whether HSs are candidate factors that affect the different species compositions in these water bodies. We hypothesized that interspecies differences in stress defense might reveal that Baikalian amphipods are inferior to Palearctic amphipods in dealing with HS-mediated stress. In this study, two key mechanisms of general stress response were examined: heat-shock protein 70 (HSP70) and multixenobiotic resistance-associated transporters (ABCB1). The results of quantitative polymerase chain reaction (qPCR) showed that the basal levels (in 3-day acclimated animals) of hsp70 and abcb1 transcripts were lower in Baikalian species (Eulimnogammarus cyaneus, Eulimnogammarus verrucosus, Eulimnogammarus vittatus-the most typical littoral species) than in the Palearctic amphipod (Gammarus lacustris-the only Palearctic species distributed in the Baikalian region). In the amphipods, the stress response was induced using HSs at 10 mg L(-1) dissolved organic carbon, which was higher than in sampling sites of the studied species, but well within the range (3-10 mg L(-1)) in the surrounding water bodies populated by G. lacustris. The results of qPCR and western blotting (n = 5) showed that HS exposure led to increased hsp70/abcb1 transcripts and HSP70 protein levels in G. lacustris, whereas these transcript levels remained constant or decreased in the Baikalian species. The decreased level of stress transcripts is probably not able to confer an effective tolerance to Baikalian species against further environmental stressors in conditions with elevated HS levels. Thus, our results suggest a greater robustness of Palearctic amphipods and a higher sensitivity of Baikalian amphipods to HS challenge, which might prevent most endemic species from migrating to habitats outside Lake Baikal.
贝加尔湖物种丰富的特有双壳类动物区系与古北区常见动物区系并不重叠；然而，其背后的机制却鲜为人知。鉴于古北区湖泊中天然有机化合物的相对输入量较高，且腐殖质占主导地位，而贝加尔湖则不然，我们提出了一个问题：腐殖质是否是影响这些水体中不同物种组成的候选因素。我们推测，应激防御方面的种间差异可能表明，贝加尔湖双壳类动物在应对腐殖质介导的应激方面不如古北区双壳类动物。在本研究中，我们考察了一般应激反应的两个关键机制：热休克蛋白70（HSP70）和多异生物质抗性相关转运蛋白（ABCB1）。定量聚合酶链反应（qPCR）结果表明，贝加尔湖物种（蓝湖钩虾、瘤湖钩虾、带纹湖钩虾——最典型的沿岸物种）中hsp70和abcb1转录本的基础水平（在适应3天的动物中）低于古北区双壳类动物（湖沼钩虾——分布在贝加尔湖地区的唯一古北区物种）。在双壳类动物中，使用溶解有机碳含量为10 mg L(-1)的腐殖质诱导应激反应，该含量高于所研究物种的采样点，但仍在湖沼钩虾所在周边水体的范围内（3-10 mg L(-1)）。qPCR和蛋白质免疫印迹（n = 5）结果表明，腐殖质暴露导致湖沼钩虾中hsp70/abcb1转录本和HSP70蛋白水平升高，而贝加尔湖物种中的这些转录本水平保持不变或下降。应激转录本水平的降低可能无法使贝加尔湖物种在腐殖质水平升高的条件下有效耐受进一步的环境应激源。因此，我们的结果表明，古北区双壳类动物具有更强的稳健性，而贝加尔湖双壳类动物对腐殖质挑战更为敏感，这可能会阻止大多数特有物种迁移到贝加尔湖以外的栖息地。
