Cadmium (Cd), a common environmental toxic contaminant, is easily accumulated in living organisms, leading to numerous harmful effects. Chlamydomonas reinhardtii, a unicellular eukaryotic green algae strain, is a very suitable candidate for bioremediation of Cd-contaminated water. However, for the poor resistance to Cd, application of C. reinhardtii was restricted and genes mediating Cd tolerance in C. reinhardtii remain unclear. In this paper, adaptive laboratory evolution was performed with algae constant exposure to Cd over 420-day at environmentally relevant concentrations to select C. reinhardtii strains with high tolerance to Cd. Physiological indicators, such as cell proliferation, photosynthetic pigment contents and photosynthetic activity of photosystem were detected to evaluate the Cd tolerance of selected algae strain ALE0.5. Then, whole-genome re-sequencing and transcriptome were applied to identify the genes related to Cd tolerance. Genes involved in photosynthesis (PSBP1), glutathione metabolism (CHLREDRAFT_167073, GPX5) and calcium transport (CHLREDRAFT_189266, CHLREDRAFT_191203, CHLREDRAFT_187187, CSE1) were related to Cd tolerance in C. reinhardtii. This study provides a basis for obtaining transgenic C. reinhardtii strains with high Cd tolerance used for bioremediation of Cd pollution in the future.

中文翻译：

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全基因组重测序和转录组揭示了莱茵衣藻中与镉耐受性相关的基因和途径。

镉（Cd）是一种常见的环境有毒污染物，很容易在生物体内积累，导致许多有害影响。莱茵衣藻（Chlamydomonas reinhardtii）是一种单细胞真核绿藻菌株，非常适合用于镉污染水的生物修复。但是，由于对Cd的抵抗力较弱，因此对Reinhardtii的应用受到限制，而在Reinhardtii中介导Cd耐受性的基因仍不清楚。在本文中，在环境相关浓度下，藻类在420天中持续暴露于Cd的条件下，进行了适应性实验室进化，以选择对Cd具有高耐受性的莱茵衣藻C. reinhardtii菌株。检测细胞增殖，光合色素含量和光合系统的光合活性等生理指标，以评价所选藻类ALE0.5对Cd的耐受性。然后，使用全基因组重测序和转录组来鉴定与Cd耐受性相关的基因。参与光合作用的基因（PSBP1），谷胱甘肽代谢（CHLREDRAFT_167073，GPX5）和钙转运（CHLREDRAFT_189266，CHLREDRAFT_191203，CHLREDRAFT_187187，CSE1）与雷氏梭菌对Cd的耐受性有关。该研究为将来获得具有高镉耐受性的转基因雷氏梭菌菌株用于生物修复镉污染提供了基础。