Department of Biology, McGill University, Montréal, Québec H3A 1B1, Canada.
Metallomics. 2020 Jul 22;12(7):1106-1117. doi: 10.1039/d0mt00033g.
Copper (Cu) is an essential cofactor of photosynthetic and respiratory redox proteins in phytoplankton and a scarce resource in parts of the open sea. Although its importance for growth is well recognized, the molecular mechanisms by which phytoplankton respond and acclimate to Cu deficiency are not well known. In this study, we identified the dominant Cu-regulated proteins and measured key physiological traits of Thalassiosira oceanica (CCMP 1005) under Cu-limiting and sufficient conditions. Growth limitation of T. oceanica occurred at environmentally relevant Cu concentrations (1 nM) as a result of decreased photosynthetic efficiency (ΦPSII). In Cu-limited cells, levels of plastocyanin decreased by 3-fold compared to Cu-replete cells and rates of maximum photosynthetic electron transport were reduced. Proteins associated with light harvesting complexes also declined in response to Cu limitation, presumably to adjust to reduced photosynthetic electron flow and to avoid photodamage to the photosystems. Key enzymes involved in carbon and nitrogen assimilation were down-regulated in low-Cu cells, as were steady state rates of C and N uptake. Relatively fewer proteins were up-regulated by Cu limitation, but among them were two enzymes involved in fatty acid oxidation (FAO). The increase in FAO may be a sign of increased turnover of cellular lipids caused by damage from oxidative stress. A putative transcription factor containing three, repetitive methionine motifs (MpgMgggM; MpgMggM) increased significantly in Cu-limited cells. The collective results provide a general description of how plastocyanin-dependent diatoms adjust metabolism to cope with chronic Cu deficiency.
铜 (Cu) 是浮游植物光合作用和呼吸氧化还原蛋白的必需辅因子，也是开阔海域部分地区的稀缺资源。尽管人们已经认识到它对生长的重要性，但浮游植物对 Cu 缺乏的响应和适应的分子机制尚不清楚。在这项研究中，我们鉴定了主要的 Cu 调节蛋白，并在 Cu 限制和充足条件下测量了海洋鞭毛藻（CCMP 1005）的关键生理特征。由于光合效率（ΦPSII）下降，浮游植物在环境相关的 Cu 浓度（1 nM）下受到生长限制。在 Cu 限制的细胞中，与 Cu 充足的细胞相比，质体蓝蛋白的水平下降了 3 倍，最大光合电子传递速率降低。与光捕获复合物相关的蛋白质也响应 Cu 限制而下降，大概是为了适应减少的光合电子流，并避免光系统受到光损伤。与碳和氮同化相关的关键酶在低 Cu 细胞中被下调，C 和 N 摄取的稳态速率也是如此。相对较少的蛋白质被 Cu 限制上调，但其中包括两种参与脂肪酸氧化（FAO）的酶。FAO 的增加可能是由于氧化应激引起的细胞脂质周转率增加的迹象。一种含有三个重复蛋氨酸基序（MpgMgggM；MpgMggM）的假定转录因子在 Cu 限制细胞中显著增加。总的来说，这些结果提供了一个关于质体蓝蛋白依赖的硅藻如何调整代谢以应对慢性 Cu 缺乏的一般描述。
