Küpper Hendrik, Šetlík Ivan, Šetliková Eva, Ferimazova Naila, Spiller Martin, Küpper Frithjof C
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, Postfach M665, D-78457 Konstanz, Germany. Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, CZ-37981 Třeboň, Czech Republic. Current address: Cornell University, US Plant, Soil and Nutrition Laboratory USDA-ARS, Ithaca, New York 14853, USA. Corresponding author; email:
Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, CZ-37981 Třeboň, Czech Republic. Institute of Physical Biology, University of South Bohemia, 373 33 Nové Hrady, Czech Republic.
Funct Plant Biol. 2003 Jan;30(12):1187-1196. doi: 10.1071/FP03129.
The in vivo substitution of Mg in chlorophyll by heavy metals is an important damage mechanism in heavy metal-stressed plants that leads to an inhibition of photosynthesis. In photosynthetic organisms with LHC II antennae, the in vivo substitution of Mg by Cu occurs particularly readily under low irradiance with a dark phase - a phenomenon referred to as 'shade reaction'. In the present study the limiting steps of the shade reaction were investigated with synchronised cultures of the chlorococcal green alga Scenedesmus quadricauda (Turp.) Bréb. The rate of copper chlorophyll formation during shade reaction was shown to be controlled by several factors; firstly, in some phases of the cell cycle, especially at the end of the light period, Mg in chlorophyll was not accessible to substitution. This pattern is likely to be caused by cell cycle-dependent changes in photosynthesis and thylakoid ultrastructure, which were published earlier and are reconsidered in the discussion of the present work. Secondly, prolonged culture in a medium containing 3 μM Cu reversibly increased the resistance of the strain to Cu. Culturing without added Cu lowered the threshold concentrations of various deleterious effects more than 10-fold within 8 months of de-adaptation. Adaptation to high Cu levels is discussed in the context of studies of the regulation of metal transporter proteins. In addition, it was also observed that toxic Cu levels impaired photosynthesis sooner than cell division.
叶绿素中镁在体内被重金属取代是重金属胁迫植物中的一种重要损伤机制，会导致光合作用受到抑制。在具有LHC II天线的光合生物中，在低光照且有暗期的条件下，镁特别容易在体内被铜取代——这种现象被称为“阴蔽反应”。在本研究中，利用绿球藻纲绿藻四尾栅藻（Scenedesmus quadricauda (Turp.) Bréb.）的同步培养物研究了阴蔽反应的限制步骤。结果表明，阴蔽反应过程中铜叶绿素的形成速率受多种因素控制；首先，在细胞周期的某些阶段，尤其是在光照期结束时，叶绿素中的镁无法被取代。这种模式可能是由光合作用和类囊体超微结构中依赖细胞周期的变化引起的，这些变化已在之前发表，并在本工作的讨论中重新进行了考量。其次，在含有3 μM铜的培养基中长时间培养会使该菌株对铜的抗性可逆地增加。在去适应的8个月内，不添加铜进行培养会使各种有害效应的阈值浓度降低10倍以上。在金属转运蛋白调控研究的背景下讨论了对高铜水平的适应。此外，还观察到有毒的铜水平比细胞分裂更早地损害光合作用。
