Vajravel Sindhujaa, Laczkó-Dobos Hajnalka, Petrova Nia, Herman Éva, Kovács Terézia, Zakar Tomas, Todinova Svetla, Taneva Stefka, Kovács Lászlo, Gombos Zoltan, Tóth Tünde, Krumova Sashka
Institute of Plant Biology, Biological Research Centre, Szeged, Hungary.
Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland.
Photosynth Res. 2020 Aug;145(2):179-188. doi: 10.1007/s11120-020-00776-1. Epub 2020 Jul 27.
The major light-harvesting system in cyanobacteria, the phycobilisome, is an essential component of the photosynthetic apparatus that regulates the utilization of the natural light source-the Sun. Earlier works revealed that the thylakoid membrane composition and its physical properties might have an important role in antennas docking. Polyunsaturated lipids and xanthophylls are among the most significant modulators of the physical properties of thylakoid membranes. In the nature, the action of these molecules is orchestrated in response to environmental stimuli among which the growth temperature is the most influential. In order to further clarify the significance of thylakoid membrane physical properties for the phycobilisomes assembly (i.e. structural integrity) and their ability to efficiently direct the excitation energy towards the photosynthetic complexes, in this work, we utilize cyanobacterial Synechocystis sp. PCC 6803 mutants deficient in polyunsaturated lipids (AD mutant) and xanthophylls (RO mutant), as well as a strain depleted of both xanthophylls and polyunsaturated lipids (ROAD multiple mutant). For the first time, we discuss the effect of those mutations on the phycobilisomes assembly, integrity and functionality at optimal (30 °C) and moderate low (25 °C) and high (35 °C) temperatures. Our results show that xanthophyll depletion exerts a much stronger effect on both phycobilisome's integrity and the response of cells to growth at suboptimal temperatures than lipid unsaturation level. The strongest effects were observed for the combined ROAD mutant, which exhibited thermally destabilized phycobilisomes and a population of energetically uncoupled phycocyanin units.
蓝藻中的主要光捕获系统——藻胆体，是光合装置的重要组成部分，它调控着对自然光源——太阳的利用。早期研究表明，类囊体膜的组成及其物理性质可能在天线对接中发挥重要作用。多不饱和脂质和叶黄素是类囊体膜物理性质最重要的调节因子之一。在自然界中，这些分子的作用是根据环境刺激进行协调的，其中生长温度的影响最为显著。为了进一步阐明类囊体膜物理性质对藻胆体组装（即结构完整性）及其将激发能有效导向光合复合体能力的重要性，在本研究中，我们利用了缺乏多不饱和脂质的蓝藻集胞藻PCC 6803突变体（AD突变体）、缺乏叶黄素的突变体（RO突变体）以及同时缺乏叶黄素和多不饱和脂质的菌株（ROAD多重突变体）。我们首次讨论了这些突变在最佳温度（30°C）、适度低温（25°C）和高温（35°C）下对藻胆体组装、完整性和功能的影响。我们的结果表明，与脂质不饱和度水平相比，叶黄素的缺失对藻胆体的完整性以及细胞在次优温度下生长的反应具有更强的影响。对于组合的ROAD突变体观察到了最强的影响，该突变体表现出热不稳定的藻胆体和一群能量解偶联的藻蓝蛋白单元。
