Photosystems must balance between light harvesting to fuel the photosynthetic process for CO2 fixation and mitigating the risk of photodamage due to absorption of light energy in excess. Eukaryotic photosynthetic organisms evolved an array of pigment-binding proteins called light harvesting complexes constituting the external antenna system in the photosystems, where both light harvesting and activation of photoprotective mechanisms occur. In this work, the balancing role of CP29 and CP26 photosystem II antenna subunits was investigated in Chlamydomonas reinhardtii using CRISPR-Cas9 technology to obtain single and double mutants depleted of monomeric antennas. Absence of CP26 and CP29 impaired both photosynthetic efficiency and photoprotection: Excitation energy transfer from external antenna to reaction centre was reduced, and state transitions were completely impaired. Moreover, differently from higher plants, photosystem II monomeric antenna proteins resulted to be essential for photoprotective thermal dissipation of excitation energy by nonphotochemical quenching.

中文翻译：

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Photosystem II天线配合物CP26和CP29对于莱茵衣藻的非光化学淬灭是必不可少的。

光系统必须在集光以促进光合作用固定CO2和减轻因吸收过多光能而造成光害的风险之间取得平衡。真核生物的光合生物进化出了一系列色素结合蛋白，称为光收集复合物，构成了光系统中的外部天线系统，在那里光收集和光保护机制都发生了。在这项工作中，使用CRISPR-Cas9技术在莱茵衣藻中研究了CP29和CP26光系统II天线亚基的平衡作用，以获取耗尽单体天线的单突变和双突变。CP26和CP29的缺失会损害光合作用效率和光保护作用：减少了从外部天线到反应中心的激发能传递，国家过渡完全受到了损害。而且，与高等植物不同，光系统II单体天线蛋白对于通过非光化学猝灭的激发能的光保护性热耗散至关重要。