As an alternative electron sink, chlororespiration, comprised of the NAD(P)H dehydrogenase complex and plastid terminal plastoquinone oxidase, may play a significant role for sustaining the redox equilibrium between stroma and thylakoid membrane. This study identified a distinct role of chlororespiration in the marine angiosperm Zostera marina, whose oxygen evolving complex (OEC) is prone to photo-inactivation as a result of its inherent susceptibility to excess irradiation. The strong connectivity between OEC peripheral proteins and key chlororespiratory enzymes, as demonstrated in the interaction network of differentially expressed genes, suggested that the recovery of photo-inactivated OEC was connected with chlororespiration. Chlorophyll fluorescence, transcriptome, and Western blot data verified a new physiological role of chlororespiration to function as photoprotection and generate proton gradient across the thylakoid membrane for the recovery of photo-inactivated OEC. Chlororespiration was only activated in darkness following excess irradiation exposure, which might be related to the electron deficiency in the electron transport chain because of the continuous impairment of OEC. The activation of chlororespiration in Z. marina was prone to proactivity, which was also supported by the further activation of the oxidative pentose-phosphate pathway synthesizing NADPH to meet the demand of chlororespiration during darkness. This phenomenon is distinct from the common assumption that chlororespiration is prone to consuming redundant reducing power during the short transition phase from light to dark.

中文翻译：

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在海洋被子植物Zostera marina，光致呼吸作用是对光灭活的放氧复合物的光保护作用。

作为替代的电子吸收体，由NAD（P）H脱氢酶复合物和质体末端质体醌氧化酶组成的氯呼吸作用可能对维持基质和类囊体膜之间的氧化还原平衡起重要作用。这项研究确定了氯呼吸作用在海洋被子植物Zostera marina中的独特作用，其氧释放复合物（OEC）由于其固有的易受过度辐射的影响而易于光灭活。如差异表达基因的相互作用网络所示，OEC外围蛋白与关键的氯呼吸酶之间的强连通性表明光灭活的OEC的恢复与氯呼吸有关。叶绿素荧光，转录组和蛋白质印迹数据验证了氯呼吸的新生理作用，可起到光保护作用并在类囊体膜上产生质子梯度，从而恢复光灭活的OEC。仅在过多的辐射暴露之后，才在黑暗中激活呼吸作用，这可能是由于OEC的持续损害而与电子传输链中的电子缺乏有关。滨海假单胞菌容易发生主动反应，这也得到了进一步活化合成NADPH的氧化戊糖-磷酸途径的支持，以满足黑暗中的氯呼吸需求。这种现象不同于通常的假设，即在从亮到暗的短暂过渡阶段中，氯呼吸容易消耗多余的还原能力。