Department of Chemistry, Chemical Biological Centre, Umeå University, S-90187, Umeå, Sweden.
The Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA.
Physiol Plant. 2019 May;166(1):165-180. doi: 10.1111/ppl.12932. Epub 2019 Feb 27.
High solar flux is known to diminish photosynthetic growth rates, reducing biomass productivity and lowering disease tolerance. Photosystem II (PSII) of plants is susceptible to photodamage (also known as photoinactivation) in strong light, resulting in severe loss of water oxidation capacity and destruction of the water-oxidizing complex (WOC). The repair of damaged PSIIs comes at a high energy cost and requires de novo biosynthesis of damaged PSII subunits, reassembly of the WOC inorganic cofactors and membrane remodeling. Employing membrane-inlet mass spectrometry and O -polarography under flashing light conditions, we demonstrate that newly synthesized PSII complexes are far more susceptible to photodamage than are mature PSII complexes. We examined these 'PSII birth defects' in barley seedlings and plastids (etiochloroplasts and chloroplasts) isolated at various times during de-etiolation as chloroplast development begins and matures in synchronization with thylakoid membrane biogenesis and grana membrane formation. We show that the degree of PSII photodamage decreases simultaneously with biogenesis of the PSII turnover efficiency measured by O -polarography, and with grana membrane stacking, as determined by electron microscopy. Our data from fluorescence, Q -inhibitor binding, and thermoluminescence studies indicate that the decline of the high-light susceptibility of PSII to photodamage is coincident with appearance of electron transfer capability Q → Q during de-etiolation. This rate depends in turn on the downstream clearing of electrons upon buildup of the complete linear electron transfer chain and the formation of stacked grana membranes capable of longer-range energy transfer.
高太阳通量会降低光合作用速率，减少生物量产量，并降低疾病耐受性。植物的光系统 II（PSII）在强光下容易受到光损伤（也称为光失活），导致严重的水氧化能力丧失和水氧化复合物（WOC）破坏。受损 PSII 的修复需要很高的能量成本，并且需要新合成受损 PSII 亚基、WOC 无机辅因子的重新组装以及膜重塑。我们在闪光条件下使用膜进样质谱和 O-极谱法证明，新合成的 PSII 复合物比成熟的 PSII 复合物更容易受到光损伤。我们在脱黄化过程中不同时间分离的大麦幼苗和质体（原质体和叶绿体）中检查了这些“PSII 出生缺陷”，因为叶绿体发育开始并与类囊体膜生物发生和基质膜形成同步成熟。我们表明，PSII 光损伤的程度与通过 O-极谱法测量的 PSII 周转率效率的生物发生同时降低，并且与电子显微镜确定的基质膜堆叠同时降低。我们从荧光、Q-抑制剂结合和热致发光研究的数据表明，PSII 对光损伤的高光照敏感性的下降与脱黄化过程中 Q→Q 电子转移能力的出现一致。该速率反过来又取决于在线性电子传递链完全建立后电子的下游清除，以及能够进行长程能量转移的堆叠基质膜的形成。
