Sarvikas Päivi, Hakala Marja, Pätsikkä Eija, Tyystjärvi Taina, Tyystjärvi Esa
Plant Physiology and Molecular Biology, Department of Biology, University of Turku, Finland.
Plant Cell Physiol. 2006 Mar;47(3):391-400. doi: 10.1093/pcp/pcj006. Epub 2006 Jan 13.
Photoinhibition is light-induced inactivation of PSII. Hypotheses about the photoreceptor(s) of photoinhibition include the Chl antenna of PSII, manganese of the oxygen-evolving complex (OEC), uncoupled Chl and iron-sulfur centres. We measured the action spectrum of photoinhibition in vivo from wild-type Arabidopsis thaliana L. and from the npq1-2 and npq4-1 mutants defective in non-photochemical quenching (NPQ) of excitations of the PSII antenna. The in vivo action spectrum was found to resemble closely the in vitro action spectra published for photoinhibition. We compared the action spectrum with absorbance spectra of model compounds of the OEC complex and other potential photoreceptors of photoinhibition. The comparison suggests that both manganese and Chl function as photoreceptors in photoinhibition. In accordance with the function of two types of photoreceptors in photoinhibition, NPQ was found to offer only partial protection against photoinhibition at visible wavelengths. The low protective efficiency of NPQ supports the conclusion that the Chl antenna of PSII is not the only photoreceptor of photoinhibition. Comparison of the action spectrum of photoinhibition with the emission spectrum of sunlight shows that the UV part of sunlight is responsible for the major part of photoinhibition under natural conditions.
光抑制是指光诱导的PSII失活。关于光抑制的光感受器的假说包括PSII的叶绿素天线、放氧复合体（OEC）的锰、未偶联的叶绿素和铁硫中心。我们测量了野生型拟南芥以及PSII天线激发的非光化学猝灭（NPQ）存在缺陷的npq1-2和npq4-1突变体体内光抑制的作用光谱。发现体内作用光谱与已发表的光抑制体外作用光谱非常相似。我们将该作用光谱与OEC复合体的模型化合物以及光抑制的其他潜在光感受器的吸收光谱进行了比较。比较结果表明，锰和叶绿素在光抑制中均作为光感受器发挥作用。根据光抑制中两种类型光感受器的功能，发现NPQ在可见光波长下仅对光抑制提供部分保护。NPQ的低保护效率支持了PSII的叶绿素天线不是光抑制的唯一光感受器这一结论。光抑制作用光谱与太阳光发射光谱的比较表明，在自然条件下，太阳光的紫外线部分是光抑制的主要原因。
