Havaux Michel, Rumeau Dominique, Ducruet Jean-Marc
CEA/Cadarache, DSV, DEVM, Laboratoire d'Ecophysiologie de la Photosynthèse, UMR 6191 CNRS-CEA-Aix Marseille II, F-13108 Saint-Paul-lez-Durance, France.
Biochim Biophys Acta. 2005 Sep 30;1709(3):203-13. doi: 10.1016/j.bbabio.2005.07.010.
Far-red illumination of plant leaves for a few seconds induces a delayed luminescence rise, or afterglow, that can be measured with the thermoluminescence technique as a sharp band peaking at around 40-45 degrees C. The afterglow band is attributable to a heat-induced electron flow from the stroma to the plastoquinone pool and the PSII centers. Using various Arabidopsis and tobacco mutants, we show here that the electron fluxes reflected by the afterglow luminescence follow the pathways of cyclic electron transport around PSI. In tobacco, the afterglow signal relied mainly on the ferredoxin-quinone oxidoreductase (FQR) activity while the predominant pathway responsible for the afterglow in Arabidopsis involved the NAD(P)H dehydrogenase (NDH) complex. The peak temperature T(m) of the afterglow band varied markedly with the light conditions prevailing before the TL measurements, from around 30 degrees C to 45 degrees C in Arabidopsis. These photoinduced changes in Tm followed the same kinetics and responded to the same light stimuli as the state 1-state 2 transitions. PSII-exciting light (leading to state 2) induced a downward shift while preillumination with far-red light (inducing state 1) caused an upward shift. However, the light-induced downshift was strongly inhibited in NDH-deficient Arabidopsis mutants and the upward shift was cancelled in plants durably acclimated to high light, which can perform normal state transitions. Taken together, our results suggest that the peak temperature of the afterglow band is indicative of regulatory processes affecting electron donation to the PQ pool which could involve phosphorylation of NDH. The afterglow thermoluminescence band provides a new and simple tool to investigate the cyclic electron transfer pathways and to study their regulation in vivo.
用远红光照射植物叶片几秒钟会诱导延迟发光增强，即余辉，可通过热发光技术测量，表现为在40 - 45摄氏度左右出现尖锐峰的谱带。余辉谱带归因于热诱导的电子从基质流向质体醌库和光系统II中心。利用各种拟南芥和烟草突变体，我们在此表明，余辉发光反映的电子通量遵循围绕光系统I的循环电子传递途径。在烟草中，余辉信号主要依赖铁氧化还原蛋白 - 醌氧化还原酶（FQR）活性，而拟南芥中负责余辉的主要途径涉及NAD(P)H脱氢酶（NDH）复合体。在拟南芥中，余辉谱带的峰值温度T(m)随热发光测量前的光照条件显著变化，范围从约30摄氏度到45摄氏度。这些光诱导的Tm变化遵循与状态1 - 状态2转变相同的动力学，并对相同的光刺激做出反应。光系统II激发光（导致状态2）诱导向下移动，而用远红光预照射（诱导状态1）导致向上移动。然而，在缺乏NDH的拟南芥突变体中，光诱导的向下移动受到强烈抑制，而在长期适应高光的植物中向上移动被消除，这些植物能够进行正常的状态转变。综上所述，我们的结果表明，余辉谱带的峰值温度指示了影响向质体醌库供电子的调节过程，这可能涉及NDH的磷酸化。余辉热发光谱带为研究循环电子传递途径及其体内调节提供了一种新的简单工具。
