Peterson Richard B
Department of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, New Haven, 06511, USA.
Photosynth Res. 2005 Aug;85(2):205-19. doi: 10.1007/s11120-005-3106-7.
Application of multiple probes to systems that carry specific mutations provides a powerful means for studying how known regulators of light utilization interact in vivo. Two lines of Arabidopsis thaliana were studied, each carrying a unique lesion in the nuclear psbS gene encoding a 22-kDa pigment-binding protein (PS II-S) essential for full expression of photoprotective, rapid-phase, nonphotochemical quenching of chlorophyll fluorescence (NPQ). The PS II-S protein is absent in line npq4-1 due to deletion of psbS. Line npq4-9 expresses normal levels of PS II-S but carries a single amino acid substitution that lowers NPQ capacity by about 50%. A prior report [Peterson RB and Havir EA (2001) Planta 214: 142-152] described an altered pattern of redox states of the acceptor side of Photosystem II (PS II) and donor side of Photosystem I (PS I) for npq4-9 suggesting that interphotosystem electron transport may be restricted by a higher transthylakoid DeltapH in this line. In vivo steady state fluorescence and absorbance measurements (820 nm) confirmed these earlier observations for line npq4-9 but not for npq4-1. Thus, the prior results cannot be correlated simply to a loss of NPQ capacity. Likewise, the kinetics of the 820-nm absorbance change did not indicate a substantial effect of psbS genotype on electron flow from plastoquinol to PS I. A simple model is proposed to relate linear electron transport rate (measured gasometrically) to a parameter (based on fluorescence) that provides a relative measure of the density of excitation available for photochemistry in PS II. Surprisingly, analyses using this model suggested that the in vivo midpoint potential of the primary quinone acceptor in PS II (Q(A)) is lowered in both psbS mutant lines. This heretofore-unsuspected role for PS II-S is discussed with regard to: (1) numerous prior reports indicating plasticity of the redox potential of Q(A) and (2) the basis for the contrasting regulation of quantum yields of PS I and II in npq4-1 and npq4-9.
将多个探针应用于携带特定突变的系统，为研究已知的光利用调节因子在体内如何相互作用提供了一种强大的手段。研究了两株拟南芥，每株在编码22 kDa色素结合蛋白（PS II-S）的核psbS基因中都有一个独特的损伤，该蛋白对于叶绿素荧光的光保护、快速相非光化学猝灭（NPQ）的充分表达至关重要。在npq4-1品系中，由于psbS缺失，PS II-S蛋白不存在。npq4-9品系表达正常水平的PS II-S，但有一个单氨基酸取代，使NPQ能力降低约50%。先前的一份报告[Peterson RB和Havir EA（2001年）《植物》214：142 - 152]描述了npq4-9品系中光系统II（PS II）受体侧和光系统I（PS I）供体侧氧化还原状态的改变模式，表明该品系中跨类囊体ΔpH升高可能会限制光合系统间的电子传递。体内稳态荧光和吸光度测量（820 nm）证实了npq4-9品系的这些早期观察结果，但npq4-1品系并非如此。因此，先前的结果不能简单地与NPQ能力的丧失相关联。同样，820 nm吸光度变化的动力学也未表明psbS基因型对从质体醌到PS I的电子流有实质性影响。提出了一个简单模型，将线性电子传递速率（通过气体测量法测量）与一个参数（基于荧光）相关联，该参数提供了PS II中可用于光化学的激发密度的相对测量值。令人惊讶的是，使用该模型的分析表明，在两个psbS突变品系中，PS II中初级醌受体（Q(A)）的体内中点电位都降低了。本文就以下方面讨论了PS II-S这一此前未被怀疑的作用：（1）众多先前报告表明Q(A)氧化还原电位具有可塑性；（2）npq4-1和npq4-9品系中PS I和II量子产率对比调节的基础。
