Greene B A, Allred D R, Morishige D T, Staehelin L A
Department of Molecular, Cellular and Developmental Biology, Box 347, University of Colorado, Boulder, Colorado 80309.
Plant Physiol. 1988 Jun;87(2):357-64. doi: 10.1104/pp.87.2.357.
The light-sensitive chlorophyll b (Chl b)-deficient oil yellow-yellow green (OY-YG) mutant of maize (Zea mays) grown under conditions of high light exhibits differential reductions in the accumulation of the three major Chl b-containing antenna complexes and characteristic changes in thylakoid architecture. When observed by freeze-fracture electron microscopy, the most notable changes in the OY-YG thylakoid structure are: (a) a major reduction in the number of 8 nanometer particles of the protoplasmic fracture face of stacked membrane regions (PFs) paralleled by a 60% reduction in the chlorophyll-proteins (CP) associated with the peripheral light harvesting complex (LHCII) for photosystem II (PSII) and which give rise to the LHCII oligomer/monomer (CPII()/CPII) bands on mildly dissociated green gels; (b) a sizable decrease in the proportion of 11 to 13 nanometer particles of the protoplasmic fracture face of unstacked membrane regions (PFu) that parallels the loss of light harvesting complex I (LHCI) antennae from photosystem I (PSI) centers and a 40% reduction of the band containing CP1 and LHCI (CPI()) on mildly dissociating green gels; (c) an unchanged or slightly increased average size of particles of the exoplasmic fracture face of stacked (or appressed) membrane regions (EFs) along with a relative increase in CP29, the postulated bound LHC of PSII, and of CP47 and CP43, PSII core antenna complexes. This latter result sets the OY-YG mutant apart from all other Chl b-deficient mutants studied to date, all of which possess EFs particles that are substantially reduced in size. Based on these findings, we postulate that the bound LHCII associated with EFs particles consists mostly of CP29 chlorophyll proteins and very little, if any, CPII()/CPII chlorophyll proteins. Indeed, the CPII()/CPII chlorophyll proteins may be exclusively associated with the ;peripheral' LHCII units that give rise to 8 nanometer PF particles. The differential effect of the Chl b deficiency on the accumulation of the three main antenna complexes (CPII()/CPII>CPI()>CP29) suggests, furthermore, that there is a hierarchy among Chl b-binding proteins, and that this hierarchy might be an integral part of long-term photoregulation mediating Chl b partitioning in the chloroplast.
在高光条件下生长的玉米（Zea mays）的光敏叶绿素b（Chl b）缺乏型油黄-黄绿色（OY-YG）突变体，其三种主要含Chl b的天线复合体的积累出现不同程度的减少，类囊体结构也发生了特征性变化。通过冷冻蚀刻电子显微镜观察，OY-YG类囊体结构最显著的变化是：（a）堆叠膜区域（PFs）原生质断裂面8纳米颗粒的数量大幅减少，与之平行的是，与光系统II（PSII）外周光捕获复合体（LHCII）相关的叶绿素蛋白（CP）减少了60%，这些叶绿素蛋白在轻度解离的绿色凝胶上产生LHCII寡聚体/单体（CPII()/CPII）条带；（b）非堆叠膜区域（PFu）原生质断裂面11至13纳米颗粒的比例大幅下降，这与光系统I（PSI）中心光捕获复合体I（LHCI）天线的丧失平行，并且在轻度解离的绿色凝胶上，含有CP1和LHCI（CPI()）的条带减少了40%；（c）堆叠（或紧密排列）膜区域（EFs）外质断裂面颗粒的平均大小不变或略有增加，同时PSII假定的结合LHC CP29以及PSII核心天线复合体CP47和CP43相对增加。后一个结果使OY-YG突变体与迄今为止研究的所有其他Chl b缺乏型突变体区分开来，所有其他突变体的EFs颗粒大小都大幅减小。基于这些发现，我们推测与EFs颗粒相关的结合LHCII主要由CP29叶绿素蛋白组成，如果有CPII()/CPII叶绿素蛋白的话也非常少。事实上，CPII()/CPII叶绿素蛋白可能仅与产生8纳米PF颗粒的“外周”LHCII单元相关。此外，Chl b缺乏对三种主要天线复合体积累的不同影响（CPII()/CPII>CPI()>CP29）表明，Chl b结合蛋白之间存在层次结构，并且这种层次结构可能是叶绿体中Chl b分配长期光调节的一个组成部分。
