Kovács L, Wiessner W, Kis M, Nagy F, Mende D, Demeter S
Biological Research Center, Hungarian Academy of Sciences, P.O.Box 521, H-6701, Szeged, Hungary.
Photosynth Res. 2000;65(3):231-47. doi: 10.1023/A:1010650532693.
The effect of acetate metabolism on the light energy distribution between the two photosystems, on the PS II/PS I stoichiometry and on the expression of psbA and psbB and psaA genes was investigated in the green alga, Chlamydobotrys stellata during autotrophic (CO(2)), mixotrophic (CO(2) plus acetate) and photoheterotrophic (only acetate) cultivation. It was observed that acetate assimilation in the glyoxylate cycle resulted in a large drop in the ATP content and a concomitant increase in the NADPH content of the cells. The combined effect of high NADPH concentration and linear electron transport brought about an over-reduction of the inter-photosystem electron transport components. The reduced state of the inter-photosystem components initiated a state 1/state 2 transition of LHC II and a decrease in the PS II/PS I ratio. The PS II/ PS I ratio was reduced because the synthesis of PS II reaction centers was repressed and that of the PS I reaction centers was slightly enhanced by acetate cultivation. The amount of PsbA and PsbB proteins of PS II and the abundance of psbA mRNA decreased. The abundance of PS I PsaA protein and psaAmRNA were only slightly increased. All of the acetate-induced effects were reversible when the cells were transferred back to an acetate-free medium. Our observations demonstrate that the expression of the PS II psbA and psbB and PS I psaA genes is regulated by the redox state of the inter-photosystem components at the transcriptional level. Experiments carried out in the presence of DBMIB which facilitates the reduction of plastoquinone pool indicate that the expression of genes encoding the components of PS II and PS I are controlled by the redox state of a component (cytochrome b/f complex) located behind the plastoquinone pool.
在绿藻星芒鼓藻进行自养（CO₂）、混养（CO₂加乙酸盐）和光异养（仅乙酸盐）培养期间，研究了乙酸盐代谢对两个光系统之间光能分配、PS II/PS I化学计量以及psbA、psbB和psaA基因表达的影响。观察到乙醛酸循环中乙酸盐的同化导致细胞中ATP含量大幅下降，同时NADPH含量增加。高NADPH浓度和线性电子传递的综合作用导致光系统间电子传递组分过度还原。光系统间组分的还原状态引发了LHC II的状态1/状态2转变以及PS II/PS I比值下降。PS II/PS I比值降低是因为乙酸盐培养抑制了PS II反应中心的合成，而PS I反应中心的合成略有增强。PS II的PsbA和PsbB蛋白量以及psbA mRNA丰度下降。PS I PsaA蛋白和psaA mRNA的丰度仅略有增加。当细胞转移回无乙酸盐培养基时，所有乙酸盐诱导的效应都是可逆的。我们的观察结果表明，PS II的psbA和psbB以及PS I的psaA基因的表达在转录水平上受光系统间组分的氧化还原状态调节。在促进质体醌库还原的DBMIB存在下进行的实验表明，编码PS II和PS I组分的基因表达受位于质体醌库之后的一个组分（细胞色素b/f复合体）的氧化还原状态控制。
