Distinct functions for the two PsbP-like proteins PPL1 and PPL2 in the chloroplast thylakoid lumen of arabidopsis
Distinct functions for the two PsbP-like proteins PPL1 and PPL2 in the chloroplast thylakoid lumen of arabidopsis
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DOI：
10.1104/pp.107.105866
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发表时间：
2007-11-01
期刊：
影响因子：
7.4
通讯作者：
Sato, Fumihiko
中科院分区：
文献类型：
--
作者：
Ishihara, Seiko;Takabayashi, Atsushi;Sato, Fumihiko
PSBP是光系统II(PSII)的一个外在亚基，是一种核编码蛋白，可在体内优化水的分解反应。除了PSBP外，高等植物还有两个PSBP同源物的核编码基因(PSBP-like Proteins[ppls])，它们与蓝藻PSBP同源物(Blueop)具有显著的序列相似性；然而，ppls在高等植物中的功能尚未阐明。在这项研究中，我们鉴定了两个PPL1和PPL2中的任何一个缺失的拟南芥突变体。系统发育分析表明，PPL1可能是Blueop的直系同源基因，PPL2和PSBP可能与PPL1有相似关系。基因表达谱分析表明，PPL1在胁迫条件下表达，PPL2与叶绿体NAD(P)H脱氢酶(NDH)复合体的亚单位共表达。与此一致的是，ppl1突变体的PSII活性对强光的敏感性高于野生型，并且ppl1植株光抑制的PSII活性的恢复延迟。因此，光损伤PSII的有效修复需要PPL1。此外，在ppl2突变体中，类囊体叶绿体NDH复合体的化学计量水平和活性严重下降，表明Ppl2是一种新的类囊体腔因子，需要积累叶绿体NDH复合体。这些结果表明，在内生共生和随后的基因转移到宿主核的过程中，古代蓝藻的Bluop进化成PPL1、PPL2和PSBP，它们在拟南芥的光合作用电子传递中都有不同的作用。
PsbP, an extrinsic subunit of photosystem II ( PSII), is a nuclear- encoded protein that optimizes the water- splitting reaction in vivo. In addition to PsbP, higher plants have two nuclear- encoded genes for PsbP homologs ( PsbP- like proteins [ PPLs]) that show significant sequence similarity to a cyanobacterial PsbP homolog ( cyanoP); however, the function of PPLs in higher plants has not yet been elucidated. In this study, we characterized Arabidopsis ( Arabidopsis thaliana) mutants lacking either of two PPLs, PPL1 and PPL2. Phylogenetic analysis suggests that PPL1 would be an ortholog of cyanoP, and PPL2 and PsbP may have a paralogous relationship with PPL1. Analysis on mRNA expression profiles showed that PPL1 expressed under stress conditions and PPL2 coexpressed with the subunits of chloroplast NAD( P) H dehydrogenase ( NDH) complex. Consistent with these suggestions, PSII activity in a ppl1 mutant was more sensitive to high- intensity light than wild type, and the recovery of photoinhibited PSII activity was delayed in ppl1 plants. Therefore, PPL1 is required for efficient repair of photodamaged PSII. Furthermore, the stoichiometric level and activity of the chloroplast NDH complex in thylakoids were severely decreased in a ppl2 mutant, demonstrating that PPL2 is a novel thylakoid lumenal factor required for accumulation of the chloroplast NDH complex. These results suggest that during endosymbiosis and subsequent gene transfer to the host nucleus, cyanoP from ancient cyanobacteria evolved into PPL1, PPL2, and PsbP, and each of them has a distinct role in photosynthetic electron transfer in Arabidopsis.