Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo
Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo
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DOI：
10.1104/pp.106.082339
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发表时间：
2006-08-01
期刊：
影响因子：
7.4
通讯作者：
Huner, Norman P. A.
中科院分区：
文献类型：
--
作者：
Ivanov, Alexander G.;Krol, Marianna;Huner, Norman P. A.
在铁胁迫的蓝细菌中，isiA（CP 43 '）蛋白的诱导伴随着围绕光系统I（PSI）三聚体的18个CP 43'蛋白的环的形成，并且被认为增加了CP 43 '-PSI超复合物内PSI的吸收截面。与这些体外研究相反，我们的体内测量未能证明铁应激细胞的两种菌株（聚球藻属PCC 7942和聚胞藻属PCC 6803）的PSI吸收截面的任何增加。我们报告说，铁应激细胞表现出减少的能力状态转换和有限的暗还原质体醌池，这占PSII相关的685 nm叶绿素荧光铁缺乏下的增加。这是伴随着较低的丰度的NADP-脱氢酶复合物和PSI相关的亚基PsaL，以及减少量的磷脂酰甘油。非变性聚丙烯酰胺凝胶电泳分离的叶绿素-蛋白质复合物表明，PSI的单体形式是有利于在铁胁迫下的PSI的三聚体形式。因此，我们证明了CP 43 '的诱导不会增加体内全细胞的PSI功能吸收截面，而是诱导PSI三聚体的单体化并降低状态转换的能力。我们讨论的作用CP 43 '作为一种有效的能量猝灭剂，光保护PSII和PSI在不利的环境条件下，在蓝藻体内。
The induction of the isiA (CP43') protein in iron-stressed cyanobacteria is accompanied by the formation of a ring of 18 CP43' proteins around the photosystem I ( PSI) trimer and is thought to increase the absorption cross section of PSI within the CP43'-PSI supercomplex. In contrast to these in vitro studies, our in vivo measurements failed to demonstrate any increase of the PSI absorption cross section in two strains ( Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803) of iron-stressed cells. We report that iron- stressed cells exhibited a reduced capacity for state transitions and limited dark reduction of the plastoquinone pool, which accounts for the increase in PSII-related 685 nm chlorophyll fluorescence under iron deficiency. This was accompanied by lower abundance of the NADP-dehydrogenase complex and the PSI-associated subunit PsaL, as well as a reduced amount of phosphatidylglycerol. Nondenaturating polyacrylamide gel electrophoresis separation of the chlorophyll-protein complexes indicated that the monomeric form of PSI is favored over the trimeric form of PSI under iron stress. Thus, we demonstrate that the induction of CP43' does not increase the PSI functional absorption cross section of whole cells in vivo, but rather, induces monomerization of PSI trimers and reduces the capacity for state transitions. We discuss the role of CP43' as an effective energy quencher to photoprotect PSII and PSI under unfavorable environmental conditions in cyanobacteria in vivo.