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Mol Plant. 2017 Jan 9;10(1):143-154. doi: 10.1016/j.molp.2016.10.009. Epub 2016 Oct 21.

Dynamic Changes of IsiA-Containing Complexes during Long-Term Iron Deficiency in Synechocystis sp. PCC 6803.

Author information

1
Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China; College of Life Sciences, University of the Chinese Academy of Sciences, Beijing 100039, China.
2
Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
3
Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China. Electronic address: wangqiang@ihb.ac.cn.

Abstract

Iron stress-induced protein A (IsiA), a major chlorophyll-binding protein in the thylakoid membrane, is significantly induced under iron deficiency conditions. Using immunoblot analysis and 77 K fluorescence spectroscopy combined with sucrose gradient fractionation, we monitored dynamic changes of IsiA-containing complexes in Synechocystis sp. PCC 6803 during exposure to long-term iron deficiency. Within 3 days of exposure to iron deficiency conditions, the initially induced free IsiA proteins preferentially conjugated to PS I trimer to form IsiA18-PS I trimers, which serve as light energy collectors for efficiently transmitting energy to PS I. With prolonged iron deficiency, IsiA proteins assembled either into IsiA aggregates or into two other types of IsiA-PS I supercomplexes, namely IsiA-PS I high fluorescence supercomplex (IHFS) and IsiA-PS I low fluorescence supercomplex (ILFS). Further analysis revealed a role for IsiA as an energy dissipater in the IHFS and as an energy collector in the ILFS. The trimeric structure of PS I mediated by PsaL was found to be indispensable for the formation of IHFS/ILFS. Dynamic changes in IsiA-containing complexes in cyanobacteria during long-term iron deficiency may represent an adaptation to iron limitation stress for flexible light energy distribution, which balances electron transfer between PS I and PS II, thus minimizing photooxidative damage.

KEYWORDS:

IsiA-PS I high fluorescence supercomplex; IsiA-PS I low fluorescence supercomplex; IsiA-containing complexes; Synechocystis sp. PCC 6803; iron deficiency

PMID:
27777125
DOI:
10.1016/j.molp.2016.10.009
[Indexed for MEDLINE]
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