Dissecting the Photoprotective Mechanism Encoded by the flv4-2 Operon: a Distinct Contribution of Sll0218 in Photosystem II Stabilization

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• 作者：Luca Bersanini ; Yagut Allahverdiyeva ; Natalia Battchikova ; Steffen Heinz ; Maija Lespinasse ; Essi Ruohisto ; Henna Mustila ; Jö ; rg Nickelsen ; Imre Vass and Eva-Mari Aro
• 刊名：Plant, Cell & Environment
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：40
• 期：3
• 页码：378-389
• 全文大小：949K
• ISSN：1365-3040

文摘

In Synechocystis sp. PCC 6803, the flv4-2 operon encodes the flavodiiron proteins Flv2 and Flv4 together with a small protein, Sll0218, providing photoprotection for Photosystem II (PSII). Here, the distinct roles of Flv2/Flv4 and Sll0218 were addressed, using a number of flv4-2 operon mutants. In the ∆sll0218 mutant, the presence of Flv2/Flv4 rescued PSII functionality as compared with ∆sll0218-flv2, where neither Sll0218 nor the Flv2/Flv4 heterodimer are expressed. Nevertheless, both the ∆sll0218 and ∆sll0218-flv2 mutants demonstrated deficiency in accumulation of PSII proteins suggesting a role for Sll0218 in PSII stabilization, which was further supported by photoinhibition experiments. Moreover, the accumulation of PSII assembly intermediates occurred in Sll0218-lacking mutants. The YFP-tagged Sll0218 protein localized in a few spots per cell at the external side of the thylakoid membrane, and biochemical membrane fractionation revealed clear enrichment of Sll0218 in the PratA-defined membranes, where the early biogenesis steps of PSII occur. Further, the characteristic antenna uncoupling feature of the ∆flv4-2 operon mutants is shown to be related to PSII destabilization in the absence of Sll0218. It is concluded that the Flv2/Flv4 heterodimer supports PSII functionality, while the Sll0218 protein assists PSII assembly and stabilization, including optimization of light harvesting.