Low light‐regulated intramolecular disulfide fine‐tunes the role of PTOX in Arabidopsis. (2nd December 2021)

• Record Type: Journal Article
• Authors: Rog, Ido; Chaturvedi, Amit Kumar; Tiwari, Vivekanand; Danon, Avihai
• Is Part Of: Plant journal. Volume 109:Number 3(2022)
• Page Start: 585
• Page End: 597
• Publication Date: 2021-12-02
• Subjects: regulatory disulfide -- low‐light regulation -- photosynthesis‐derived redox signals -- chloroplast -- Arabidopsis thaliana; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.15579
• Languages: English
• ISSNs: 0960-7412

Abstract

SUMMARY: Disulfide‐based regulation links the activity of numerous chloroplast proteins with photosynthesis‐derived redox signals. The plastid terminal oxidase (PTOX) is a thylakoid‐bound plastoquinol oxidase that has been implicated in multiple roles in the light and in the dark, which could require different levels of PTOX activity. Here we show that Arabidopsis PTOX contains a conserved C‐terminus domain (CTD) with cysteines that evolved progressively following the colonization of the land by plants. Furthermore, the CTD contains a regulatory disulfide that is in the oxidized state in the dark and is rapidly reduced, within 5 min, in low light intensity (1–5 µE m −2 sec −1 ). The reduced PTOX form in the light was reoxidized within 15 min after transition to the dark. Mutation of the cysteines in the CTD prevented the formation of the oxidized form. This resulted in higher levels of reduced plastoquinone when measured at transition to the onset of low light. This is consistent with the reduced state of PTOX exhibiting diminished PTOX oxidase activity under conditions of limiting PQH2 substrate. Our findings suggest that AtPTOX‐CTD evolved to provide light‐dependent regulation of PTOX activity for the adaptation of plants to terrestrial conditions. Significance Statement: Arabidopsis plastid terminal oxidase (PTOX) contains a conserved C‐terminus domain (CTD), with cysteines that evolved progressively following the colonization of the land by plants. The CTD contains a regulatory disulfide that is in the oxidized state in the dark and is rapidly reduced under low light intensity. Our findings suggest that AtPTOX‐CTD evolved to provide light‐dependent regulation of PTOX activity for the adaptation of plants to terrestrial conditions.