Two Chlamydomonas OPR proteins stabilize chloroplast mRNAs encoding small subunits of photosystem II and cytochrome b6f. (June 2015)

• Record Type: Journal Article
• Authors: Wang, Fei; Johnson, Xenie; Cavaiuolo, Marina; Bohne, Alexandra‐Viola; Nickelsen, Joerg; Vallon, Olivier
• Is Part Of: Plant journal. Volume 82:Number 5(2015:Jun.)
• Page Start: 861
• Page End: 873
• Publication Date: 2015-06
• Subjects: OctotricoPeptide Repeat -- chloroplast gene expression -- photosystem II -- cytochrome b6f -- Chlamydomonas reinhardtii -- psbI -- petG -- RNA‐binding protein -- RNA footprint; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12858
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: In plants and algae, chloroplast gene expression is controlled by nucleus‐encoded proteins that bind to mRNAs in a specific manner, stabilizing mRNAs or promoting their splicing, editing, or translation. Here, we present the characterization of two mRNA stabilization factors of the green alga Chlamydomonas reinhardtii, which both belong to the OctotricoPeptide Repeat (OPR) family. MCG1 is necessary to stabilize the petG mRNA, encoding a small subunit of the cytochrome b 6 f complex, while MBI1 stabilizes the psbI mRNA, coding for a small subunit of photosystem II. In the mcg1 mutant, the small RNA footprint corresponding to the 5′‐end of the petG transcript is reduced in abundance. In both cases, the absence of the small subunit perturbs assembly of the cognate complex. Whereas PetG is essential for formation of a functional cytochrome b 6 f dimer, PsbI appears partly dispensable as a low level of PSII activity can still be measured in its absence. Thus, nuclear control of chloroplast gene expression is not only exerted on the major core subunits of the complexes, but also on small subunits with a single transmembrane helix. While OPR proteins have thus far been involved in translation or trans‐splicing of plastid mRNAs, our results expand the potential roles of this repeat family to their stabilization. Significance Statement: MCG1 and MBI1 stabilize mRNAs for small subunits of cytochrome b6f and PSII. This is the first time that OPR proteins are shown to act as mRNA stabilization factors.