Two Chlamydomonas OPR proteins stabilize chloroplast mRNAs encoding small subunits of photosystem II and cytochrome b6 f.
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 b6 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 b6 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.
['Wang|Fei|F|', 'Johnson|Xenie|X|', 'Cavaiuolo|Marina|M|', 'Bohne|Alexandra-Viola|AV|', 'Nickelsen|Joerg|J|', 'Vallon|Olivier|O|']
D016825:Chlamydomonas reinhardtii D045346:Cytochrome b6f Complex D018506:Gene Expression Regulation, Plant D009154:Mutation D045332:Photosystem II Protein Complex D010940:Plant Proteins D020871:RNA Stability D018747:RNA, Chloroplast
photosystem II chloroplast gene expression Chlamydomonas reinhardtii OctotricoPeptide Repeat petG psbI RNA footprint RNA-binding protein cytochrome b6f