The OPR Protein MTHI1 Controls the Expression of Two Different Subunits of ATP Synthase CFo in Chlamydomonas reinhardtii

Shin Ichiro Ozawa, Marina Cavaiuolo, Domitille Jarrige, Richard Kuras, Mark Rutgers, Stephan Eberhard, Dominique Drapier, Francis André Wollman, Yves Choquet

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In the green alga Chlamydomonas (Chlamydomonas reinhardtii), chloroplast gene expression is tightly regulated posttranscriptionally by gene-specific trans-acting protein factors. Here, we report the identification of the octotricopeptide repeat protein MTHI1, which is critical for the biogenesis of chloroplast ATP synthase oligomycin-sensitive chloroplast coupling factor. Unlike most trans-acting factors characterized so far in Chlamydomonas, which control the expression of a single gene, MTHI1 targets two distinct transcripts: it is required for the accumulation and translation of atpH mRNA, encoding a subunit of the selective proton channel, but it also enhances the translation of atpI mRNA, which encodes the other subunit of the channel. MTHI1 targets the 5' untranslated regions of both the atpH and atpI genes. Coimmunoprecipitation and small RNA sequencing revealed that MTHI1 binds specifically a sequence highly conserved among Chlorophyceae and the Ulvale clade of Ulvophyceae at the 5' end of triphosphorylated atpH mRNA. A very similar sequence, located ∼60 nucleotides upstream of the atpI initiation codon, was also found in some Chlorophyceae and Ulvale algae species and is essential for atpI mRNA translation in Chlamydomonas. Such a dual-targeted trans-acting factor provides a means to coregulate the expression of the two proton hemi-channels.

Original languageEnglish
Pages (from-to)1179-1203
Number of pages25
JournalThe Plant cell
Issue number4
Publication statusPublished - Apr 1 2020


ASJC Scopus subject areas

  • Plant Science
  • Cell Biology

Cite this

Ozawa, S. I., Cavaiuolo, M., Jarrige, D., Kuras, R., Rutgers, M., Eberhard, S., Drapier, D., Wollman, F. A., & Choquet, Y. (2020). The OPR Protein MTHI1 Controls the Expression of Two Different Subunits of ATP Synthase CFo in Chlamydomonas reinhardtii. The Plant cell, 32(4), 1179-1203.