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

• Published in: The Plant cell Vol. 32; no. 4; pp. 1179 - 1203
• Main Authors: Ozawa, Shin-Ichiro, Cavaiuolo, Marina, Jarrige, Domitille, Kuras, Richard, Rutgers, Mark, Eberhard, Stephan, Drapier, Dominique, Wollman, Francis-André, Choquet, Yves
• Format: Journal Article
• Language: English
• Published: England American Society of Plant Biologists (ASPB) 01.04.2020; American Society of Plant Biologists
• Subjects: 5' Untranslated Regions - genetics; Amino Acid Sequence; Base Sequence; Biochemistry, Molecular Biology; Chlamydomonas reinhardtii - enzymology; Chlamydomonas reinhardtii - genetics; Chloroplast Proton-Translocating ATPases - genetics; Chloroplast Proton-Translocating ATPases - metabolism; Gene Expression Regulation, Plant; Genes, Reporter; Genetic Complementation Test; Life Sciences; Molecular biology; Mutation - genetics; Phenotype; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Protein Binding; Protein Biosynthesis; Protein Subunits - genetics; Protein Subunits - metabolism; RNA Stability - genetics; RNA, Messenger - genetics; RNA, Messenger - metabolism
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.19.00770

In the green alga Chlamydomonas ( ), chloroplast gene expression is tightly regulated posttranscriptionally by gene-specific -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 -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 mRNA, encoding a subunit of the selective proton channel, but it also enhances the translation of mRNA, which encodes the other subunit of the channel. MTHI1 targets the 5' untranslated regions of both the and 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 mRNA. A very similar sequence, located ∼60 nucleotides upstream of the initiation codon, was also found in some Chlorophyceae and Ulvale algae species and is essential for mRNA translation in Chlamydomonas. Such a dual-targeted -acting factor provides a means to coregulate the expression of the two proton hemi-channels.