The chloroplast ycf7 (petL) open reading frame of Chlamydomonas reinhardtii encodes a small functionally important subunit of the cytochrome b6f complex

Yuichiro Takahashi, Michèle Rahire, Cécile Breyton, Jean Luc Popot, Pierre Joliot, Jean David Rochaix

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

The small chloroplast open reading frame ORF43 (ycf7) of the green unicellular alga Chlamydomonas reinhardtii is cotranscribed with the psaC gene and ORF58. While ORF58 has been found only in the chloroplast genome of C. reinhardtii, ycf7 has been conserved in land plants and its sequence suggests that its product is a hydrophobic protein with a single transmembrane α helix. We have disrupted ORF58 and ycf 7 with the aadA expression cassette by particle-gun mediated chloroplast transformation. While the ORF58::aadA transformants are indistinguishable from wild type, photoautotrophic growth of the ycf 7::aadA transformants is considerably impaired. In these mutant cells, the amount of cytochrome b6f complex is reduced to 25-50% of wild-type level in mid-exponential phase, and the rate of transmembrane electron transfer per b6f complex measured in vivo under saturating light is three to four times slower than in wild type. Under subsaturating light conditions, the rate of the electron transfer reactions within the b6f complex is reduced more strongly in the mutant than in the wild type by the proton electrochemical gradient. The ycf 7 product (Ycf 7) is absent in mutants deficient in cytochrome b6f complex and present in highly purified b6f complex from the wild-type strain. Ycf7-less complexes appear more fragile than wild-type complexes and selectively lose the Rieske iron-sulfur protein during purification. These observations indicate that Ycf7 is an authentic subunit of the cytochrome b6f complex, which is required for its stability, accumulation and optimal efficiency, We therefore propose to rename the ycf 7 gene petL.

Original languageEnglish
Pages (from-to)3498-3506
Number of pages9
JournalEMBO Journal
Volume15
Issue number14
DOIs
Publication statusPublished - Jul 15 1996

Keywords

  • Chlamydomonas reinhardtii
  • Chloroplast open reading frame
  • Chloroplast transformation
  • Cytochrome bf complex

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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