Disruption of the plastid $ycf10$ open reading frame affects uptake of inorganic carbon in the chloroplast of Chlamydomonas - CEA - Commissariat à l’énergie atomique et aux énergies alternatives Accéder directement au contenu
Article Dans Une Revue EMBO Journal Année : 1997

Disruption of the plastid $ycf10$ open reading frame affects uptake of inorganic carbon in the chloroplast of Chlamydomonas

Résumé

The product of the chloroplast $ycf10$ gene has been localized in the inner chloroplast envelope membrane (Sasaki et al., 1993) and found to display sequence homology with the cyanobacterial CotA product which is altered in mutants defective in CO$_2$ transport and proton extrusion (Katoh et al., 1996a,b). In Chlamydomonas reinhardtii, $ycf10$, located between the $psbI$ and $atpH$ genes, encodes a putative hydrophobic protein of 500 residues, which is considerably larger than its higher plant homologue because of a long insertion that separates the conserved N and C termini. Using biolistic transformation, we have disrupted ycf10 with the chloroplast aadA expression cassette and examined the phenotype of the homoplasmic transformants. These were found to grow both photoheterotrophically and photoautotrophically under low light, thereby revealing that the Ycf10 product is not essential for the photosynthetic reactions. However, under high light these transformants did not grow photoautotrophically and barely photoheterotrophically. The increased light sensitivity of the transformants appears to result from a limitation in photochemical energy utilization and/or dissipation which correlates with a greatly diminished photosynthetic response to exogenous (CO$_2$ + HCO$_3^-$), especially under conditions where the chloroplast inorganic carbon transport system is not induced. Mass spectrometric measurements with either whole cells or isolated chloroplasts from the transformants revealed that the CO$_2$ and HCO$_3^-$ uptake systems have a reduced affinity for their substrates. The results suggest the existence of a $ycf10$-dependent system within the plastid envelope which promotes efficient inorganic carbon (Ci) uptake into chloroplasts.
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cea-04493738 , version 1 (07-03-2024)

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Norbert Rolland, Albert-Jean Dorne, Gabi Amoroso, Dieter F. Sültemeyer, Jacques Joyard, et al.. Disruption of the plastid $ycf10$ open reading frame affects uptake of inorganic carbon in the chloroplast of Chlamydomonas. EMBO Journal, 1997, 16 (22), pp.6713-6726. ⟨10.1093/emboj/16.22.6713⟩. ⟨cea-04493738⟩
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