A dominant nuclear mutation in Chlamydomonas identifies a factor controlling chloroplast mRNA stability by acting on the coding region of the petA transcript

A. Boulouis , Y. Choquet, J. Girard-Bascou, K. Wostrikoff1, D. Drapier, R. Kuras, and F.A. Wollman

Laboratoire de Physiologie Membranaire et Moléculaire du Chloroplaste, UMR 7141 CNRS-UPMC Paris 6, IBPC, 13 rue Pierre et Marie Curie 75005 Paris 1Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY

We isolated a mutant strain of Chlamydomonas reinhardtii, su0, which is affected in the expression of the cytochrome b6f complex. It shows a 10-fold decrease in petA transcript accumulation when compared to the wild type. Crosses of the su0 mutant with wild type demonstrated the nuclear origin of the mutation. The study of su0/+ diploid strains showed that su0 is a dominant mutation. Using chimeric genes comprising different parts of the petA gene introduced by transformation into the chloroplast genome of the su0 strain, we showed that the mutated gene product in strain su0 acts on the petA coding sequence. Positional cloning of the su0 mutation indicated a tight linkage (less than 2cM) with the ZYS3 marker (LG XVI-XVII), which is also the marker showing the tightest linkage to the mutation mda1-ncc1, which has a similar phenotype but acts on the polycistronic chloroplast-encoded atpA transcript. We discuss the possible functional roles of these nucleus-encoded factors in the metabolism of chloroplast transcripts.

e-mail address of presenting author: boulouis@ibpc.fr