Determinants for stability of the chloroplast psbD RNA are located within its short leader region in Chlamydomonas reinhardtii.

Stability of the chloroplast psbD mRNA encoding the D2 protein of the photosystem II reaction center is drastically decreased in the nuclear photosynthetic mutant nac2-26 of Chlamydomonas reinhardtii. Using biolistic transformation and genetic crosses we have introduced chimeric genes consisting of the psbD leader fused to a reporter gene into the chloroplast in both wild-type and mutant nuclear backgrounds. The chimeric message is destabilized in the latter, but not in the former case, indicating that the 74 nt psbD leader includes one of the target sites for psbD RNA degradation in the absence of wild-type NAC2 function.

Mutation at the Chlamydomonas nuclear NAC2 locus specifically affects stability of the chloroplast psbD transcript encoding polypeptide D2 of PS II.

The nuclear NAC2 locus of C. reinhardtii encodes a trans-acting factor that confers stability on the chloroplast message for the D2 protein of photosystem II (PS II). A mutant that carries a lesion in the NAC2 gene is unable to accumulate the psbD transcript encoding D2, but synthesizes all other PS II proteins normally.

Construction and characterization of autonomously replicating plasmids in the green unicellular alga Chlamydomonas reinhardii.

Plasmids that replicate autonomously in Chlamydomonas reinhardii were constructed by inserting random DNA fragments from this alga into a plasmid containing the yeast ARG4 locus. Arginine prototrophy was used as a selective marker. The presence of free plasmids in the DNA of the transformants was demonstrated by hybridization with a specific plasmid probe and by recovering these plasmids in E.