Isolation and Characterization of a Chlamydomonas reinhardtii Mutant Lacking the 7-Subunit of Chloroplast Coupling Factor 1 (CF₁)

Abstract

Several nonphotoautotrophic mutants of Chlamydomonas reinhardtii were generated by transforming strain nit1-305 (cw 15) with exogenous DNA. An enrichment for potential photophosphorylation mutants was performed on medium containing arsenate, and acetate-requiring auxotrophs were then identified by replica plating. Strains containing a potential mutation in the nuclear DNA encoding the chloroplast coupling factor 1 (CF₁) γ-subunit (the atpC gene) were first identified serologically with a monospecific antiserum directed against the CF₁ γ-subunit polypeptide. Of several mutants isolated, one, designated T1-54, was characterized at the protein, DNA, and RNA levels. Mutant strain T1-54 lacks anti-CF₁ γ-subunit cross-reacting material, exhibits polymorphism at the atpC locus compared with the parental strain, and lacks the mRNA transcript for the CF₁ γ-subunit. The data are consistent with there being an insertion of exogenous DNA, a deletion of DNA, or both at the 5′ end of the gene encoding the CF₁ γ-subunit.