Interaction of Nuclear and Chloroplast Mutations in Biogenesis of Chloroplast Ribosomes in Chlamydomonas

Abstract

In Chlamydomonas, as in higher plants, the chloroplast genome codes for chloroplast ribosomal RNAs, tRNAs, about 1/3 of the ribosomal proteins, and a number of proteins of the photosynthetic apparatus (Table 1, Fig. 1). Other proteins are coded by the nuclear genome and imported, generally as precursors which are processed to mature form within the chloroplast (Table 1). Because C. reinhardtii can dispense with photosynthetic functions if provided acetate as an alternative carbon source, this species is an ideal model system for investigation of mutations affecting these components. In the case of the large subunit of ribulose bisphosphate carboxylase (RUBISCO; Spreitzer & Ogren, 1985), the 32 kd herbicide binding protein (Erickson et al., 1985), and the beta subunit of the CF₀CF₁ ATPase (Woessner et al., 1986), analysis of chloroplast genes has extended to the DNA sequence level, and to comparison of mutations and reversions within the same gene.