• mRNA processing;
  • nonphotosynthetic mutants;
  • thylakoid;
  • translation

The biogenesis of chloroplasts is genetically complex, involving hundreds of genes distributed between the nucleus and organelle. In higher plants, developmental parameters confer an added layer of complexity upon the genetic control of chloroplast biogenesis: the properties of plastids differ dramatically between different cell types. While the biochemistry and structure of different plastid types have been described in detail, factors that determine the timing and localization of chloroplast development and that mediate chloroplast assembly have remained elusive. To identify nuclear genes that play novel roles in chloroplast biogenesis, we are exploiting nuclear mutations that block the accumulation of subsets of chloroplast proteins. Detailed study of the mutant phenotypes provides clues concerning the primary defect in each mutant. Mutants with defects in chloroplast translation and mRNA metabolism have been identified. Other mutants defective in the accumulation of multiple thylakoid complexes show no apparent defect in the synthesis of the missing proteins. These may identify factors involved in the integration of proteins into the thylakoid membrane and their assembly into functional complexes.