The Arabidopsis gene () encodes a transcription factor that positively affects the activity of nuclear genes for chloroplast ribosomal proteins and chloroplast protein import machineries. () is the paralogous gene of . We generated a mutant by site-directed mutagenesis and compared it with and double mutant. Phenotype of the mutant did not differ from the wild type under our growth conditions, except faster growth and earlier time to flowering. Compared to , the mutant showed more impaired chloroplast functions and reduced amounts of plastid ribosomal RNAs. analyses predict for CIA2 and CIL a C-terminal CCT domain and an N-terminal chloroplast transit peptide (cTP). Chloroplast (and potentially nuclear) localization was previously shown for HvCMF3 and HvCMF7, the homologs of CIA2 and CIL in barley. We observed nuclear localization of CIL after transient expression in Arabidopsis protoplasts. Surprisingly, transformation of with , , or with a truncated lacking the predicted cTP could partially rescue the pale-green phenotype of . These data are discussed with respect to potentially overlapping functions between CIA2, CIL, and their barley homologs and to the function of the putative cTPs of CIA2 and CIL.