plastid transcriptomics and translatomics of tomato fruit development and chloroplasttochromoplast differentiation chromoplast gene expression largely serves the production of a single protein plastid genes are expressed at high levels in photosynthetically active chloroplasts but are generally believed to be drastically downregulated in nongreen plastids the genomewide changes in the expression patterns of plastid genes during the development of nongreen plastid types as well as the contributions of transcriptional versus translational regulation are largely unknown we report here a systematic transcriptomics and translatomics analysis of the tomato solanum lycopersicum plastid genome during fruit development and chloroplasttochromoplast conversion at the level of rna accumulation most but not all plastid genes are strongly downregulated in fruits compared with leaves by contrast chloroplasttochromoplast differentiation during fruit ripening is surprisingly not accompanied by large changes in plastid rna accumulation however most plastid genes are translationally downregulated during chromoplast development both transcriptional and translational downregulation are more pronounced for photosynthesisrelated genes than for genes involved in gene expression indicating that some lowlevel plastid gene expression must be sustained in chromoplasts highlevel expression during chromoplast development identifies accd the only plastidencoded gene involved in fatty acid biosynthesis as the target gene for which gene expression activity in chromoplasts is maintained in addition we have determined the developmental patterns of plastid rna polymerase activities intron splicing and rna editing and report specific developmental changes in the splicing and editing patterns of plastid transcripts