Regulation of chloroplast biogenesis and differentiation

Chloroplasts are semi-autonomous organelles essential for photosynthetic organisms. They derived from ancestral cyanobacteria through an endosymbiotic event. In plants, these organelles are inherited as non-photosynthetic plastids, the proplastids, which can differentiate into chloroplasts or other specialized types of plastids in response to external and internal signals and cues, and following precise developmental programmes. Transcriptional regulation of chloroplast biogenesis and, to a lesser extent chromoplast differentiation, has been a central focus of interest, leading to the identification of several key factors. This review highlights recent research on transcription factors and epigenetic modifiers that regulate chloroplast biogenesis, the evolution of transcriptional regulation in land plants, and factors regulating chromoplast differentiation. However, significant knowledge gaps remain regarding plastid differentiation in specific tissues and species, as well as the biogenesis of other plastid types. Thus, the review highlights the complexity of chloroplast biogenesis, and open questions on spatial and temporal regulation, lineage- and species-specific mechanisms, and biogenesis of diverse plastid types. Understanding this process will advance basic plant biology but also holds biotechnological potential to address present and future challenges.