Plastids are pivotal target organelles for comprehensively enhancing photosynthetic and metabolic traits in plants via plastid engineering. Plastid proteins are predominantly encoded by the nuclear genome, are made in the cytosol, and must traverse membrane-bound multiprotein translocons to access these organelles. This import process is meticulously regulated by chloroplast-targeting peptides (cTPs). Thagun et al. performed a comprehensive exploration and comparative assessment of an advanced suite of cTPs exhibiting superior targeting capabilities. They employed a multifaceted approach to identify and analyze 88 cTPs associated with Arabidopsis thaliana mutants with phenotypes linked to chloroplast function. A highly efficient cTP derived from Arabidopsis plastid ribosomal protein L35 (At2g24090) displayed remarkable effectiveness in chloroplast localization. This cTP could serve as an ideal transit peptide for precisely targeting biomolecules to plastids, leading to advancements in plastid engineering. The image shows four panels, each showing tobacco leaves expressing green fluorescent protein fused to a different cTPs (green). Chloroplasts are shown by chlorophyll autofluorescence (magenta).

Image Credit: Chonprakun Thagun and Keiji Numata