RNA-binding protein that acts as an RNA chaperone to remodel RNA structure and activates their translation. Required for seed pigmentation. Necessary for chloroplast development and subsequent photosynthetic electron flow, as well as for non-photochemical quenching (NPQ). Rubisco regulatory factor which regulates the concerted biogenesis of NDH, PSI (including PsaA, PsaB, PsaD, PsaF, PsaL, PsaG, PsaK and NdhH) and Cytb(6)f (including PetA, PetB, PetC and PetD) complexes. Binds specifically to and involved in the post-transcriptional regulation of plastid-encoded mRNAs (e.g. rbcL, petA, petB, petD and Ycf1), thus modulating expression, cellular localization/compartmentalization, and photosynthetic function