Required for photosynthetic protein complex assembly in chloroplast thylakoid membranes during leaf development (PubMed:27585744). Maintains the abundance of the core protein complex PsaA-PsaB of photosystem I (PSI) in the thylakoid membrane (PubMed:27585744). May play a role in the efficient biogenesis of the chloroplast ATP synthase complex, possibly by interacting with the beta subunit atpB (PubMed:27585744). Interacts with atpB. Highly expressed in leaves (PubMed:27585744). Expressed in leaf sheaths (PubMed:27585744). Expressed at low levels in stems (PubMed:27585744). Induced by light in dark-grown seedllings. Yellow-leaf phenotype due to reduced chlorophyll content. Truncated N-terminus.