Molecular chaperone required for chloroplast biogenesis (PubMed:12943545, PubMed:25216779). Essential for chloroplast biogenesis and maintenance, and thus for embryogenesis (PubMed:23875936, PubMed:23382192). May be involved in the disassembly of VIPP1 for thylakoid membrane formation and/or maintenance (PubMed:23875936). Cooperates with TIC components and other molecular chaperones to drive transport of preproteins into chloroplasts and functions in the chloroplast stroma to facilitate membrane translocation during protein import into the organelle (PubMed:23382192). Homodimer (PubMed:25216779). Interacts with VIPP1 (PubMed:23875936). Interacts with P23-1 (PubMed:20493581). Expressed in roots, cotyledons, young leaves, mature leaves, stems, flowers, petals and siliques. During embryogenesis, highly expressed at 4 days post anthesis. By heat shock and light. Embryonic lethality due to embryo development arrest at the heart stage. Plants over-expressing HSP90.7 show albino and stunted leaves. Belongs to the heat shock protein 90 family.