Plays an essential role in early steps of chloroplast development. May be involved in the redox control of plastid gene expression by maintening the redox state around chloroplast nucleoids. May positively regulate plastid-encoded RNA polymerase (PEP) activity, through binding to FSD2. Interacts with FSD2 and MRL7. Highly expressed in young leaves, shoots and flowers. Expressed at low levels in stems and siliques. Induced by light. Seedling lethality due to deficiency in chloroplast development.