Probably involved in the regulation of plastid gene expression. Component of the plastid transcriptionally active chromosome required for plastid gene expression (PubMed:16326926). Interacts with DEGP1 under high light conditions and maybe its degradation target (PubMed:21877139). Excluded from chloroplast nucleoid when phosphorylated on Thr-451 by STN7 that may regulate membrane-anchoring functions of the nucleoid. No visible phenotype and normal nucleoids. Belongs to the NAD(P)-dependent epimerase/dehydratase family.