Required for proper chloroplast development, most likely through regulating plastid-encoded polymerase (PEP) dependent chloroplast transcription. Acts as a component of the transcriptionally active plastid chromosome that is required for plastid gene expression. Interacts with CITRX/TRXz (PubMed:20511297). Binds to FLN1 and PTAC5. Associates with the plastid-encoded RNA polymerase (PEP) complex (PubMed:24019900). Plants display chlorosis prior to leaf expansion, but exhibit slow greening, remain autotrophic, can grow to maturity, and set viable seed (PubMed:22770232). Albino phenotype of seedlings grown on sucrose-free medium associated with reduced plastid-encoded RNA polymerase (PEP)-dependent gene expression and altered chloroplast development. Delayed greening of seedlings grown on sucrose-containing medium (PubMed:24019900). RNAi plants display abnormal plastids lacking internal membrane structures. Belongs to the carbohydrate kinase PfkB family.