Essential protein involved in plastid gene expression (PubMed:16326926, PubMed:31128276). Recruited by MTERF5 to the transcriptionally paused region of psbEFLJ (PubMed:31128276). Promotes leaf greening (PubMed:24272250). Subunit of the plastid-encoded RNA polymerase (PEP) complex (PubMed:16326926, PubMed:31128276). Interacts with MTERF5 (PubMed:31128276). Mostly expressed in rosette leaves, stems and flowers, and, to a lower extent, in roots and cauline leaves. Lethal without exogenous carbon sources (PubMed:16326926). Reduced expression of plastid-encoded genes with plastid-encoded multimeric promoters (PEP) (PubMed:16326926, PubMed:31128276). Strongly reduced presence of both plastid- and nuclear-encoded soluble polypeptides and polypeptides associated with the thylakoid membrane in chloroplasts (PubMed:16326926). Albino plants unable to produce primary leaves white cotyledons that fails to accumulate chlorophyll (Chl) even in low light, thus leading to high nonphotochemical quenching (NPQ) (PubMed:16326926, PubMed:24272250). Abnormal chloroplasts which fail to contain grana thylakoids that are replaced by oval-shaped vesicles surrounded by plastoglobuli (PubMed:16326926). Starch accumulates only in old leaves (PubMed:16326926).