Chloroplast biogenesis is a highly complex process. Upon illumination undifferentiated proplastids differentiate into green chloroplasts with thylakoid membranes and a functional photosynthetic apparatus. This transition process is very rapid and, therefore, difficult to dissect. So far the molecular regulation and the protein dynamics during this transition process is not understood. The Arabidopsis albino mutant pap7-1 is used as a genetic tool to understand the early chloroplast biogenesis process. This mutant exhibits an arrested chloroplast biogenesis and down-regulated plastid transcription. The PAP7/pTAC14 protein has been identified as a subunit of the PEP complex but its function is still elusive. In order to obtain insights into the role of PAP7/pTAC14 we determined the proteome of the homozygous albino mutants and compared it to those of light-and dark-grown wild-type plants. The mass spec data were complemented by a western-immuno-blot assays. The preliminary results show that the protein accumulation follows the transcript accumulation. Rubisco does not accumulate in the pap7-1 mutant. The majority of the nuclear-encoded antenna proteins (LHCB1, LHCB3, LHCA2) were completely absent in pap7-1 mutant. While the water-splitting complex protein PSBO accumulated to normal levels indicating that import into albino plastids is functional. The genetic blocks of the pap7-1 mutant did not affect the accumulation of mitochondrial proteins. Comparable results were obtained in the proteomic results, however in most cases the changes at the protein level were much stronger than those at the transcript level.