BIOGENESIS OF PETUNIA AND CARNATION COROLLA CHLOROPLASTS - CHANGES INTHE ABUNDANCE OF NUCLEAR AND PLASTID-ENCODED PHOTOSYNTHESIS-SPECIFIC GENE-PRODUCTS DURING FLOWER DEVELOPMENT

To study the biogenesis of the photosynthetic apparatus in corollas, a s well as compositional differences between corolla and leaf chloropla sts, the levels of 12 nuclear- and plastid-encoded thylakoid and strom al components were analyzed by western blotting using heterologous ant isera. Relative levels of the thylakoid polypeptides analyzed in petun ia (Petunia hybrida cv. Hit Parade Rosa) and carnation (Dianthus caryo phyllus cv. White Sim) corollas increased, per unit chlorophyll, in pa rallel to corolla development, peaking at the mature stage in both flo wer types, with the exception of subunit V of the photosystem I (PSI) core complex, which continued to accumulate even after anthesis. The p hotosystem II (PSII) major light-harvesting chlorophyll a/b protein ac cumulated in corollas to a level, per unit chlorophyll, similar to tha t in leaves in both petunia and carnation plants. Components of the cy tochrome b6/f complex were found to accumulate to higher levels in cor olla chloroplasts than in leaves. The opposite trend was found for com ponents of the PSI core complex, as well as for the stromally located small and large subunits of ribulose-1,5-bisphosphate carboxylase, whi ch accumulated in corollas to levels ca 2.5 times lower than their res pective levels in leaves. The latter subunits accumulated coordinately in corollas of both plant types during flower development. Data obtai ned from immunological studies were correlated with those at the mRNA level. Northern blotting revealed that, in petunia corollas, the stead y-state transcript level of genes coding for the small subunit of ribu lose-1,5-bisphosphate carboxylase was identical to that of genes codin g for the major light-harvesting chlorophyll a/b protein. Levels of bo th transcripts, as well as those of plastid-encoded genes for the PSII reaction center's D1 and D2, were ca two-thirds of their respective l evels in leaves. In contrast, the level of transcript for the large su bunit of ribulose- 1,5-bisphosphate carboxylase was reduced 5-fold in petunia corollas, as compared to leaves.