Ontogenetic, Light, and Circadian Regulation of PAP Protein Genes during Seed Germination of Arabidopsis thaliana.

The expression profiles of the PAP genes, encoding proteins associated with plastid multisubunit RNA polymerase, were studied in dry seeds, during germination, and at the early stages of Arabidopsis thaliana seedling formation. A detailed analysis of the PAP transcript levels by RT-PCR showed that the transition of seeds from dormancy to active growth is accompanied by a drastic increase in the transcript accumulation of all studied genes on the first day of germination, both in the light and in the dark. Further changes in transcript levels differed among PAP genes and were apparently determined by their functional specificity. It was established for the first time that the expression of individual PAP genes is regulated by circadian rhythms, in addition to factors of ontogenetic and light nature.