The abundance of Cab and psbA transcripts and of their products in greening etiolated leaves transferred to darkness

摘要

The growth of the photosynthetic membrane depends on coordinated synthesis and assembly of nuclear-coded and plastid-encoded proteins. An example of such a control of coordinated expression is that of Photosystem II; the reaction center (RC) proteins D1/D2) are synthesized in the chloroplast and are cotranslationally inserted in the membrane, whereas the surrounding Light-harvesting (LHC) proteins are synthesized in the cytoplasm and after processing of the transit sequence they are imported in the organelle and anchored in the membrane as a lipophilic complex via Chl binding. On the other hand, the photosynthetic membrane is a dynamic system which responds to the changing environmental conditions with a number of control mechanisms directed not only to the transcriptional and translational level, but most important to the posttranslational level. Such a post translational control is evident at the early stages of greening where new PS units are still beeing formed. At these early stages a developmentally regulated thylaklid-bound protease degrades LHCs when not rescued by Chl binding.