The first green: assembly of quantum traps in higher plant plastids

Abstract

If not strictly controlled, chlorophyll (CHL) may work as a hazardous photooxidant in the oxigenic surrounding of a living cell. Biogenesis of the functional chlorophyll bearing photosynthetic quantum traps is therefore a strictly regulated matter throughout in nature. Plants grown in complete darkness still develop a quantum trap, protochlorophyllide oxidoreductase (POR), and structural biogenesis of photosynthetic quantum traps is started. POR regulates phototransformation of the chlorophyll precursor educt and the availability of the enzymatic product chlorophyllide for final esterification with geranylgeranylpyrophosphate by Chl-synthase. Chlorophyll then strictly controls functional biogenesis of photosynthetic reaction centers and core complexes and light harvesting complexes. Etioplasts isolated from barley seedlings are used as a model system to demonstrate by time resolved spectroscopic and electrophoretic techniques how photoreduction, esterification and photosystem assembly are coordinated and regulated. The high resolution for separation of membrane proteins now enables us to investigate the potential role of assembly regulators during photosystem biogenesis.