A protochlorophyllide light-harvesting complex involved in de-etiolation of higher plants

When etiolated angiosperm seedlings break through the soil after germination, they are immediately exposed to sunlight, but at this stage they are unable to perform photosynthesis'. In the absence of chlorophyll a and chlorophyll b, two other porphyrin species cooperate as the basic light-harvesting structure of etiolated plants. Protochlorophyllide a and protochlorophyllide b (ref. 2) form supramolecular complexes with NADPH and two closely related NADPH:protochlorophyllide oxidoreductase (POR) proteins-PORA and PORE (ref. 3)-in the prolamellar body of etioplasts. Here we report that these light-harvesting POR-protochlorophyllide complexes, named LHPP, are essential for the establishment of the photosynthetic apparatus and also confer photoprotection on the plant. They collect sunlight for rapid chlorophyll a biosynthesis and, simultaneously, dissipate excess light energy in the bulk of non-photoreducible protochlorophyllide b. Based on this dual function, it seems that LHPP provides the link between skotomorphogenesis and photosynthesis that is required for efficient de-etiolation.