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

When etiolated angiosperm seedlings break through the soil after germinatio n, they are immediately exposed to sunlight, but at this stage they are una ble to perform photosynthesis'. In the absence of chlorophyll a and chlorop hyll b, two other porphyrin species cooperate as the basic light-harvesting structure of etiolated plants. Protochlorophyllide a and protochlorophylli de b (ref. 2) form supramolecular complexes with NADPH and two closely rela ted NADPH:protochlorophyllide oxidoreductase (POR) proteins-PORA and PORE ( ref. 3)-in the prolamellar body of etioplasts. Here we report that these li ght-harvesting POR-protochlorophyllide complexes, named LHPP, are essential for the establishment of the photosynthetic apparatus and also confer phot oprotection on the plant. They collect sunlight for rapid chlorophyll a bio synthesis 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 photosynth esis that is required for efficient de-etiolation.