Formation of Chlorophyll-Protein Complexes during Greening 1. Distribution of Newly Synthesized Chlorophyll among Apoproteins

The relationship between the accumulation of Chi and the apoproteins of the light-harvest-ing Chi a/6-protein complex of PS II (LHCII) during the greening of cucumber cotyledons was studied. LHCII apoproteins were not detected in etiolated cotyledons. Upon illumination, Chi a was formed as a result of photoconversion of protochlorophyllide (Pchlide) which had ac-cumulated in the dark. During the lag period that preceded the accumulation of Chi, a small amount of LHCII apoproteins appeared. The amount of LHCII apoproteins increased with in-creases in levels of Chi b, though somewhat more rapidly during the first 10 h of greening. Treat-ment with benzyladenine (BA) or levulinic acid (LA) was used to vary the supply of Chi a for apoproteins by promoting or inhibiting the synthesis of Chi a, respectively. LA decreased but BA increased the rate of accumulation of Chi b and LHCII apoproteins. Only small amounts of Chi b and LHCII apoproteins were formed under intermittent illumination. However, in the presence of chloramphenicol (CAP), which inhibits the synthesis of plastome-coded proteins in-cluding apoproteins of the P700-Chl o-protein complex (CPl) and a Chlfl-protein complex of PS II (CPa), we observed the accumulation of Chi b and LHCII apoproteins, both of which are of nuclear origin. During incubation in the dark after intermittent exposure to light, CAP alon