PROTOCHLOROPHYLLIDE OXIDOREDUCTASE AND CHLOROPHYLL BIOSYNTHESIS IN GREENING BARLEY SEEDLINGS

The content and extent of photodestruction of NADPH:protochlorophyllid e oxidoreductase (PCR) as well as chlorophyll accumulation after illum ination in barley (Hordeum vulgare L.) seedlings were determined as de pendent on the length of etiolation period. The PCR content was tested by immunoassay. In the etiolated seedlings, we observed an age-depend ent increase in PCR content and the enrichment of the PCR photoactive complex with protochlorophyllide (PChlde) in the fraction of prolamell ar bodies from the first leaf. Such an etiolated leaf also exhibited a n age-dependent enhancement of enzyme photodestruction under illuminat ion (3500 1x, 3.5 h) and a decrease in both the rate and level of chlo rophyll accumulation. In the coleoptiles of etiolated seedlings, incap able of synthesizing the PChlde, a protein identical to PCR and nonres istant to photodestruction was found. At the same time, PCR was detect ed in the leaves and coleoptiles of plants greening under the light (1 6 h)/darkness (8 h) regime. Chlorophyll biosynthesis is suggested to b e controlled only by PCR integrated into the multienzyme system partic ipating in pigment biosynthesis; such a system is assembled under illu mination and protects the PCR against photodestruction. Such a possibi lity of PCR integration into this system declines with etiolation time and depends on the type of plastid biogenesis.