CHANGES IN THE BIOSYNTHESIS AND CATABOLISM OF POLYAMINES IN ISOLATED PLASTIDS DURING CHLOROPLAST PHOTODEVELOPMENT

Polyamines (PAs), diamine oxidase (DAO) activity and putrescine format ion via ornithine (ornithine decarboxylase, ODC) and arginine (arginin e decarboxylase and arginase pathway, ADC) were found in isolated eti oplasts, chloroplasts and the intermediate plastids of chloroplast pho todevelopment. The isolated etioplasts contain large amounts of PAs (p utrescine (Put), spermidine (Spd), spermine (Spm)), and high activitie s of the main PA biosynthetic enzymes ODC and ADC, combined with very low activity of the main PA catabolic enzyme DAO, were found. During the photodevelopment of etioplasts to chloroplasts, a two-step decreas e of intraplastidic PAs, ODC and ADC takes place: the first very fast and the second stronger after a very long exposure to light. The corr elation of these two steps with the protochlorophyllide (PChlide) to c hlorophyllide (Chlide) photoconversion and the development of the phot osynthetic apparatus is discussed. Our experiments indicate that the a lmost zero DAO activity in etioplasts increases rapidly and shows a ma ximum after exposure to light for 9 h, whereas the intracellular DAO a ctivity remains almost unchanged. All the plastidic activities (ODC, A DC, DAO) and the level of PAs (Put, Spd, Spm) during the photodevelop ment of chloroplasts are correlated with the corresponding intracellul ar values and the differences are discussed.