Changes in the biosynthesis and catabolism of polyamines in isolated plastids during chloroplast photodevelopment

Polyamines (PAs), diamine oxidase (DAO) activity and putrescine formation via ornithine (ornithine decarboxylase, ODC) and arginine (arginine decarboxylase and arginase pathway, ADC*) were found in isolated etioplasts, chloroplasts and the intermediate plastids of chloroplast photodevelopment. The isolated etioplasts contain large amounts of PAs (putrescine (Put), spermidine (Spd), spermine (Spm)), and high activities 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 decrease of intraplastidic PAs, ODC and ADC* takes place: the first very fast and the second stronger after a very long exposure to light. The correlation of these two steps with the protochlorophyllide (PChlide) to chlorophyllide (Chlide) photoconversion and the development of the photosynthetic apparatus is discussed. Our experiments indicate that the almost zero DAO activity in etioplasts increases rapidly and shows a maximum after exposure to light for 9 h, whereas the intracellular DAO activity remains almost unchanged. All the plastidic activities (ODC, ADC*, DAO) and the level of PAs (Put, Spd, Spm) during the photodevelopment of chloroplasts are correlated with the corresponding intracellular values and the differences are discussed.