THE INFLUENCE OF EXOGENOUSLY SUPPLIED SPERMINE ON PROTOCHLOROPHYLLIDE AND CHLOROPHYLL BIOSYNTHESIS

The pigment mutant C-2A' of the unicellular green alga Scenedesmus obliquus synthesizes only protochlorophyllide and traces of chlorophyll in darkness. The reduction of protochlorophyllide to chlorophyllide and the synthesis of chlorophyll take place in the light. The tetramine spermine, contrary to the diamine putrescine and the triamine spermidine, regulates the amount of protochlorophyllide and chlorophyll in the dark and in the light. Low amounts of exogenous spermine induce chlorophyll biosynthesis (the optimum level is 0.32 mM SPM), while higher amounts inhibit chlorophyll biosynthesis. In the dark, spermine enhances the amount of accumulated protochlorophyllide, a fact that we attribute to inhibition of the light-independent protochlorophyllide oxidoreductase activity. Uptake measurements of spermine and its possible incorporation in prolamellar bodies/prothylakoids in comparison with the influence of spermine on chlorophyll biosynthesis allowed us to determine approximately and to discuss the likely role of spermine in the biosynthesis of photosynthetic pigments.