Studies on Sporopollenin Biosynthesis in Cucurbita maxima (DUCH.) — II. The Involvement of Aliphatic Metabolism

Summary Due to the results of spectroscopic analysis, an involvement of aliphatics in the structure of the sporopollenin molecule has been proposed. To test this assumption on a biochemical level, tracer experiments were carried out in which the alifhatic moiety of the biopolymer was targeted. Tracer experiments were focussed on the incorporation of 14 C-labeled substances, such as acetic acid, malonic acid, stearic acid, oleic acid and linoleic acid. Several cofactors and inhibitors of sterol biosynthesis were used to enhance the incorporation rates of the precursors. The highest incorporation rates were obtained with acetic acid in the presence of a sterol biosynthesis inhibitor. The incorporation of this precursor could be increased to a significant extent if AMO 1618 was added simultaneously with the tracer. In the case of fatty acid the best results were obtained with oleic and stearic acids. With the significant incorporation of these substances the involvement of the aliphatic metabolism in biosynthesis of sporopollenin could be verified.