Biosynthesis and biological role of polyamine conjugates in flowers of Arabidopsis thaliana

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Polyamine conjugates are described as flower constituents of many plant species. Recent evidence from Arabidopsis suggests that the precise substitution pattern of these conjugates may be required for anther development or be essential for pollen grain maturation and germination. These assumptions are based on the identification of a novel tapetum-specific, cation-dependent caffeoyl coenzyme A O-methyltransferase (CCoAOMT)- like protein, AtTSM1, involved in the decoration of Arabidopsis specific phenylpropanoid polyamine conjugates. Clustering of the AtTSM1-gene with several anther specific genes and the phenolic profiling pattern of the corresponding knockout lines demonstrate the association of at least three other genes in the biosynthesis of these conjugates. The resulting amides were identified as the predominant constituents in the soluble portion of Arabidopsis pollen where they play a currently unknown role in pollen ultrastructure or development. With this proposal we aim to characterize the relevant genes and biosynthetic enzymes associated with this pathway, determine the polyamine conjugate pattern of Arabidopsis and related Brassicaceae in flowers and pollen, to clarify the biological role of these universal, yet poorly understood metabolites in pollen grain maturation and successful seed set.