EVOLUTION OF INDOLE AND BENZOXAZINONE BIOSYNTHESIS IN Zea mays

摘要

Planl secondary metabolites constitute a large field of chemical biodiversity, The occurrence of certain metabolites in species sometimes reflects their phylogcnetic origin. On the other hand, closely related plant taxa often differ in their spectra of secondary products. The evolution of the synthetic capacity for these substances has accompanied plants from their origin onwards. In Arabidopsis thaliamh it is estimated that about 5,000 genes, i.e., about 20% of all genes, are involved in secondary metabolism.1 This may partly explain the relatively high number of genes present in plant genomes, when compared with genomes of mammals. Primary metabolism represents the platform from which secondary metabolism has evolved. Therefore, many of the "secondary metabolic" genes that encode enzymes or regulatory proteins have probably been recruited from genes encoding primary functions. In order to understand the evolution of secondary metabolism, we have to identify the genes specific for secondary metabolic pathways, determine their function, and try to reconstruct their origins from primary metabolism by sequence and functional comparisons with putative ancestral genes. Ongoing genome projects will be indispensable in this respect.