Identification and characterization of an endogenous cytometallophore of general distribution in plants

Normal growth and development of higher plants is dependent on the presence of small amounts of a compound which seems to be of general distribution in the plant kingdom, at least in vascular plants. This_compound was shown to possess the structure (25:3'S:3"S)-N--L N—(3-amino-3—carboxypropyl)-3amino-3_carboxypropyi7-azetidine-2-carboxylic acid (1) and proved to be identical with nicotianamine. The only plant until yet known showing a block in the biosynthesis of nicotianamine is the monogenic, semi-lethal mutant 'chloronerva' of the tomato Lycopersicori esculenturn Mill. which is completely normalized restoring the phnotype of the original tomato wild— type by exogenous application of 1 demonstrating the general significance of this unique non-proteinous amino acid. Nico— tianamine possesses an optimal molecular structure for chelating iron(II) and other bivalent transition—metal ions (e. g. Cu, Ni, Go, Zn, and Mn). The optical antipode of 1, the (÷)-nico— tianamine as well as a number of structurally related compounds have been synthesized and their activity as "normalizing factor" for the mutant 'chloronerva' investigated. According to our present knowledge, nicotianamine is considered to be a specific cytometallophore with an essential function in the cellular transport and metabolism of bivalent transition—metal ions in plants, however not only as carrier but also as regulator of these and other processes.