Nicotianamine synthase:: Gene isolation, gene transfer and application for the manipulation of plant iron assimilation

Basic cellular processes such as electron transport in photosynthesis and respiration require the precise control of iron homeostasis. To mobilise iron, plants have evolved at least two different strategies. The non-proteinogenic amino acid nicotianamine is an essential component of both pathways. We briefly review the characterisation of the nicotianamine synthase as a member of a novel class of enzymes, the cloning of the corresponding gene coding sequences of barley, Arabidopsis and tomato as well as the molecular basis of the chloronerva mutant exhibiting severe defects in the regulation of iron metabolism. Further, we report on current experiments aiming to the application of various NAS-genes to manipulate iron assimilation in model and crop plants using transgenic sense and antisense approaches.