Molecular aspects of iron nutrition in plants

The plant kingdom comprises 766 gymnosperms and ~350,000 angiosperms, for which iron (Fe) is an essential and highly demanded nutrient. Iron is necessary for plant growth and development, being involved in a multitude of functions within the plant, including chlorophyll biosynthesis. The understanding of the mechanisms that govern Fe uptake, transport and storage has been the subject of numerous studies since the middle of the twentieth century, but it was only in the 1990s, with the advent of molecular genetics, cheaper genome sequencing and associated bioinformatic techniques, that scientists began to really unveil the detailed molecular networks responsible for regulating iron homeostasis within the plant. Homeostasis must be guaranteed in order to prevent Fe overload and toxicity but also to assure sufficient levels within the plant to exert its numerous roles, since the unalike consequences of both deficiency and toxicity are equally adverse. In this chapter we explore the current knowledge on the different molecular aspects that regulate Fe metabolism in higher plants, looking at Fe uptake and distribution mechanisms, the known signalling molecules and Fe sensing mechanisms, the part of Fe in plant-bacteria symbiosis (including nodulated and non-nodulated plants) and finally, how the molecular aspects of Fe metabolism impact and are impacted by other metals.