Iron transport, deposition and bioavailability in the wheat and barley grain

In recent years, the increasing knowledge on the molecular mechanisms underlying mineral uptake, transport, homeostasis and deposition within plants, has paved the way for a more targeted approach to improving the nutrient status of crop plants based on biotechnology. In the present paper we will briefly review existing knowledge on the distribution and transport pathways of iron in the two small grained cereals, barley and wheat, and focus on the efforts made to increase the iron content in cereals in general. However, mineral content is not the only factor of relevance for improving the nutritional status of poor populations. It is thus well documented that a number of plant components can act either as promoters or inhibitors of mineral uptake in the human digestive system (Frossard et al. J Sci Food Agric 80, 817-879 2000; Brinch-Pedersen et al. J Cereal Sci 46, 308-326 2007). The nutritional impact of increasing mineral content accordingly has to be seen in the context of mineral bioavailability. Finally, we will briefly report on recent data from barley, where laser capture microdissection of the different grain tissues combined with gene expression profiling has provided some insight into metal transport and deposition (Tauris et al. 2009). In the present paper we will provide a tentative and preliminary roadmap for iron trafficking in the barley grain.