Iron delivery to the growing leaves associated with leaf chlorosis in mugineic acid family phytosiderophores-generating graminaceous crops

Graminaceous cereal crops as well all other green plants require iron (Fe), Fe is a component of heme and [Fe-S] clusters in the photosystems (PSI, PSII) containing pigments (chlorophylls). The interveinal yellowing (Fe chlorosis) growing leaves caused by insufficient uptake internal delivery. In 1970s, Sei-ichi Takagi discovered Fe3+-chelating mugineic acid family phytosiderophores (MAs), which are released from graminaceous roots to directly absorb Fe-MAs complexes. However, mechanisms underlying delivery root cells terminal mesophyll need intensive investigation. This review first overviews roles metal-chelating compounds, i.e., MAs nicotianamine (NA), Fe-chelate transporters involved primary partitioning; then, via phloem into developing chloroplasts/thylakoids symplastic diffusion membrane transport discussed. absorbed epidermis YSL transformed Fe-NA for radial movement between parenchyma xylem. If heavy metal ions such Co2+ Cu2+ simultaneously present, competition may occur at their complex formation with NA prior that causes leaf chlorosis because metal-induced restriction availability. xylem saps, large fractions form Fe-MAs, barley (Hordeum vulgaris), instead Fe-citrate, predominant rice (Oryza sativa). former complexes transferred stem nodes leaves, while Fe-citrate partitioned mature transpiration. Although major routes supply have been confirmed, synthesis Fe-compounds, through system, unloading sink trafficking utilization still Thus, finally chloroplasts cause reduced chlorophyll?Fe-protein assembly (chlorosis). schemes presented this must be confirmed future studies.