Abstract
Graminacious plants secrete mugineic acid family phytosiderophores (MAs) from their roots to solubilize the external insoluble iron and absorb the chelated iron. The secretion of MAs from root increases under Fe-deficient condition and followed the circadian rhythm. The particular vesicles derived from rER were observed to accumulate at the cell periphery near the cell membrane in Fe-deficient barley roots before sunrise. Immunocytochemical analysis on nicotianamine synthase (NAS), nicotianamine aminotransferase (NAAT), deoxymugineic acid synthase (DMAS) and IDS3, enzymes in MAs biosynthesis pathway, revealed that these enzymes were induced in Fe-deficient root epidermal cells. The subcellular localization of NAS and NAAT were determined to be on the membrane and inside of vesicle, respectively. DMAS and IDS3 were localized to the vicinity of the vesicle. We concluded that this particular vesicle could be related to the MAs synthesis. The polar vesicle transport may regulate the diurnal rhythm of MAs secretion from barley roots.
