Abstract
Nicotianamine synthase(NAS) is an enzyme essential for all the higher plants. Three nas genes (zmnas) were isolated from maize and characterized. Interestingly, ZmNAS2 protein contained a partially repeated NAS sequence. zmnas1 and zmnas2 were expressed only in roots and their expression was induced by Fe-deficiency. On the other hand, zmnas3 was constitutively expressed in leaves and its expression was suppressed by Fe-deficiency. This pattern of nas expression was reported for the first time here. Western blot analysis revealed that ZmNAS1 and ZmNAS2 were the major NAS in Fe-deficient maize roots. In vitro asssy revealed that ZmNAS1 and ZmNAS3 had NAS activity but that ZmNAS2 did not. In onion epidermal cells, ZmNAS1-GFP and ZmNAS2-GFP were observed as spots in cytoplasm, whereas ZmNAS3-GFP was located in cytoplasm entirely. These differences in their property suggest that nicotianamine synthesized by each NAS has different roles in maize.
