Function Of The Maize Zinc-regulated Transporters,Iron-regulated Transporter-like Protein(ZIP5)in Maize

Zinc(Zn)and iron(Fe)are essential micronutrients for plant growth.Thus,it is important to understand the mechanisms of uptake,transport,and accumulation of these micronutrients in maize to improve crop nutritional quality.Members of the zinc-regulated transporters,iron-regulated transporter-like protein(ZIP)family are responsible for the uptake and transport of divalent metal ions in plant.Previously,we showed that ZmZIP5 functionally complemented the Zn uptake double mutant zrtlzrt2,Fe-uptake mutantfet3fet4 in yeast.In our ?-glucuronidase(GUS)assay,the germinated seeds,young sheaths,and stems of ZmZ/P5-promoter-GUS transgenic plants were stained.We generated and compared two maize lines for this study:Ubi-ZmZIP5,in which ZmZIP5 was constitutively overexpressed,and ZmZIP5i,a RNAi line.At the seedling stage,high levels of Zn and Fe were found in the roots and shoots of Ubi-ZmZIP5 plants,whereas low levels were found in the ZwmZIP5i plants.Zn and Fe contents decreased in the seeds of Ubi-ZmZIP5 plants and remained unchanged in the seeds of ZmZIP5i plants.The seeds of Leg-ZmZIP5 plants,in which ZmZIP5 overexpression is specific to the endosperm,had higher levels of Zn and Fe.Our results imply that ZmZIP5 may play a role in Zn and Fe uptake and root-to-shoot translocation.Endosperm-specific ZmZIP5 overexpression could be useful for Zn and Fe biofortification of cereal grains.