Functional expression of MxIRT1, from Malus xiaojinensis, complements an iron uptake deficient yeast mutant for plasma membrane targeting via membrane vesicles trafficking process

Iron is an essential element for plants. But little is known about iron homeostasis in fruit trees. Malus xiaojinensis Cheng et Jiang is an iron-efficient genotype in the genus Malus. A cDNA clone, MxIRT1, was isolated from a library constructed from roots of M. xiaojinensis Cheng et Jiang under iron-deficient conditions. MxIRT1 is highly homologous to other iron-regulated transporters belonging to the ZIP family. Transcript level analyses indicated that the expression of MxIRT1 was strongly enhanced in roots under iron limitation. MxIRT1 could complement iron uptake activity of Saccharoomyces cerevisiae mutant strain DEY1453 (fet3fet4). The expression of MxIRT1::GFP protein in transformed yeast cells indicated that MxIRT1 was targeted into the plasma membrane through a protein trafficking processes via membrane vesicles under iron limitation. These results indicate that MxIRT1 is a component of iron homeostasis in M. xiaojinensis.