GmVIT1: a ferrous iron transporter on the Glycine max symbiosome membrane is essential for nitrogen fixation

EM Brear1, A Gavrin1, DA Barton1, Y Qu1, DA Day2 and PMC Smith1

  1. The University of Sydney
  2. Flinders University

Iron is essential for symbiotic nitrogen fixation. It is required by the bacteroid for the production of nitrogenase and enzymes of the respiratory chain, and for the synthesis of leghemoglobin. Although the nodule has a high demand for iron the pathways for iron transport, particularly into the symbiosome are not clear. GmVIT proteins are members of the vacuolar iron transporter family, which transport ferrous iron into the vacuole in Arabidopsis and yeast. Based on the orientation of the symbiosome membrane (SM) they are standout candidates for facilitating ferrous iron transport into the symbiosome. GmVIT1 is expressed in the mature nodule, predominantly in infected cells. In the infected cell, GmVIT1 localises to the SM and its ability to complement the yeast vacuolar iron transport mutant Δccc1, suggests it transports ferrous iron across the SM. In addition, its ability to restore nitrogen fixation, when expressed in the L. japonicus mutant, sen1, highlights that it is essential for the symbiosis and that LjSEN1 may also transport ferrous iron.