Time to pump iron: iron-deficiency-signaling mechanisms of higher plants

Iron is an essential nutrient for plants, yet it often limits plant growth. On the contrary, overaccumulation of iron within plant cells leads to oxidative stress. As a consequence, iron-uptake systems are carefully regulated to ensure that iron homeostasis is maintained. In response to iron limitation, plants induce expression of sets of activities that function at the root–soil interface to solubilize iron and subsequently transfer it across the plasma membrane of root cells. Recent advances have revealed key players in the signaling pathways that function to induce these iron-uptake responses. Transcription factors belonging to the basic helix–loop–helix, ABI3/VP1(B3), and NAC families appear to function either directly or indirectly in the upregulation of iron deficiency responses.