Cadmium interference with iron sensing reveals transcriptional programs sensitive and insensitive to reactive oxygen species

Abstract

Iron (Fe) is an essential micronutrient whose uptake is tightly regulated to prevent either deficiency or oxidative stress. Cadmium (Cd) is a non-essential heavy metal that induces both Fe-deficiency and oxidative stress; however, the mechanisms underlying these Cd-induced responses are still elusive. Here we explored Cd-induced Fe-associated responses in wildtype Arabidopsis and opt3-2, a mutant that over-accumulates Fe. Gene expression profiling revealed a large overlap between transcripts induced by Fe-deficiency and Cd exposure in wildtype plants and the opt3 mutant. Interestingly, vascular-localized Fe-responsive genes were found to be highly induced by Cd even in the presence of high Fe and H2O2 levels, suggesting that Cd impairs Fe sensing. It was recently shown that Fe-S cluster-containing proteins AtNEET, play a role in Fe sensing. Our data shows that Cd negatively impacts both the stability and Fe-S transfer activity of AtNEET. Altogether, our data indicate that Fe-deficiency responses are governed by multiple inputs and that a hierarchical regulation of Fe-deficiency responses prevents the induction of specific gene networks when Fe and H2O2 levels are high. Other Cd/Fe-responsive genes however, are insensitive to this negative feedback regulation suggesting that their induction is the result of an impaired Fe sensing as opposed to the traditional view of Cd/Fe uptake competition at the root level.Highlight Cadmium induces an iron-deficiency response often explained by root uptake competition; here we show that Cd also impairs Fe sensing in leaves, even when Fe is in sufficient quantities.Competing Interest StatementThe authors have declared no competing interest.View Full Text