GSE128156
Cadmium interference with iron sensing reveals transcriptional programs sensitive and insensitive to reactive oxygen species
Iron (Fe) is an essential micronutrient whose uptake is tightly regulated to balance both deficiency and Fe excess induced oxidative stress. The non-essential heavy metal cadmium (Cd) both induces oxidative stress and an Fe deficiency like response.  It is unclear how Cd induces this response, nor how it relates to Fe status sensing.  Using next generation sequencing, H2O2 quantification in both wild type and the Fe over-accumulating mutant opt3-2, we explored how Cd interferes with Fe sensing.  We found a large overlap of genes consistently responsive to Fe deficiency and Cd in both leaves and roots.  Two subnetworks emerged dependent on the high Fe and H2O2 concentration in opt3-2, while opt3-2 chloroplasts showed reduced photosynthetic efficiency during Cd exposure, indicating that they are one source of H2O2.  We describe the hierarchical regulation of Fe deficiency responses in the context of the opt3-2 mutant, and demonstrate that the opt3 dependent induction of Fe deficiency responses can be negated, or even reversed, by H2O2 dependent signaling, while the high Fe content of opt3-2 indicates Cd induced iron deficiency is not a function of reduced Fe uptake, but rather the putative leaf Fe sensor is Cd liable. Overall design: Wild type (Col-0) and opt3-2 were subjected or not to 20uM CdCl2 in hydroponic culture for 72hr.  mRNA from leaves and root were isolated seperately and sequenced on a Illumina Hiseq.  Three biological replicates were sequenced for each sample type.