Alteration of iron responsive gene expression in Arabidopsis glutaredoxin <i>S17</i> loss of function plants with or without iron stress

Iron (Fe) is a mineral nutrient and a metal cofactor essential for plants. Iron limitation can have detrimental effects on plant growth and development, while excess iron inside plant cells leads to oxidative damage. As a result, plants have evolved complex regulatory networks to respond to fluctuations in cellular iron concentrations. The mechanisms that regulate these responses however, are not fully understood. Heterologous expression of an <i>Arabidopsis thaliana</i> monothiol glutaredoxin S17 (GRXS17) suppresses the over-accumulation of iron in the <i>Saccharomyces cerevisiae</i> Grx3/Grx4 mutant and disruption of <i>GRXS17</i> causes plant sensitivity to exogenous oxidants and iron deficiency stress. GRXS17 may act as an important regulator in the plant’s ability to respond to iron deficiency stress and maintain redox homeostasis. Here, we extend this investigation by analyzing iron-responsive gene expression of the Fer-like iron deficiency-induced transcription factor (FIT) network (<i>FIT, IRT1, FRO1</i>, and <i>FRO2</i>) and the bHLH transcription factor POPEYE (PYE) network (<i>PYE, ZIF1, FRO3, NAS4</i>, and <i>BTS</i>) in <i>GRXS17</i> KO plants and wildtype controls grown under iron sufficiency and deficiency conditions. Our findings suggest that GRXS17 is required for tolerance to iron deficiency, and plays a negative regulatory role under conditions of iron sufficiency.