Dynamic Changes in Ion Accumulation and Gene Expression Reveal Root-Specific Iron Uptake Strategies in Iron-Deficient Rice after Supplementation

Exploring the biological processes of iron homeostasis aids in understanding crop genetic improvement to combat human malnutrition. This study employs phenotyping, ionomics, and transcriptome analysis to reveal the regulatory mechanism of iron homeostasis in rice under various iron concentrations and during iron supplementation. Both iron deficiency and excess hinder rice growth, with excess iron having a more severe effect especially on the roots. The reduction in nodal roots under excess iron conditions probably represents an adaptive mechanism to counteract iron toxicity. Iron stress and re-supplementation affect 4 652 differentially expressed genes. During iron supplementation in iron-deficient rice, there are upregulations at 10 min and 2 h, respectively, and a brief downregulation at 30 min of iron ion concentration and iron homeostasis related genes expression, indicating a protective mechanism in the roots during iron uptake. Notably, shoots that lack iron accumulation do not exhibit re-entry of iron after supplementation showing a sustained downregulation of iron-regulated genes. This suggests that the signaling from roots to shoots affects the response of shoots to iron supplementation in rice. The molecular changes of iron homeostasis discovered in this study can contribute to the rice improvement.