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

Abstract

Investigating the biological processes of iron (Fe) homeostasis is crucial for comprehending crop genetic improvement, which in turn helps address human malnutrition. This study utilized phenotyping, ionomics, and transcriptome analysis to uncover the regulatory mechanism of Fe homeostasis in rice under different Fe concentrations and during Fe supplementation. Our results showed both Fe deficiency and excess impede rice growth, with Fe excess exerting a more severe impact, particularly on the roots. The decrease in crown roots under excessive Fe conditions likely serves as an adaptive mechanism to counteract Fe toxicity. Transcriptomic analysis identified 4652 differentially expressed genes affected by Fe stress and supplementation. When Fe is supplemented to Fe-deficient rice, there are upregulations in the expression of genes related to Fe ion concentration and Fe homeostasis at 10 min and 2 h after supplementation, respectively, along with a brief downregulation at 30 min. This indicated a protective mechanism in the roots during Fe uptake. Notably, shoots with a lack of Fe accumulation did not show re-entry of Fe after supplementation, and there was a sustained downregulation of Fe-regulated genes. This suggests that the signaling from roots to shoots influences the response of shoots to Fe supplementation in rice. The molecular changes in Fe homeostasis discovered in this study can contribute to the improvement of rice.