Iron counteracts zinc-induced toxicity in soybeans

Authors: OLIVEIRA, NATALIA - Cornell University; NAMORATO, FILIPE - Cornell University; RAO, SOMBIR - Cornell University; CARDOSO, ARNON - Cornell University; RENENDELUIZ, PEDRO - Federal University Of Lavras; GUIHERME, LUIZ - Federal University Of Lavras; Liu, Jiping; Li, Li

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2022
Publication Date: 1/15/2023
Citation: Oliveira, N., Namorato, F., Rao, S., Cardoso, A., Renendeluiz, P., Guiherme, L., Liu, J., Li, L. 2023. Iron counteracts zinc-induced toxicity in soybeans. Plant Physiology and Biochemistry. 194:335-344. https://doi.org/10.1016/j.plaphy.2022.11.024.
DOI: https://doi.org/10.1016/j.plaphy.2022.11.024

Interpretive Summary: Zinc and iron are essential micronutrients for all living organisms and the major targets for crop biofortification. Their interactions greatly affect their uptake and homeostasis in plants. In this study, we examined the interaction between Zn and Fe in soybean plants. We found that Zn levels are greatly affected by Fe supplies, but not in reverse. High Zn induces typical Fe deficiency symptoms under low Fe conditions, which can be counteracted by increased levels of Fe supplies. Such a phenomenon is not directly associated with low Fe content but with the deleterious effects of excess Zn. Noticeably, the combination of high Zn and low Fe treatment greatly activates the expression of two primary components of Fe uptake and regulation in soybean roots. These findings advance our understanding of Zn and Fe interaction and the heavy metals-induced Fe deficiency-like symptom.

Technical Abstract: Zinc (Zn) and iron (Fe) are essential micronutrients for all living organisms and the major targets for crop biofortification. However, when acquired in excess quantities, Zn and Fe can be toxic to plants. In this study, we examined the interaction between Zn and Fe in soybean plants under various Zn and Fe treatments. While the level of Zn accumulation increased with increasing Zn supplies, Zn content greatly decreased with rising Fe supplies. Moreover, Zn uptake rates were negatively correlated with Fe supplies. However, Fe accumulation was not greatly affected by elevating Zn supplies. Excess Zn supplies were found to induce typical Fe deficiency symptoms under low Fe conditions, which can be counteracted by increasing Fe supplies. Interestingly, leaf chlorosis caused by excess Zn and low Fe supplies was not directly associated with reduced total Fe content but likely associated with deleterious effects of excess Zn. The combination of high Zn and low Fe greatly activates FRO2 and FIT1 gene expression in soybean roots. Besides, Zn-Fe interaction influences the activities of antioxidative enzymes as well as the uptake, accumulation, and homeostasis of other essential micronutrients, such as copper and manganese in soybean plants. These findings provide new perspectives on Zn and Fe interaction and on heavy metal-induced Fe deficiency-like symptoms.