Copper (Cu) plays a pivotal role in sustaining plant growth, development, and overall food yield and quality. To achieve this delicate balance, plants must meticulously regulate the uptake and transport of copper throughout various tissues and organs, thereby maintaining copper homeostasis. A recent study conducted by researchers at the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences, published in New Phytologist, sheds light on the involvement of Iron Man peptides (IMAs) in this essential process.
While IMAs have previously been identified for their role in mediating iron (Fe) homeostasis in Arabidopsis thaliana, their potential involvement in copper homeostasis remained uncertain. The XTBG researchers conducted comprehensive investigations to explore the relationship between IMAs and copper-deficiency responses.
The study commenced by examining whether the expression of IMA genes responds to changes in copper concentration. The researchers observed that Cu deficiency repressed the transcription of IMA genes. Intriguingly, disrupting all IMA genes simultaneously increased tolerance to copper deficiency, leading to elevated transcript abundance of copper uptake genes. Conversely, overexpressing IMA1 or IMA3 had the opposite effect.
Protein interaction assays were then employed to delve into the molecular mechanisms at play. The researchers discovered that IMAs interact with Cu-DEFICIENCY INDUCED TRANSCRIPTION FACTOR1 (CITF1), a positive regulator of copper uptake genes. This interaction not only interfered with the DNA binding capability of CITF1 but also repressed its transcriptional activation activity. In essence, IMAs downregulated the expression of copper uptake genes.
Moreover, the study revealed that when copper is sufficient, IMAs prevent CITF1 from binding to the promoters of copper uptake genes, inhibiting its activation of these genes. Conversely, under copper-deficient conditions, the expression of IMAs is repressed, allowing CITF1 to play its role in activating copper uptake genes.
Liang Gang of XTBG highlighted the significance of the findings, stating, “This study suggests that IMAs are a new component of the copper deficiency response signaling pathway. It provides experimental support for the existence of a sophisticated system that allows plants to dynamically respond to copper status.”
This research not only advances our understanding of the intricate mechanisms governing copper homeostasis in plants but also underscores the importance of IMAs in orchestrating these vital processes.