Iron (Fe) is essential for plant growth, playing critical roles in photosynthesis, respiration, and metabolism. However, iron availability in soil is highly variable.Too little iron starves the plant, and too much becomes toxic. It becomes essential to understand how plants strike the right balance?

In a study published in The Plant Cell, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences have identified a protein named CITF1 (COPPER DEFICIENCY INDUCED TRANSCRIPTION FACTOR 1) that serves as a negative regulator of iron uptake in Arabidopsis thaliana. CITF1 achieves this by directly interacting with FIT (FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR), a master transcription factor that activates iron-absorption genes.

To unravel this regulatory mechanism, the researchers employed a multi-faceted approach, combining phenotypic analysis, genetic validation, protein interaction assays, subcellular localization studies, and biochemical functional analyses.

Their experiments showed that under low-iron conditions, citf1 mutant plants developed longer roots, enhanced rhizosphere acidification, and increased iron reductase activity. Conversely, plants overexpressing CITF1 showed reduced iron absorption. Crucially, when the FIT gene was deleted, manipulating CITF1 had no effect on iron nutrition, proving that CITF1's regulation of iron uptake is entirely dependent on FIT.

Further investigation showed that CITF1 does not simply turn FIT on or off; instead, it fine-tunes FIT activity through three distinct pathways: interfering with the interaction between BTSL1/2 and FIT, relocating FIT protein from the nucleus to the cytoplasm, and forming a FIT–CITF1 dimer that suppresses FIT-mediated activation of iron-uptake genes. These layered controls allow plants to dynamically adjust their iron absorption in response to fluctuating environmental iron levels.

The findings carry significant practical implications. Iron deficiency is a leading cause of crop yield losses and a major contributor to human malnutrition, particularly iron-deficiency anemia. By manipulating regulators such as CITF1, it may become possible in the future to engineer crops that absorb optimal amounts of iron, even under challenging soil conditions.

“Our work reveals a novel post-translational regulatory layer in iron homeostasis. CITF1 acts as a molecular rheostat, not an on-off switch, allowing plants to adapt iron uptake to environmental cues,” said LIANG Gang of XTBG.

Published: 13 June 2026