Iron (Fe) is an essential micronutrient for plant growth and development since it is required for the activity of several enzymes involved in fundamental processes such as photosynthesis and respiration. The availability of this micronutrient for plants depends on the nature of the soil and the plant’s ability to take it up. In order to avoid any deficiency or excess that could be detrimental, plants have evolved sophisticated molecular mechanisms to maintain Fe homeostasis.

A cascade of transcription factors (TFs) controls this process by regulating the expression of genes involved in Fe uptake, transport, and storage. Understanding how this regulatory cascade is regulated might help improve food crop production without the use of Fe fertilizers, as these fertilizers are expensive and their sustainability in modern agriculture is questionable.

In the frame of this study, using Arabidopsis thaliana as model plant species, we have shown that bHLH121 acts upstream of the Fe homeostasis regulatory network. Within this network, bHLH121 directly regulates the expression of genes encoding most TFs and associated regulatory proteins/peptides involved in this process. Interestingly, Fe availability does not modulate bHLH121 expression but instead affects its protein localization within the root tissues. Taken together, these results place bHLH121 as a major player in the control of Fe homeostasis in plants.

Gao F, Robe K, Bettembourg M, Navarro N, Rofidal V, Santoni V, Gaymard F, Vignols F, Roschzttardtz H, Izquierdo E, Dubos C✉ (2020) The transcription factor bHLH121 interacts with bHLH105 (ILR3) and its closest homologs to regulate iron homeostasis in Arabidopsis. Plant Cell, 32(2):508-524