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. 2020 Oct 2;15(10):1795582.
doi: 10.1080/15592324.2020.1795582. Epub 2020 Jul 21.

Further insights into the role of bHLH121 in the regulation of iron homeostasis in Arabidopsis thaliana

Fei Gao  1 , Kevin Robe  1 , Christian Dubos  1
Affiliations

Further insights into the role of bHLH121 in the regulation of iron homeostasis in Arabidopsis thaliana

Fei Gao et al. Plant Signal Behav. .

Abstract

Iron (Fe) is an important micronutrient for plant growth and development but any excess of Fe is toxic because of the Fe-dependent generation of reactive oxygen species (ROS). Thus, Fe homeostasis must be tightly regulated. In Arabidopsis thaliana, a cascade of transcription factors has been identified as involved in the regulation of this process by modulating the expression of genes related to Fe uptake, transport, and storage. Recently, it was demonstrated that in response to Fe deficiency, bHLH121/URI (UPSTREAM REGULATOR OF IRT1) directly activates the expression of several genes involved in this regulatory network. It was also shown that bHLH121 interacts with ILR3 (bHLH105) and its homologs. Herein it is shown that bHLH121 is necessary for the expression of the main markers of the plant responses to Fe excess, the ferritin genes (i.e. FER1, FER3, and FER4). bHLH121 regulates ferritin genes expression by directly binding to their promoters, at the same locus than the ILR3-PYE repressive complex. Therefore, this study highlight that bHLH121, PYE, and ILR3 form a chain of antagonistic switches that regulate the expression of ferritin genes. The implication of this finding is discussed.

Keywords: Arabidopsis thaliana; ILR3; PYE; bHLH105; bHLH121; bHLH47; basic helix-loop-helix; ferritins; iron homeostasis; transcription factor.

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Figures

Figure 1.
Figure 1.
Loss-of-function of bHLH121 leads to severe iron deficiency symptoms that can be rescued by extra iron supply.
Figure 2.
Figure 2.
bHLH121 is an activator of the Arabidopsis thaliana FER1, FER3 and FER4 expression.
Figure 3.
Figure 3.
bHLH121 is a direct activator of the Arabidopsis thaliana FER1, FER3 and FER4 expression.
See this image and copyright information in PMC

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