Fitting into the Harsh Reality: Regulation of Iron-deficiency Responses in Dicotyledonous Plants

Abstract

Iron is an essential element for life on Earth and its shortage, or excess, in the living organism may lead to severe health disorders. Plants serve as the primary source of dietary iron and improving crop iron content is an important step towards a better public health. Our review focuses on the control of iron acquisition in dicotyledonous plants and monocots that apply a reduction-based strategy in order to mobilize and import iron from the rhizosphere. Achieving a balance between shortage and excess of iron requires a tight regulation of the activity of the iron uptake system. A number of studies, ranging from single gene characterization to systems biology analyses, have led to the rapid expansion of our knowledge on iron uptake in recent years. Here, we summarize the novel insights into the regulation of iron acquisition and internal mobilization from intracellular stores. We present a detailed view of the main known regulatory networks defined by the Arabidopsis regulators FIT and POPEYE (PYE). Additionally, we analyze the root and leaf iron-responsive regulatory networks, revealing novel potential gene interactions and reliable iron-deficiency marker genes. We discuss perspectives and open questions with regard to iron sensing and post-translational regulation.

The bHLH Transcription Factor bHLH104 Interacts with IAA-LEUCINE RESISTANT3 and Modulates Iron Homeostasis in Arabidopsis

“…A number of transcription factors involved in Fe homeostasis have been identified. In Arabidopsis thaliana, two regulatory networks, the FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT) network and the POPEYE (PYE) network, were verified to modulate Fe deficiency responses (Ivanov et al, 2012). Both FIT and PYE are members of the basic helix-loop-helix (bHLH) transcription factor family, suggesting the importance of bHLH proteins in Fe homeostasis.…”

Increased de novo riboflavin synthesis and hydrolysis of FMN are involved in riboflavin secretion from Hyoscyamus albus hairy roots under iron deficiency

“…In particular, plants growing on calcareous soils are at risk of Fe deficiency because although ferric ions are often abundant in these soils they are largely unavailable to plant roots, owing to the extremely low solubility of ferric compounds. Therefore, mechanisms for the avoidance or correction of Fe deficiency in plants have been intensively studied [6][7][8][9][10]. However, it is not yet known why or how some plant species secrete flavins from their roots under conditions of Fe deficiency.…”

Investigation of copper homeostasis in plant cells by fluorescence lifetime imaging microscopy

“…Cu is mainly imported in a reduced state (Cu + ) by the Ctr-family transporters COPT1 and potentially COPT2, however Zipfamily bivalent metal transporters might also be implicated in Cu import, thus Cu uptake uses common elements and shows potential co-regulation with the iron uptake system. [4][5][6][7] Once Cu is internalized, multiple proteins are suggested to be involved in its allocation in the form of both Cu + and Cu 2+ between the cytoplasm and the vacuole, plastids, mitochondria or the endoplasmic reticulum. 1,8 This compartmentalization is important, as apart from detoxification, Cu is required as a cofactor for plastocyanin during photosynthesis, the function of the respiratory chain in the mitochondria etc.…”