Is There a Role for Glutaredoxins and BOLAs in the Perception of the Cellular Iron Status in Plants?

Pascal Rey,Florence Vignols,Maël Taupin-Broggini,Jérémy Couturier,Nicolas Rouhier

doi:10.3389/fpls.2019.00712

Abstract

Glutaredoxins (GRXs) have at least three major identified functions. In apoforms, they exhibit oxidoreductase activity controlling notably protein glutathionylation/deglutathionylation. In holoforms, i.e., iron–sulfur (Fe–S) cluster-bridging forms, they act as maturation factors for the biogenesis of Fe–S proteins or as regulators of iron homeostasis contributing directly or indirectly to the sensing of cellular iron status and/or distribution. The latter functions seem intimately connected with the capacity of specific GRXs to form [2Fe–2S] cluster-bridging homodimeric or heterodimeric complexes with BOLA proteins. In yeast species, both proteins modulate the localization and/or activity of transcription factors regulating genes coding for proteins involved in iron uptake and intracellular sequestration in response notably to iron deficiency. Whereas vertebrate GRX and BOLA isoforms may display similar functions, the involved partner proteins are different. We perform here a critical evaluation of the results supporting the implication of both protein families in similar signaling pathways in plants and provide ideas and experimental strategies to delineate further their functions.

Highlights

Many cellular reactions and biological processes require metalloproteins, among which those containing iron (Fe) cofactors such as mononuclear and dinuclear Fe centers, hemes and iron–sulfur (Fe–S) clusters, are crucial
Cytosolic and nuclear Fe–S proteins are maturated via the eukaryote-specific cytosolic iron– sulfur cluster assembly (CIA) machinery, which is, dependent on the mitochondrial ISC machinery for sulfur supply (Lill, 2009)
The Fe sensing systems and associated transcription factors generally differ in bacteria, yeast/fungi, mammals, and plants, but might include common actors such as glutaredoxins (GRXs) and BOLAs (Couturier et al, 2015)

Summary

Introduction

Many cellular reactions and biological processes require metalloproteins, among which those containing iron (Fe) cofactors such as mononuclear and dinuclear (non-heme) Fe centers, hemes and iron–sulfur (Fe–S) clusters, are crucial. Pioneer works revealed functions for Escherichia coli BolA in the regulation of cell morphology, possibly as a transcriptional regulator (Aldea et al, 1989), for Saccharomyces cerevisiae cytosolic Bol2/Fra2 (Fe repressor of activation 2) in the regulation of iron homeostasis (Lesuisse et al, 2005; Kumánovics et al, 2008), and for mitochondrial BOLAs (human BOLA3 and yeast Bol1, Bol3) in the maturation of Fe–S clusters (Table 1; Cameron et al, 2011; Melber et al, 2016; Uzarska et al, 2016).

Results

Conclusion