Abstract
Knowledge accumulated on the regulation of iron (Fe) homeostasis, its intracellular trafficking and transport across various cellular compartments and organs in plants; storage proteins, transporters and transcription factors involved in Fe metabolism have been analyzed in detail in recent years. However, the key sensor(s) of cellular plant “Fe status” triggering the long-distance shoot–root signaling and leading to the root Fe deficiency responses is (are) still unknown. Local Fe sensing is also a major task for roots, for adjusting the internal Fe requirements to external Fe availability: how such sensing is achieved and how it leads to metabolic adjustments in case of nutrient shortage, is mostly unknown. Two proteins belonging to the 2′-OG-dependent dioxygenases family accumulate several folds in Fe-deficient Arabidopsis roots. Such proteins require Fe(II) as enzymatic cofactor; one of their subgroups, the HIF-P4H (hypoxia-inducible factor-prolyl 4-hydroxylase), is an effective oxygen sensor in animal cells. We envisage here the possibility that some members of the 2′-OG dioxygenase family may be involved in the Fe deficiency response and in the metabolic adjustments to Fe deficiency or even in sensing Fe, in plant cells.
Highlights
Iron is an essential micronutrient for plants it is potentially toxic, when present in a free, non-complexed form
Knowledge accumulated on the regulation of iron (Fe) homeostasis, its intracellular trafficking and transport across various cellular compartments and organs in plants; storage proteins, transporters and transcription factors involved in Fe metabolism have been analyzed in detail in recent years
Two proteins belonging to the 2 -OG-dependent dioxygenases family accumulate several folds in Fe-deficient Arabidopsis roots
Summary
Iron is an essential micronutrient for plants it is potentially toxic, when present in a free, non-complexed form. In accordance with results obtained by iTRAQ (isobaric peptide tags for relative and absolute quantitation) analysis of Fe-deficient roots (Lan et al, 2011), both At3g12900 and At3g136100 show positive correlation with genes actively involved in the Fe deficiency response, such as iron-regulated transporter 1 (IRT1; Vert et al, 2002), ferric-chelate oxidase reductase (FRO2; Connolly et al, 2003) CYP82C4 (Murgia et al, 2011), ferroportin/ironregulated (IREG2; Morrissey et al, 2009) metal tolerance protein (MTP3; Arrivault et al, 2006)(Table 2); viceversa, they show no significant correlation with the ferritin genes since their correlation values fall within the [−0.3 + 0.02] range (data not shown). Regarding the genes in class 2, it is interesting to notice that beside with the Fe-related genes, the positive control At3g13610
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