The Putative Peptide Gene FEP1 Regulates Iron Deficiency Response in Arabidopsis

Abstract

Iron is an essential element for all organisms, and plants have developed sophisticated systems to acquire iron and maintain iron homeostasis. We found that an Arabidopsis thaliana abscisic acid-hypersensitive mutant, aba hypersensitive germination2-1 (ahg2-1), that is known to be defective in mitochondrial mRNA regulation had increased expression of iron deficiency response genes. The ahg2-1 mutant had lower heme levels than the wild type. Transcriptome data further revealed that novel genes encoding short polypeptides were highly expressed in this mutant. The expression of one of these genes, which we named FE-UPTAKE-INDUCING PEPTIDE 1 (FEP1), was induced under iron-deficient conditions and was observed in the vascular tissues of the leaves and roots, as well as in leaf mesophyll cells. Notably, deletion or insertion mutations of FEP1 exhibited impaired iron accumulation in shoots but normal iron levels in roots. Artificially induced expression of FEP1 was sufficient to induce iron deficiency response genes, such as basic HELIX-LOOP-HELIX 38 (bHLH38), bHLH39, IRON-REGULATED TRANSPORTER1 (IRT1), and FERRIC REDUCTION OXIDASE2 (FRO2), and led to iron accumulation in planta. Further analysis confirmed that the encoded peptide, but not the FEP1 RNA, was responsible for this activity. Remarkably, the activation of bHLH39 by FEP1 was independent of FER-LIKE IRON DEFICIENCY INDUCED (FIT), a key transcription factor in the iron deficiency response. Taken together, our results indicate that FEP1 functions in iron homeostasis through a previously undescribed regulatory mechanism for iron acquisition in Arabidopsis.

Regulation of the Poly(A) Status of Mitochondrial mRNA by Poly(A)-Specific Ribonuclease Is Conserved among Land Plants

“…It might be possible that the AGS1-AHG2 system was required to adapt to the terrestrial environment when plants landed during the evolution. This idea is consistent with the fact that Atahg2-1 has environmental stress-related phenotypes (Nishimura et al, 2005;Nishimura et al, 2009;Hirayama et al, 2018). Further analysis on the plant specific mitochondrial regulation will offer us clues to understand the unique and elaborated system of plants to cope with environment stresses.…”

Iron acquisition strategies in land plants: not so different after all

“…A recently discovered novel family of peptides named IRONMAN (IMA) or FE‐UPTAKE‐INDUCING PEPTIDE (FEP) positively regulates subgroup 1b bHLH genes in Arabidopsis (Grillet et al ., ; Hirayama et al ., ). Overexpression of IMAs causes iron and manganese accumulation, a function which is dependent on a C‐terminal amino acid motif that is conserved among IMA peptides across species (Grillet et al ., ).…”

PRC2-Mediated H3K27me3 Contributes to Transcriptional Regulation of FIT-Dependent Iron Deficiency Response

“…Recently, an iron-regulated calcium dependent protein kinase, CBL-INTERACTING PROTEIN KINASE (CIPK) 11, was identified as a positive regulator of FIT (Gratz et al, 2019). Meanwhile, IRON MAN (IMA) peptides, also referred as FE-UPTAKE-INDUCING PEPTIDEs (FEPs), were reported as an upstream regulator of the iron uptake pathway (Grillet et al, 2018; Hirayama et al, 2018). Overexpression of the IMA motif was sufficient to trigger the iron deficiency response and lead to accumulation of iron (Grillet et al, 2018), but IMA3/FEP1 was proposed to activate bHLH38/39 via a mechanism independent of FIT, with the expression of FEP1 also being independent of FIT (Hirayama et al, 2018).…”