The effector FEP3/IRON MAN1 modulates interaction between BRUTUS-LIKE1 and bHLH subgroup IVb and IVc proteins

Iron (Fe) is an essential micronutrient for plant growth and development, participating in many significant biological processes including photosynthesis, respiration, and nitrogen fixation. Although abundant in the earth’s crust, most Fe is oxidized and difficult for plants to absorb under aerobic and alkaline pH conditions. Plants, therefore, have evolved complex means to optimize their Fe-acquisition efficiency. In the past two decades, regulatory networks of transcription factors and ubiquitin ligases have proven to be essential for plant Fe uptake and translocation. Recent studies in Arabidopsis thaliana (Arabidopsis) suggest that in addition to the transcriptional network, IRON MAN/FE-UPTAKE-INDUCING PEPTIDE (IMA/FEP) peptide interacts with a ubiquitin ligase, BRUTUS (BTS)/BTS-LIKE (BTSL). Under Fe-deficient conditions, IMA/FEP peptides compete with IVc subgroup bHLH transcription factors (TFs) to interact with BTS/BTSL. The resulting complex inhibits the degradation of these TFs by BTS/BTSL, which is important for maintaining the Fe-deficiency response in roots. Furthermore, IMA/FEP peptides control systemic Fe signaling. By organ-to-organ communication in Arabidopsis, Fe deficiency in one part of a root drives the upregulation of a high-affinity Fe-uptake system in other root regions surrounded by sufficient levels of Fe. IMA/FEP peptides regulate this compensatory response through Fe-deficiency-triggered organ-to-organ communication. This mini-review summarizes recent advances in understanding how IMA/FEP peptides function in the intracellular signaling of the Fe-deficiency response and systemic Fe signaling to regulate Fe acquisition.

Section: Introductionmentioning

confidence: 99%

Regulation of the iron-deficiency response by IMA/FEP peptide

Tabata

2023

“…It was recently shown that IRON MAN (IMA) peptides interact with and are ubiquitinated by BTS, which inhibits the degradation of bHLH105 and bHLH115 through binding competition (Li et al, 2021). In the same line of evidence, the interaction of BTSL1 with PYE and bHLHs of the subgroup IVc is attenuated by the peptide IMA1 (Lichtblau et al, 2022). Interestingly, mutation applied to the Model for transcriptional regulation of Fe homeostasis.…”

Section: Transcriptional Regulationmentioning

confidence: 99%

Multilayered regulation of iron homeostasis in Arabidopsis

Spielmann,

Fanara,

Cotelle

et al. 2023

Iron (Fe) is an essential micronutrient for plant growth and development due to its role in crucial processes such as photosynthesis and modulation of the redox state as an electron donor. While Fe is one of the five most abundant metals in the Earth’s crust, it is poorly accessible to plants in alkaline soils due to the formation of insoluble complexes. To limit Fe deficiency symptoms, plant have developed a highly sophisticated regulation network including Fe sensing, transcriptional regulation of Fe-deficiency responsive genes, and post-translational modifications of Fe transporters. In this mini-review, we detail how plants perceive intracellular Fe status and how they regulate transporters involved in Fe uptake through a complex cascade of transcription factors. We also describe the current knowledge about intracellular trafficking, including secretion to the plasma membrane, endocytosis, recycling, and degradation of the two main Fe transporters, IRON-REGULATED TRANSPORTER 1 (IRT1) and NATURAL RESISTANCE ASSOCIATED MACROPHAGE PROTEIN 1 (NRAMP1). Regulation of these transporters by their non-Fe substrates is discussed in relation to their functional role to avoid accumulation of these toxic metals during Fe limitation.

“…Owing to their increased abundance upon Fe deficiency, IMA peptides compete with clade IVc bHLH proteins for binding to BTS, preventing their degradation and promote induction of downstream Fe deficiency responses (Figure 2) (Li et al, 2021). Interaction with IMA peptides, specifically IMA1/FEP3, has also been demonstrated for BTSL proteins (Lichtblau et al, 2022) OsIMA1 and OsIMA2 appear to function similar to Arabidopsis IMA/FEP peptides (Kobayashi et al, 2021). Overexpression of both homologs conferred Fe deficiency tolerance to rice plants and led to the accumulation of Fe in all tissues, including seeds.…”

Section: Ironman and Other Superheroes: Fe Sensing In Plantsmentioning

confidence: 99%

Iron sensing in plants

Vélez‐Bermúdez

Schmidt²

2023

The ease of accepting or donating electrons is the raison d’être for the pivotal role iron (Fe) plays in a multitude of vital processes. In the presence of oxygen, however, this very property promotes the formation of immobile Fe(III) oxyhydroxides in the soil, which limits the concentration of Fe that is available for uptake by plant roots to levels well below the plant’s demand. To adequately respond to a shortage (or, in the absence of oxygen, a possible surplus) in Fe supply, plants have to perceive and decode information on both external Fe levels and the internal Fe status. As a further challenge, such cues have to be translated into appropriate responses to satisfy (but not overload) the demand of sink (i.e., non-root) tissues. While this seems to be a straightforward task for evolution, the multitude of possible inputs into the Fe signaling circuitry suggests diversified sensing mechanisms that concertedly contribute to govern whole plant and cellular Fe homeostasis. Here, we review recent progress in elucidating early events in Fe sensing and signaling that steer downstream adaptive responses. The emerging picture suggests that Fe sensing is not a central event but occurs in distinct locations linked to distinct biotic and abiotic signaling networks that together tune Fe levels, Fe uptake, root growth, and immunity in an interwoven manner to orchestrate and prioritize multiple physiological readouts.