Iron sensing in plants

Abstract

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.

Chlamydomonas cells transition through distinct Fe nutrition stages within 48 h of transfer to Fe-free medium

“…The factors mediating the transcriptional responses are not known in Chlamydomonas or other algae. We note that orthologs of MYB10 , PHR1 , BTSL1/2 , and bHLH34 involved in expression of the nutritional Fe regulon in land plants (Palmer et al 2013; Briat et al 2015; Vélez-Bermúdez and Schmidt 2023) are found in green algae as well (Urzica et al 2012; Roth et al 2017; Davidi et al 2023) (Supplemental Dataset S8).…”

Regulatory and Sensing Iron-Sulfur Clusters: New Insights and Unanswered Questions

“…Currently, there are hints that Fe-S clusters may be involved in iron sensing pathways, but no definitive evidence has been found to date [196]. As mentioned above, IRP1 has dual function as an RNA binding, iron response protein, and alternatively, as a cytosolic aconitase.…”

The Role of Iron in Phytopathogenic Microbe–Plant Interactions: Insights into Virulence and Host Immune Response

“…Further, iron is distributed to the sink tissues and utilized in the formation of enzyme cofactors, etc., or stored in vacuoles or complexed with ferritins. The mechanisms and regulations of iron homeostasis in plants have been extensively reviewed in recent years [ 94 , 95 , 96 , 97 , 98 , 99 ]. Here, we focus the discussion on recent advances in the understanding of plant iron homeostasis in the context of microbial infections and plant host responses.…”