Iron and Immunity

Abstract

Iron is an essential nutrient for most life on Earth because it functions as a crucial redox catalyst in many cellular processes. However, when present in excess iron can lead to the formation of harmful hydroxyl radicals. Hence, the cellular iron balance must be tightly controlled. Perturbation of iron homeostasis is a major strategy in host-pathogen interactions. Plants use iron-withholding strategies to reduce pathogen virulence or to locally increase iron levels to activate a toxic oxidative burst. Some plant pathogens counteract such defenses by secreting iron-scavenging siderophores that promote iron uptake and alleviate iron-regulated host immune responses. Mutualistic root microbiota can also influence plant disease via iron. They compete for iron with soil-borne pathogens or induce a systemic resistance that shares early signaling components with the root iron-uptake machinery. This review describes the progress in our understanding of the role of iron homeostasis in both pathogenic and beneficial plant-microbe interactions.

Effect of long‐term organic and mineral fertilization strategies on rhizosphere microbiota assemblage and performance of lettuce

“…Our observations are further supported by the upregulation of the OPT3 gene, a key component of Fe signalling network (Zhai et al, 2014;Khan et al, 2018) indicating deficiency in bio-available Fe. It has been recently proposed that rhizosphere microbes can induce MYB72/BGLU42-dependent ISR response via iron-mobilizing phenolics, simulating root iron-deficiency response and changes in iron-homeostasis mechanisms in the rhizosphere, which can be expressed systemically throughout the plant (Verbon et al, 2017;Stringlis et al, 2018). In addition, it is assumed that the plant immunity has co-evolved with the plant microbiome and thus plays an essential role in determining the structure of the plant-associated microbiota (Turner et al, 2013).…”

Airborne signals from Trichoderma fungi stimulate iron uptake responses in roots resulting in priming of jasmonic acid‐dependent defences in shoots of Arabidopsis thaliana and Solanum lycopersicum

“…; Zamioudis et al . ; Verbon et al ). The core of this Fe uptake response includes acidification of the rhizosphere via proton extrusion by H + ‐ATPases (Santi & Schmid ), reduction of ferric Fe (Fe 3+ ) to ferrous Fe (Fe 2+ ) via the plasma membrane protein FRO2 (FERRIC REDUCTION OXIDASE2; Robinson et al .…”

“…Besides its key role in the onset of microbe-induced ISR, MYB72 has been demonstrated to play a critical role in the survival of Arabidopsis plants in soils where iron (Fe) availability is restricted (Palmer et al 2013). In response to Fe starvation, MYB72 is rapidly up-regulated in Arabidopsis roots as part of a set of coordinated responses, collectively referred to as the Strategy I Fe deficiency response, which boosts Fe mobilization and uptake from the soil Buckhout et al 2009;Zamioudis et al 2014;Zamioudis et al 2015;Verbon et al 2017). The core of this Fe uptake response includes acidification of the rhizosphere via proton extrusion by H + -ATPases (Santi & Schmid 2009), reduction of ferric Fe (Fe 3+ ) to ferrous Fe (Fe 2+ ) via the plasma membrane protein FRO2 (FERRIC REDUCTION OXIDASE2; Robinson et al 1999) and the subsequent transport of ferrous Fe from the soil into root cells via the high-affinity ferrous Fe transporter IRT1 (FE-REGULATED TRANSPORTER1; Eide et al 1996).…”

The arbuscular mycorrhizal fungus Rhizophagus irregularis uses a reductive iron assimilation pathway for high‐affinity iron uptake

“…In the mammalian and plant innate immune system, Fe-withholding strategies play a central role in preventing invading pathogens entering the hosts (Lemanceau et al, 2009;Cassat and Skaar, 2013). Interestingly, Fe immunity is also involved in beneficial plant-microbe interactions (Verbon et al, 2017).…”