Induced Systemic Resistance (ISR) and Fe Deficiency Responses in Dicot Plants

Abstract

Plants develop responses to abiotic stresses, like Fe deficiency. Similarly, plants also develop responses to cope with biotic stresses provoked by biological agents, like pathogens and insects. Some of these responses are limited to the infested damaged organ, but other responses systemically spread far from the infested organ and affect the whole plant. These latter responses include the Systemic Acquired Resistance (SAR) and the Induced Systemic Resistance (ISR). SAR is induced by pathogens and insects while ISR is mediated by beneficial microbes living in the rhizosphere, like bacteria and fungi. These root-associated mutualistic microbes, besides impacting on plant nutrition and growth, can further boost plant defenses, rendering the entire plant more resistant to pathogens and pests. In the last years, it has been found that ISR-eliciting microbes can induce both physiological and morphological responses to Fe deficiency in dicot plants. These results suggest that the regulation of both ISR and Fe deficiency responses overlap, at least partially. Indeed, several hormones and signaling molecules, like ethylene (ET), auxin, and nitric oxide (NO), and the transcription factor MYB72, emerged as key regulators of both processes. This convergence between ISR and Fe deficiency responses opens the way to the use of ISR-eliciting microbes as Fe biofertilizers as well as biopesticides. This review summarizes the progress in the understanding of the molecular overlap in the regulation of ISR and Fe deficiency responses in dicot plants. Root-associated mutualistic microbes, rhizobacteria and rhizofungi species, known for their ability to induce morphological and/or physiological responses to Fe deficiency in dicot plant species are also reviewed herein.

Analyzing Ash Leaf-Colonizing Fungal Communities for Their Biological Control of Hymenoscyphus fraxineus

“…Only a few fungal groups primarily belonging to P. flavescens and S. strictum, showed a distinctly higher abundance in tolerant ashes. These specific groups are suggested to improve pathogen tolerance, which could be mediated by competition, by inducing a systemic resistance or just by altering the microbial community structure (Pieterse et al, 2014;Romera et al, 2019). Additionally, in vitro tests of antagonism against H. fraxineus indicated clear inhibitory effects of various yeasts and particularly of several fast growing filamentous fungi.…”

Potential of microbes in the biofortification of Zn and Fe in dietary food grains. A review

“…Functional Zn transporters Ivanov and Bauer (2017), Ramesh et al (2003), Zheng et al (2018) Hordeum vulgare Zn acquisition in strategy I plants (in strategy II plants, this has been less studied), through the induction of Fe deficiency responses (Romera et al 2019;Verbon et al 2017). The ISR and the Fe uptake signaling pathways interact in plant roots via the transcription factor MYB72, which controls the biosynthesis of Fe-mobilizing phenolics.…”

Bacillus velezensis CLA178-Induced Systemic Resistance of Rosa multiflora Against Crown Gall Disease

“…The mechanism of the onset of ISR triggered by PGPR is incompletely understood; however, several stimulators have been proposed, such as flagellin, lipopolysaccharides (LPS), volatile organic compounds (VOCs), and siderophores (Romera et al, 2019). In plants, jasmonic acid (JA)/ethylene (ET) signaling pathways are important for the activation of ISR by PGPRs (Glazebrook et al, 2003;Pieterse et al, 2014).…”

“…Most of the studies on ISR were performed in Arabidopsis or crops. However, the signaling pathways involved in ISR may differ between various plant species and microbes (Romera et al, 2019).…”