Biology subjects

Guerinot, M. L.

Publications and source records attributed to Guerinot, M. L..

3 recordsLinked to original sources

bioRxiv2026

Iron-Flavonoid-Peroxidase Signaling Triggers Seed-Coat Remodeling for Rapid Germination

Seed germination and survival depend on a sustained water supply. We previously observed that iron (Fe) supply accelerates germination in tomato. Using Arabidopsis thaliana, we show here that increased Fe in the spermosphere acts as an extrinsic signal that increases seed coat permeability. Fe triggers structural remodeling of the cuticle covering the endosperm, as evidenced by loss of Auramine O staining in the testa-ruptured seeds. Fe-triggered germination phenotypes are compromised in the flavonoid (tt4 and tt7) and prx17 mutants, and in peroxidase inhibitor-treated wild-type seeds. We hypothesize that PRX17-driven peroxidase activity is governed by a maternal repressor-derepressor mechanism in which seed coat flavonoids constitutively repress enzyme activity. This repression is relieved by chelation of Fe by flavonoids, allowing PRX17 to remodel the cuticle and accelerate germination. To test this model, we examined the interaction between Fe and peroxidases with quercetin, a major seed coat flavonoid. Upon imbibition, quercetin is deglycosylated and inhibits PRX17 activity. Formation of Fe-quercetin complexes at the chalaza reduces the level of active quercetin, thereby restoring PRX17 activity in a dose-dependent manner. This study suggests that elevated Fe levels in oxygen-deprived, submerged soils prime seeds for rapid germination, a novel control mechanism mediated by seed coat biochemistry.

plant biology↗

bioRxiv2021

Natural variation in Arabidopsis ISR1 affects iron localization and induced systemic resistance

Beneficial root-associated bacteria can induce systemic resistance (ISR) to foliar pathogens and there is known transcriptional and genetic overlap in the root response to iron deficiency and ISR. A previous study found that there is natural variation in ISR among Arabidopsis accessions. The Ws accession is deficient in ISR, and the responsible recessive genetic locus, named ISR1, was mapped to chromosome 3. To find candidate genes that may underlie ISR deficiency in Ws, we identified genes that are induced in response to the ISR-triggering bacterium Pseudomonas simiae WCS417 and to iron stress and that have non-synonymous mutations in the Ws genome with respect to the ISR-responsive Col-0. We identified a kelch-domain containing protein encoded by At3g07720 that has a genomic rearrangement in Ws. We found that overexpression of Col-0 At3g07720 restores ISR to Ws, indicating that At3g07720 encodes ISR1. Isr1 loss of function mutants do not affect plant growth under iron limiting conditions but have increased levels of apoplastic iron. We found that iron supplementation, P. simiae WCS417, or a loss of isr1 enhance ROS production in a non-additive manner, suggesting they work through the same mechanism to enhance resistance. Our findings show that ISR1 is required for iron localization, immunity, and ISR, and suggest that increased iron uptake induced by ISR-eliciting bacteria may directly contribute to immunity through increased reactive oxygen production.

plant biology↗

bioRxiv2020

Arabidopsis thaliana zinc accumulation in leaf trichomes is correlated with zinc concentration in leaves

Zinc (Zn) is a key micronutrient. In humans, Zn deficiency is a common nutritional disorder, and most people acquire dietary Zn from eating plants. In plants, Zn deficiency can decrease plant growth and yield. Understanding Zn homeostasis in plants can improve agriculture and human health. While root Zn transporters in plat model species have been characterized in detail, comparatively little is known about shoot processes controlling Zn concentrations and spatial distribution. Previous work showed that Zn hyperaccumulator species such as Arabidopsis halleri accumulate Zn and other metals in leaf trichomes. The model species Arabidopsis thaliana is a non-accumulating plant, and to date there is no systematic study regarding Zn accumulation in A. thaliana trichomes. Here, we used Synchrotron X-Ray Fluorescence mapping to show that Zn accumulates at the base of trichomes of A. thaliana, as had seen previously for hyperaccumulators. Using transgenic and natural accessions of A. thaliana that vary in bulk leaf Zn concentration, we demonstrated that higher leaf Zn increases total Zn found at the base of trichome cells. Furthermore, our data suggests that Zn accumulates in the trichome apoplast, likely associated with the cell wall. Our data indicates that Zn accumulation in trichomes is a function of the Zn status of the plant, and provides the basis for future studies on a genetically tractable plant species aiming at understanding the molecular steps involved in Zn spatial distribution in leaves.

plant biology↗