Biology subjects

Reichheld, J.-P.

Publications and source records attributed to Reichheld, J.-P..

7 recordsLinked to original sources

bioRxiv2026

Cytosolic GLUCOSE-6-PHOSPHATE DEHYDROGENASE 5 is a key player in redox homeostasis during oxidative stress and in oxidative stress-triggered activation of the salicylic acid pathway

Glucose-6-phosphate dehydrogenase (G6PDH) catalyzes the first step of the oxidative pentose phosphate pathway, generating NADPH to sustain redox metabolism and signaling. However, whether individual G6PDH isoforms directly regulate oxidative stress signaling remains unclear. To determine the contribution of the different Arabidopsis G6PDH isoforms to oxidative stress signaling, we introduced single T-DNA mutants into the catalase-deficient cat2 background, a genetic system in which intracellular H2O2 production activates salicylic acid (SA)-dependent cell death and defense pathways. Interestingly, impairment of cytosolic, but not chloroplastic G6PDH activity suppressed cat2-triggered phenotypes, with loss of G6PD5 function fully abolishing lesion formation. The cat2 g6pd5 double mutant phenocopied the SA biosynthesis-deficient mutant cat2 sid2 and showed reversion of defense responses as well as metabolomic and transcriptomic profiles to the wild-type state. Strikingly, despite the suppression of SA-dependent lesions, loss of G6PD5 activity does not appear to reduce stress intensity. On the contrary, cat2 g6pd5 plants exhibit increased glutathione synthesis and oxidation, elevated expression of oxidative stress marker genes, and enhanced accumulation of reactive nitrogen species relative to cat2. Protein-protein interaction analyses revealed that G6PD5 associates with several redox and defense-related proteins. In particular, we confirmed a physical interaction between G6PD5 and thioredoxin h5, a key component of redox-dependent SA signaling. However, analysis of cat2 trxh5 and cat2 npr1 lines indicated that this interaction alone cannot explain the G6PD5-dependent control of SA responses. Our work reveals that cytosolic G6PD5 integrates redox metabolism with immune signaling to control plant responses to oxidative stress.

plant biology↗

bioRxiv2025

Root growth in Arabidopsis depends on the amount of glutathione and not the glutathione redox potential

Cell cycle activity and hence plant growth strictly depends on glutathione homeostasis. Despite compelling evidence for this dependency based on glutathione depletion, the cause for the cell cycle arrest had remained unclear. Cell cycle control may depend on either the absolute amount of glutathione or on the glutathione redox potential (EGSH). To unambiguously distinguish those two options, we characterized an allelic series of six Arabidopsis mutants affected in glutamate-cysteine ligase, which catalyses the first step for the biosynthesis of reduced glutathione (GSH). When grown under the same conditions, even mutants with 20% and 50% of wild-type GSH amounts are slightly stunted. The most severely compromised mutants, zir1 and rml1, were crossed with either gr1, which lacks cyto-nuclear glutathione disulfide reductase and was used to induce a pronounced shift in EGSH, or with bir6, which has a diminished glutathione consumption and thus exhibits slightly increased levels of GSH. Based on theoretical considerations, these levels are not expected to shift the EGSH to any significant extent. Our study shows that deleting GR1 in the zir1 or rml1 background does not result in an obvious phenotypic change. By contrast, deleting BIR6 was sufficient to suppress the growth arrest in rml1 and to attenuate the growth in zir1. These findings demonstrate that root growth is dependent on the availability of sufficient amounts of GSH, and not affected by pronounced changes in EGSH. This insight provides a decisive step towards understanding the mechanisms underpinning the proposed role of glutathione in cell cycle and growth control. HighlightCrosses of GSH-deficient Arabidopsis mutants with mutants affected in glutathione reduction or GSH consumption pinpoint the GSH amount rather than the glutathione redox potential as causative for changes in root growth.

plant biology↗

bioRxiv2023

Glutaredoxin regulation of primary root growth confers early drought stress tolerance in pearl millet

Seedling root traits impact plant establishment under challenging environments. Pearl millet is one of the most heat and drought tolerant cereal crops that provides a vital food source across the sub-Saharan Sahel region. Pearl millets early root system features a single fast-growing primary root which we hypothesize is an adaptation to the Sahelian climate. Using crop modelling, we demonstrate that early drought stress is an important constraint in agrosystems in the Sahel where pearl millet was domesticated. Furthermore, we show that increased pearl millet primary root growth is correlated with increased early water stress tolerance in field conditions. Genetics including GWAS and QTL approaches identify genomic regions controlling this key root trait. Combining gene expression data, re-sequencing and re-annotation of one of these genomic regions identified a glutaredoxin-encoding gene PgGRXC9 as the candidate stress resilience root growth regulator. Functional characterization of its closest Arabidopsis homolog AtROXY19 revealed a novel role for this glutaredoxin (GRX) gene clade in regulating cell elongation. In summary, our study suggests a conserved function for GRX genes in conferring root cell elongation and enhancing resilience of pearl millet to its Sahelian environment.

plant biology↗

bioRxiv2022

Glutathione-mediated plant response to high-temperature

Climate change induce global warming and intense heat waves that affect plant development and productivity. Among the molecular perturbations that high temperature induces in living cells is the accumulation of reactive oxygen species (ROS), which can damage macromolecules of the cell and perturb the cellular redox state. To cope with deleterious effects of ROS, plant, as other organisms, have developed strategies to scavenge ROS and to regulate their redox state. Among those, glutathione plays a major role in maintaining the cellular redox state and the function of key antioxidant enzymes like peroxidases. Here, we investigated the contribution of the redox systems in plant adaptation to high temperature. We studied two different high temperature regimes: a rise of ambient temperature to 27{degrees}C inducing a plant developmental adaptation program called thermomorphogenesis, and a 37{degrees}C treatment mimicking intense heat wave and affecting plant viability. Using the genetically encoded redox marker roGFP, we show that high temperature regimes lead to cytoplasm and nuclear oxidation and impact profoundly the glutathione pool rather than the glutathione redox state. Moreover, plant can restore the pool within a few hours, which likely contribute to plant adaptation to high temperature. However, conditional glutathione deficient mutants fail to adapt to intense heat waves or to induce thermomorphogenesis, suggesting that glutathione is involved in both heat adaptation mechanisms. We also evaluate by RNAseq analyses, how plant change its genome expression signature upon heat stress and identified a marked genome expression deviation in mutant deficient in glutathione antioxidant which might contribute to its sensitivity to high temperature. Thus, we define glutathione as a major antioxidant molecule acting in the adaptation of plant to rise of temperature.

plant biology↗

bioRxiv2020

Redox response of iron-sulfur glutaredoxin GRXS17 activates its holdase activity to protect plants from heat stress

Living organisms use a large panel of mechanisms to protect themselves from environmental stress. Particularly, heat stress induces misfolding and aggregation of proteins which are guarded by chaperone systems. Here, we examine the function the glutaredoxin GRXS17, a member of thiol reductases families in the model plant Arabidopsis thaliana. GRXS17 is a nucleocytosolic monothiol glutaredoxin consisting of an N-terminal thioredoxin (TRX)-domain and three CGFS-active site motif-containing GRX-domains that coordinate three iron-sulfur (Fe-S) clusters in a glutathione (GSH)-dependent manner. As a Fe-S cluster-charged holoenzyme, GRXS17 is likely involved in the maturation of cytosolic and nuclear Fe-S proteins. In addition to its role in cluster biogenesis, we showed that GRXS17 presents both foldase and redox-dependent holdase activities. Oxidative stress in combination with heat stress induces loss of its Fe-S clusters followed by subsequent formation of disulfide bonds between conserved active site cysteines in the corresponding TRX domains. This oxidation leads to a shift of GRXS17 to a high-MW complex and thus, activates its holdase activity. Moreover, we demonstrate that GRXS17 is specifically involved in plant tolerance to moderate high temperature and protects root meristematic cells from heat-induced cell death. Finally, we showed that upon heat stress, GRXS17 changes its client proteins, possibly to protect them from heat injuries. Therefore, we propose that the iron-sulfur cluster enzyme glutaredoxin GRXS17 is an essential guard to protect proteins against moderate heat stress, likely through a redox-dependent chaperone activity. All in all, we reveal the mechanism of an Fe-S cluster-dependent activity shift, turning the holoenzyme GRXS17 into a holdase that prevents damage caused by heat stress.

plant biology↗

bioRxiv2019

IBA endogenous auxin regulates Arabidopsis root system development in a glutathione-dependent way and is important for adaptation to phosphate deprivation.

Root system architecture results from a highly plastic developmental process to perfectly adapt to environmental conditions. In particular, the development of lateral roots (LR) and root hair (RH) growth are constantly optimized to the rhizosphere properties, including biotic and abiotic constraints. Every step of root system development is tightly controlled by auxin, the driving morphogenic hormone in plants. Glutathione, a major thiol redox regulator, is also critical for root system development but its interplay with auxin is still scarcely understood. Indeed, previous works showed that glutathione deficiency does not alter root responses to exogenous indole acetic acid (IAA), the main active auxin in plants. Because indole butyric acid (IBA), another endogenous auxinic compound, is an important source of IAA for the control of root development, we investigated the crosstalk between glutathione and IBA during root development. We show that glutathione deficiency alters LR and RH responses to exogenous IBA but not IAA. Although many efforts have been deployed, we could not identify the precise mechanism responsible for this control. However, we could show that both glutathione and IBA are required for the proper responses of RH to phosphate deprivation, suggesting an important role for this glutathione-dependent regulation of auxin pathway in plant developmental adaptation to its environment.

plant biology↗

bioRxiv2019

Arabidopsis glutathione reductase 2 is indispensable in plastids, while mitochondrial glutathione is safeguarded by additional reduction and transport systems

O_LIA highly negative glutathione redox potential (EGSH) is maintained in the cytosol, plastids and mitochondria of plant cells to support fundamental processes, including antioxidant defence, redox regulation and iron-sulfur cluster biogenesis. Out of two glutathione reductase (GR) proteins in Arabidopsis, GR2 is predicted to be dual-targeted to plastids and mitochondria, but its differential roles in these organelles remain unclear.\nC_LIO_LIWe dissected the role of GR2 in organelle glutathione redox homeostasis and plant development using a combination of genetic complementation and stacked mutants, biochemical activity studies, immunogold labelling and in vivo biosensing.\nC_LIO_LIOur data demonstrate that GR2 is dual-targeted to plastids and mitochondria, but embryo lethality of gr2 null mutants is caused specifically in plastids. Whereas lack of mitochondrial GR2 leads to a partially oxidised glutathione pool in the matrix, the ABC transporter ATM3 and the mitochondrial thioredoxin system provide functional backup and maintain plant viability.\nC_LIO_LIWe identify GR2 as essential in the plastid stroma, where it counters GSSG accumulation and developmental arrest. By contrast a functional triad of GR2, ATM3 and the thioredoxin system in the mitochondria provides resilience to excessive glutathione oxidation.\nC_LI

plant biology↗