Functional changes of OsTrxm from reductase to molecular chaperone under heat shock stress.

Ubiquitous disulfide reductases, thioredoxins (Trxs), function in the redox balance of all living organisms. Although the roles of the rice (Oryza sativa) Trx m-type isoform (OsTrxm) in chloroplast development have been already published, biochemical and molecular functions of OsTrxm remain to be elucidated for decades. The OsTrxm and its two conserved active cysteine mutant (OsTrxm C95S/C98S, referred to as OsTrxmC/S) proteins in Arabidopsis thaliana were overexpressed to characterize in vivo roles of active cysteines of OsTrxm.

The physiological role of thiol-based redox sensors in plant defense signaling.

Plants have developed multilayered defense strategies to adapt and acclimate to the kaleidoscopic environmental changes that rapidly produce reactive oxygen species (ROS) and induce redox changes. Thiol-based redox sensors containing the redox-sensitive cysteine residues act as the central machinery in plant defense signaling. Here, we review recent research on thiol-based redox sensors in plants, which perceive the changes in intracellular H O levels and activate specific downstream defense signaling.

Correction: Lee et al. Demyristoylation of the Cytoplasmic Redox Protein Trx-h2 Is Critical for Inducing a Rapid Cold Stress Response in Plants. 2021, , 1287.

In the original publication [...

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis.

Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm).

Redox-mediated structural and functional switching of C-repeat binding factors enhances plant cold tolerance.

C-repeat binding factors (CBFs) are key cold-responsive transcription factors that play pleiotropic roles in the cold acclimation, growth, and development of plants. Cold-sensitive cbf knockout mutants and cold-tolerant CBF overexpression lines exhibit abnormal phenotypes at warm temperatures, suggesting that CBF activity is precisely regulated, and a critical threshold level must be maintained for proper plant growth under normal conditions. Cold-inducible CBFs also exist in warm-climate plants but as inactive disulfide-bonded oligomers.

Demyristoylation of the Cytoplasmic Redox Protein Trx-h2 Is Critical for Inducing a Rapid Cold Stress Response in Plants.

In Arabidopsis, the cytosolic redox protein thioredoxin h2 (Trx-h2) is anchored to the cytoplasmic endomembrane through the myristoylated second glycine residue (Gly). However, under cold stress, the cytosolic Trx-h2 is rapidly translocated to the nucleus, where it interacts with and reduces the cold-responsive C-repeat-binding factors (CBFs), thus activating genes. In this study, we investigated the significance of fatty acid modification of Trx-h2 under cold conditions by generating transgenic Arabidopsis lines in the mutant background, overexpressing (Trx-h2/) and its point mutation variant [Trx-h2(G/A)/], in which the Gly was replaced by alanine (Ala).

Disulfide reductase activity of thioredoxin-h2 imparts cold tolerance in Arabidopsis.

Many thioredoxin-h (Trx-h) proteins, cytosolic isotypes of Trxs, have been functionally characterized in plants; however, the physiological function of Arabidopsis Trx-h2, which harbors two active site cysteine (Cys) residues and an N-terminal extension peptide containing a fatty acid acylation site, remains unclear. In this study, we investigated the physiological function of Trx-h2 by performing several abiotic stress treatments using trx-h1-3 knockout mutant lines, and found that the reductase function of Trx-h2 is critical for cold resistance in Arabidopsis. Plants overexpressing Trx-h2 in the trx-h2 mutant background (Trx-h2/trx-h2) showed strong cold tolerant phenotypes compared with Col-0 (wild type) and trx-h2 mutant plants.

Redox-dependent structural switch and CBF activation confer freezing tolerance in plants.

The activities of cold-responsive C-repeat-binding transcription factors (CBFs) are tightly controlled as they not only induce cold tolerance but also regulate normal plant growth under temperate conditions. Thioredoxin h2 (Trx-h2)-a cytosolic redox protein identified as an interacting partner of CBF1-is normally anchored to cytoplasmic endomembranes through myristoylation at the second glycine residue. However, after exposure to cold conditions, the demyristoylated Trx-h2 is translocated to the nucleus, where it reduces the oxidized (inactive) CBF oligomers and monomers.

Redox sensor QSOX1 regulates plant immunity by targeting GSNOR to modulate ROS generation.

Reactive oxygen signaling regulates numerous biological processes, including stress responses in plants. Redox sensors transduce reactive oxygen signals into cellular responses. Here, we present biochemical evidence that a plant quiescin sulfhydryl oxidase homolog (QSOX1) is a redox sensor that negatively regulates plant immunity against a bacterial pathogen.

Redox-Dependent Structural Modification of Nucleoredoxin Triggers Defense Responses against in .

In plants, thioredoxin (TRX) family proteins participate in various biological processes by regulating the oxidative stress response. However, their role in phytohormone signaling remains largely unknown. In this study, we investigated the functions of TRX proteins in .

The Physiological Functions of Universal Stress Proteins and Their Molecular Mechanism to Protect Plants From Environmental Stresses.

Since the original discovery of a Universal Stress Protein (USP) in , a number of USPs have been identified from diverse sources including archaea, bacteria, plants, and metazoans. As their name implies, these proteins participate in a broad range of cellular responses to biotic and abiotic stresses. Their physiological functions are associated with ion scavenging, hypoxia responses, cellular mobility, and regulation of cell growth and development.

Exploring Novel Functions of the Small GTPase Ypt1p under Heat-Shock by Characterizing a Temperature-Sensitive Mutant Yeast Strain, .

In our previous study, we found that Ypt1p, a Rab family small GTPase protein, exhibits a stress-driven structural and functional switch from a GTPase to a molecular chaperone, and mediates thermo tolerance in . In the current study, we focused on the temperature-sensitive mutant, and found that the mutant cells are highly sensitive to heat-shock, due to a deficiency in the chaperone function of Ypt1p. This defect results from an inability of the protein to form high molecular weight polymers, even though it retains almost normal GTPase function.

EMR, a cytosolic-abundant ring finger E3 ligase, mediates ER-associated protein degradation in Arabidopsis.

Investigation of the endoplasmic reticulum-associated degradation (ERAD) system in plants led to the identification of ERAD-mediating RING finger protein (EMR) as a plant-specific ERAD E3 ligase from Arabidopsis. EMR was significantly up-regulated under endoplasmic reticulum (ER) stress conditions. The EMR protein purified from bacteria displayed high E3 ligase activity, and tobacco leaf-produced EMR mediated mildew resistance locus O-12 (MLO12) degradation in a proteasome-dependent manner.

HY5, a positive regulator of light signaling, negatively controls the unfolded protein response in .

Light influences essentially all aspects of plant growth and development. Integration of light signaling with different stress response results in improvement of plant survival rates in ever changing environmental conditions. Diverse environmental stresses affect the protein-folding capacity of the endoplasmic reticulum (ER), thus evoking ER stress in plants.

The membrane-tethered NAC transcription factor, AtNTL7, contributes to ER-stress resistance in Arabidopsis.

We screened for endoplasmic reticulum (ER) stress-resistant mutants among 25 mutants of the Arabidopsis NTL (NAC with Transmembrane motif 1-Like) family. We identified a novel mutant, SALK_044777, showing strong resistance to ER stress. RT-PCR and genomic DNA sequence analyses identified the mutant as atntl7, which harbors a T-DNA insertion in the fourth exon of AtNTL7.

Stress-driven structural and functional switching of Ypt1p from a GTPase to a molecular chaperone mediates thermo tolerance in Saccharomyces cerevisiae.

Guanosine triphosphatases (GTPases) function as molecular switches in signal transduction pathways that enable cells to respond to extracellular stimuli. Saccharomyces cerevisiae yeast protein two 1 protein (Ypt1p) is a monomeric small GTPase that is essential for endoplasmic reticulum-to-Golgi trafficking. By size-exclusion chromatography, SDS-PAGE, and native PAGE, followed by immunoblot analysis with an anti-Ypt1p antibody, we found that Ypt1p structurally changed from low-molecular-weight (LMW) forms to high-molecular-weight (HMW) complexes after heat shock.

Analysis of Arabidopsis thioredoxin-h isotypes identifies discrete domains that confer specific structural and functional properties.

Multiple isoforms of Arabidopsis thaliana h-type thioredoxins (AtTrx-hs) have distinct structural and functional specificities. AtTrx-h3 acts as both a disulfide reductase and as a molecular chaperone. We prepared five representative AtTrx-hs and compared their protein structures and disulfide reductase and molecular chaperone activities.

Thioredoxin reductase type C (NTRC) orchestrates enhanced thermotolerance to Arabidopsis by its redox-dependent holdase chaperone function.

Genevestigator analysis has indicated heat shock induction of transcripts for NADPH-thioredoxin reductase, type C (NTRC) in the light. Here we show overexpression of NTRC in Arabidopsis (NTRC°(E)) resulting in enhanced tolerance to heat shock, whereas NTRC knockout mutant plants (ntrc1) exhibit a temperature sensitive phenotype. To investigate the underlying mechanism of this phenotype, we analyzed the protein's biochemical properties and protein structure.

Peroxiredoxin II is essential for preventing hemolytic anemia from oxidative stress through maintaining hemoglobin stability.

The pathophysiology of oxidative hemolytic anemia is closely associated with hemoglobin (Hb) stability; however, the mechanism of how Hb maintains its stability under oxidative stress conditions of red blood cells (RBCs) carrying high levels of oxygen is unknown. Here, we investigated the potential role of peroxiredoxin II (Prx II) in preventing Hb aggregation induced by reactive oxygen species (ROS) using Prx II knockout mice and RBCs of patients with hemolytic anemia. Upon oxidative stress, ROS and Heinz body formation were significantly increased in Prx II knockout RBCs compared to wild-type (WT), which ultimately accelerated the accumulation of hemosiderin and heme-oxygenase 1 in the Prx II knock-out livers.

Serine/threonine protein phosphatase 5 (PP5) interacts with substrate under heat stress conditions and forms protein complex in Arabidopsis.

Protein phosphatase 5 plays a pivotal role in signal transduction in animal and plant cells, and it was previously shown that Arabidopsis protein phosphatase 5 (AtPP5) performs multiple enzymatic activities that are mediated by conformational changes induced by heat shock stress. In addition, transgenic overexpression of AtPP5 gene conferred enhanced heat shock resistance compared with wild-type plant. However, the molecular mechanism underlying this enhanced heat shock tolerance through functional and conformational changes upon heat stress is not clear.

Inhibitor of apoptosis (IAP)-like protein lacks a baculovirus IAP repeat (BIR) domain and attenuates cell death in plant and animal systems.

A novel Arabidopsis thaliana inhibitor of apoptosis was identified by sequence homology to other known inhibitor of apoptosis (IAP) proteins. Arabidopsis IAP-like protein (AtILP) contained a C-terminal RING finger domain but lacked a baculovirus IAP repeat (BIR) domain, which is essential for anti-apoptotic activity in other IAP family members. The expression of AtILP in HeLa cells conferred resistance against tumor necrosis factor (TNF)-α/ActD-induced apoptosis through the inactivation of caspase activity.