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Heat stress due to global warming adversely affects plant physiology and metabolism, significantly reducing agricultural productivity. Plants have evolved various adaptive mechanisms to cope with such stresses, involving a range of heat stress-responsive proteins. This study investigates the molecular functions and structural changes of OsTDX (Oryza sativa TPR repeat-containing thioredoxin) in rice under heat stress, focusing on its roles as a disulfide reductase and molecular chaperone. OsTDX, sharing a 52 % overall amino acid identity with AtTDX, predominantly forms high molecular weight (HMW) complexes under heat stress conditions. Functional assays revealed that OsTDX exhibited increased disulfide reductase activity in a dose-dependent manner and significantly enhanced holdase chaperone activity, particularly under specific heat stress conditions (60 °C). The structural shift from low molecular weight (LMW) to HMW forms was accompanied by increased hydrophobicity, as indicated by bis-ANS fluorescence intensity measurements. In conclusion, OsTDX exhibits dual functions as a disulfide reductase and a holdase chaperone, with its chaperone activity significantly enhanced under heat stress through structural changes to HMW complexes. These findings contribute to understand the molecular mechanisms of heat tolerance in rice and highlight the potential role of OsTDX in the development of heat-tolerant crops to address crop yield declines due to global warming.
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The tomato (Solanum lycopersicum) is widely consumed globally and renowned for its health benefits, including the reduction of cardiovascular disease and prostate cancer risk. However, tomato production faces significant challenges, particularly due to various biotic stresses such as fungi, bacteria, and viruses. To address this challenges, we employed the CRISPR/Cas9 system to modify the tomato NUCLEOREDOXIN (SlNRX) genes (SlNRX1 and SlNRX2) belonging to the nucleocytoplasmic THIOREDOXIN subfamily. CRISPR/Cas9-mediated mutations in SlNRX1 (slnrx1) plants exhibited resistance against bacterial leaf pathogen Pseudomonas syringae pv. maculicola (Psm) ES4326, as well as the fungal pathogen Alternaria brassicicola. However, the slnrx2 plants did not display resistance. Notably, the slnrx1 demonstrated elevated levels of endogenous salicylic acid (SA) and reduced levels of jasmonic acid after Psm infection, in comparison to both wild-type (WT) and slnrx2 plants. Furthermore, transcriptional analysis revealed that genes involved in SA biosynthesis, such as ISOCHORISMATE SYNTHASE 1 (SlICS1) and ENHANCED DISEASE SUSCEPTIBILITY 5 (SlEDS5), were upregulated in slnrx1 compared to WT plants. In addition, a key regulator of systemic acquired resistance, PATHOGENESIS-RELATED 1 (PR1), exhibited increased expression in slnrx1 compared to WT. These findings suggest that SlNRX1 acts as a negative regulator of plant immunity, facilitating infection by the Psm pathogen through interference with the phytohormone SA signaling pathway. Thus, targeted mutagenesis of SlNRX1 is a promising genetic means to enhance biotic stress resistance in crop breeding.
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Ácido Salicílico , Solanum lycopersicum , Ácido Salicílico/metabolismo , Solanum lycopersicum/genética , Melhoramento Vegetal , Pseudomonas syringae/fisiologia , Transdução de Sinais/genética , Ciclopentanos/metabolismo , Doenças das Plantas/microbiologia , Regulação da Expressão Gênica de PlantasRESUMO
The DNA-binding protein from starved cells, known as DPS, has been characterized as a crucial factor in protecting E. coli from external stresses. The DPS functions in various cellular processes, including protein-DNA binding, ferroxidase activity, compaction of chromosome and regulation of stress resistance gene expression. DPS proteins exist as oligomeric complexes; however, the specific biochemical activity of oligomeric DPS in conferring heat shock tolerance has not been fully understood. Therefore, we investigated the novel functional role of DPS under heat shock. To elucidate the functional role of DPS under heat shock conditions, we purified recombinant GST-DPS protein and demonstrated its thermostability and existence in its highly oligomeric form. Furthermore, we discovered that the hydrophobic region of GST-DPS influenced the formation of oligomers, which exhibited molecular chaperone activity, thereby preventing the aggregation of substrate proteins. Collectively, our findings highlight the novel functional role of DPS, as a molecular chaperone and may confer thermotolerance to E. coli.
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Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Ligação a DNA/metabolismo , Chaperonas Moleculares/metabolismo , Proteínas de Escherichia coli/metabolismo , Resposta ao Choque Térmico , Proteínas de Bactérias/metabolismo , Proteínas da Membrana Bacteriana Externa/genéticaRESUMO
In the original publication [...].
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Profilins (PFNs) are actin monomer-binding proteins that function as antimicrobial agents in plant phloem sap. Although the roles of Arabidopsis thaliana profilin protein isoforms (AtPFNs) in regulating actin polymerization have already been described, their biochemical and molecular functions remain to be elucidated. Interestingly, a previous study indicated that AtPFN2 with high molecular weight (HMW) complexes showed lower antifungal activity than AtPFN1 with low molecular weight (LMW). These were bacterially expressed and purified to characterize the unknown functions of AtPFNs with different structures. In this study, we found that AtPFN1 and AtPFN2 proteins have LMW and HMW structures, respectively, but only AtPFN2 has a potential function as a molecular chaperone, which has never been reported elsewhere. AtPFN2 has better protein stability than AtPFN1 due to its higher molecular weight under heat shock conditions. The function of AtPFN2 as a holdase chaperone predominated in the HMW complexes, whereas the chaperone function of AtPFN1 was not observed in the LMW forms. These results suggest that AtPFN2 plays a critical role in plant tolerance by increasing hydrophobicity due to external heat stress.
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Arabidopsis , Actinas/metabolismo , Antifúngicos/metabolismo , Arabidopsis/metabolismo , Resposta ao Choque Térmico , Proteínas dos Microfilamentos/metabolismo , Chaperonas Moleculares/metabolismo , Plantas/metabolismo , Profilinas/genéticaRESUMO
Environmental stresses restrict plant growth and development and decrease crop yield. The circadian clock is associated with the ability of a plant to adapt to daily environmental fluctuations and the production and consumption of energy. Here, we investigated the role of Arabidopsis Universal Stress Protein (USP; At3g53990) in the circadian regulation of nuclear clock genes. The Arabidopsis usp knockout mutant line exhibited critically diminished circadian amplitude of the central oscillator CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) but enhanced the amplitude of TIMING OF CAB EXPRESSION 1 (TOC1). However, the expression of USP under the control of its own promoter restored the circadian timing of both genes, suggesting that USP regulates the circadian rhythm of Arabidopsis central clock genes, CCA1 and TOC1.
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Proteínas de Arabidopsis , Arabidopsis , Relógios Circadianos , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Relógios Circadianos/genética , Ritmo Circadiano/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Choque Térmico/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
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. However, upon translocation to the nucleus under a cold snap, the h2-isotype of cytosolic thioredoxin (Trx-h2), reduces the oxidized (inactive) CBF oligomers and the newly synthesized CBF monomers, thus producing reduced (active) CBF monomers. Thus, the redox-dependent structural switching and functional activation of CBFs protect plants under cold stress.
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Proteínas de Arabidopsis , Arabidopsis , Temperatura Baixa , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/fisiologia , Resposta ao Choque Frio/genética , Regulação da Expressão Gênica de Plantas , OxirreduçãoRESUMO
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 cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.
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Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Estresse do Retículo Endoplasmático , Regulação da Expressão Gênica de Plantas , Transdução de Sinal Luminoso , Ubiquitina-Proteína Ligases/metabolismo , Resposta a Proteínas não Dobradas , Proteínas de Arabidopsis/genética , Ubiquitina-Proteína Ligases/genéticaRESUMO
In Arabidopsis, the cytosolic redox protein thioredoxin h2 (Trx-h2) is anchored to the cytoplasmic endomembrane through the myristoylated second glycine residue (Gly2). 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 cold-responsive (COR) 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 trx-h2 mutant background, overexpressing Trx-h2 (Trx-h2OE/trx-h2) and its point mutation variant Trx-h2(G/A) [Trx-h2(G/A)OE/trx-h2], in which the Gly2 was replaced by alanine (Ala). Due to the lack of Gly2, Trx-h2(G/A) was incapable of myristoylation, and a part of Trx-h2(G/A) localized to the nucleus even under warm temperature. As no time is spent on the demyristoylation and subsequent nuclear translocation of Trx-h2(G/A) under a cold snap, the ability of Trx-h2(G/A) to protect plants from cold stress was greater than that of Trx-h2. Additionally, COR genes were up-regulated earlier in Trx-h2(G/A)2OE/trx-h2 plants than in Trx-h2OE/trx-h2 plants under cold stress. Consequently, Trx-h2(G/A)2OE/trx-h2 plants showed greater cold tolerance than Col-0 (wild type) and Trx-h2OE/trx-h2 plants. Overall, our results clearly demonstrate the significance of the demyristoylation of Trx-h2 in enhancing plant cold/freezing tolerance.
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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-h2OE/trx-h2) showed strong cold tolerant phenotypes compared with Col-0 (wild type) and trx-h2 mutant plants. By contrast, Trx-h2(C/S)OE/trx-h2 plants expressing a variant Trx-h2 protein, in which both active site Cys residues were substituted by serine (Ser) residues, showed high cold sensitivity, similar to trx-h2 plants. Moreover, cold-responsive (COR) genes were highly up-regulated in Trx-h2OE/trx-h2 plants but not in trx-h2 and Trx-h2(C/S)OE/trx-h2 plants under cold conditions. These results explicitly suggest that the cytosolic Trx-h2 protein relays the external cold stress signal to downstream cold defense signaling cascades through its protein disulfide reductase function.
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Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Tiorredoxina h/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Resposta ao Choque Frio , Regulação da Expressão Gênica de Plantas , Oxirredução , Tiorredoxina h/genéticaRESUMO
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 conditions1-4. 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 residue5,6. 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. The reduced (active) monomers activate cold-regulated gene expression. Thus, in contrast to the Arabidopsis trx-h2 (AT5G39950) null mutant, Trx-h2 overexpression lines are highly cold tolerant. Our findings reveal the mechanism by which cold-mediated redox changes induce the structural switching and functional activation of CBFs, therefore conferring plant cold tolerance.
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Arabidopsis/genética , Arabidopsis/fisiologia , Temperatura Baixa , Resposta ao Choque Frio/genética , Resposta ao Choque Frio/fisiologia , Oxirredução , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologiaRESUMO
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. The expression level of QSOX1 is inversely correlated with pathogen-induced reactive oxygen species (ROS) accumulation. Interestingly, QSOX1 both senses and regulates ROS levels by interactingn with and mediating redox regulation of S-nitrosoglutathione reductase, which, consistent with previous findings, influences reactive nitrogen-mediated regulation of ROS generation. Collectively, our data indicate that QSOX1 is a redox sensor that negatively regulates plant immunity by linking reactive oxygen and reactive nitrogen signaling to limit ROS production.
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Aldeído Oxirredutases/metabolismo , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/metabolismo , Imunidade Vegetal , Espécies Reativas de Oxigênio/metabolismo , Aldeído Oxirredutases/genética , Fenômenos Biológicos , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/genética , Plantas/imunologia , Plantas/metabolismo , Transdução de SinaisRESUMO
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 Arabidopsis thaliana. Quantitative polymerase chain reaction (qPCR) experiments revealed that the expression of ARABIDOPSIS NUCLEOREDOXIN 1 (AtNRX1) is specifically induced by the application of jasmonic acid (JA) and upon inoculation with a necrotrophic fungal pathogen, Alternaria brassicicola. The AtNRX1 protein usually exists as a low molecular weight (LMW) monomer and functions as a reductase, but under oxidative stress AtNRX1 transforms into polymeric forms. However, the AtNRX1M3 mutant protein, harboring four cysteine-to-serine substitutions in the TRX domain, did not show structural modification under oxidative stress. The Arabidopsisatnrx1 null mutant showed greater resistance to A. brassicicola than wild-type plants. In addition, plants overexpressing both AtNRX1 and AtNRX1M3 were susceptible to A. brassicicola infection. Together, these findings suggest that AtNRX1 normally suppresses the expression of defense-responsive genes, as if it were a safety pin, but functions as a molecular sensor through its redox-dependent structural modification to induce disease resistance in plants.
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Alternaria/fisiologia , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Resistência à Doença , Interações Hospedeiro-Patógeno , Oxirredução , Oxirredutases/metabolismo , Sequência de Aminoácidos , Oxirredutases/química , Fenótipo , Doenças das Plantas/microbiologia , Ligação Proteica , Multimerização Proteica , Transporte ProteicoRESUMO
Since the original discovery of a Universal Stress Protein (USP) in Escherichia coli, 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. Consistent with their roles in resistance to multiple stresses, USPs show a wide range of structural diversity that results from the diverse range of other functional motifs fused with the USP domain. As well as providing structural diversity, these catalytic motifs are responsible for the diverse biochemical properties of USPs and enable them to act in a number of cellular signaling transducers and metabolic regulators. Despite the importance of USP function in many organisms, the molecular mechanisms by which USPs protect cells and provide stress resistance remain largely unknown. This review addresses the diverse roles of USPs in plants and how the proteins enable plants to resist against multiple stresses in ever-changing environment. Bioinformatic tools used for the collection of a set of USPs from various plant species provide more than 2,100 USPs and their functional diversity in plant physiology. Data from previous studies are used to understand how the biochemical activity of plant USPs modulates biotic and abiotic stress signaling. As USPs interact with the redox protein, thioredoxin, in Arabidopsis and reactive oxygen species (ROS) regulates the activity of USPs, the involvement of USPs in redox-mediated defense signaling is also considered. Finally, this review discusses the biotechnological application of USPs in an agricultural context by considering the development of novel stress-resistant crops through manipulating the expression of USP genes.
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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 Saccharomyces cerevisiae. In the current study, we focused on the temperature-sensitive ypt1-G80D mutant, and found that the mutant cells are highly sensitive to heat-shock, due to a deficiency in the chaperone function of Ypt1pG80D. This defect results from an inability of the protein to form high molecular weight polymers, even though it retains almost normal GTPase function. The heat-stress sensitivity of ypt1-G80D cells was partially recovered by treatment with 4-phenylbutyric acid, a chemical chaperone. These findings indicate that loss of the chaperone function of Ypt1pG80D underlies the heat sensitivity of ypt1-G80D cells. We also compared the proteomes of YPT1 (wild-type) and ypt1-G80D cells to investigate Ypt1p-controlled proteins under heat-stress conditions. Our findings suggest that Ypt1p controls an abundance of proteins involved in metabolism, protein synthesis, cellular energy generation, stress response, and DNA regulation. Finally, we suggest that Ypt1p essentially regulates fundamental cellular processes under heat-stress conditions by acting as a molecular chaperone.
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Resposta ao Choque Térmico , Proteínas de Saccharomyces cerevisiae/metabolismo , Termotolerância , Proteínas rab de Ligação ao GTP/metabolismo , Mutação de Sentido Incorreto , Fenilbutiratos/farmacologia , Multimerização Proteica , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas rab de Ligação ao GTP/genéticaRESUMO
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. Subcellular localization and coimmunoprecipitation analyses showed that EMR forms a complex with ubiquitin-conjugating enzyme 32 (UBC32) as a cytosolic interaction partner. Mutation of EMR and RNA interference (RNAi) increased the tolerance of plants to ER stress. EMR RNAi in the bri1-5 background led to partial recovery of the brassinosteroid (BR)-insensitive phenotypes as compared with the original mutant plants and increased ER stress tolerance. The presented results suggest that EMR is involved in the plant ERAD system that affects BR signaling under ER stress conditions as a novel Arabidopsis ring finger E3 ligase mainly present in cytosol while the previously identified ERAD E3 components are typically membrane-bound proteins.
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Aciltransferases/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Citosol/metabolismo , Degradação Associada com o Retículo Endoplasmático , Proteólise , Domínios RING Finger , Ubiquitina-Proteína Ligases/metabolismo , Aciltransferases/genética , Adaptação Fisiológica , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Brassinosteroides/metabolismo , Estresse do Retículo Endoplasmático , Regulação da Expressão Gênica de Plantas , Fenótipo , Transporte Proteico , Interferência de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais , Enzimas de Conjugação de Ubiquitina/metabolismoRESUMO
Maintenance of homeostasis of the endoplasmic reticulum (ER) ensures the balance between loading of nascent proteins and their secretion. Certain developmental conditions or environmental stressors affect protein folding causing ER stress. The resultant ER stress is mitigated by upregulating a set of stress-responsive genes in the nucleus modulating the mechanism of the unfolded protein response (UPR). In plants, the UPR is mediated by two major pathways; by the proteolytic processing of bZIP17/28 and by the IRE1-mediated splicing of bZIP60 mRNA. Recent studies have shown the involvement of plant-specific NAC transcription factors in UPR regulation. The molecular mechanisms activating plant-UPR transducers are only recently being unveiled. This review focuses on important structural features involved in the activation of the UPR transducers like bZIP17/28/60, IRE1, BAG7, and NAC017/062/089/103. Also, we discuss the activation of the UPR pathways, including BAG7-bZIP28 and IRE1-bZIP60, in detail, together with the NAC-TFs, which adds a new paradigm to the plant UPR.
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SIGNIFICANCE: Sessile plants respond to oxidative stress caused by internal and external stimuli by producing diverse forms of enzymatic and nonenzymatic antioxidant molecules. Peroxiredoxins (Prxs) in plants, including the Prx1, Prx5, Prx6, and PrxQ isoforms, constitute a family of antioxidant enzymes and play important functions in cells. Each Prx localizes to a specific subcellular compartment and has a distinct function in the control of plant growth, development, cellular metabolism, and various aspects of defense signaling. Recent Advances: Prx1, a typical Prx in plant chloroplasts, has redox-dependent multiple functions. It acts as a hydrogen peroxide (H2O2)-catalyzing peroxidase, a molecular chaperone, and a biological circadian marker. Prx1 undergoes a functional switching from a peroxidase to a molecular chaperone in response to oxidative stress, concomitant with the structural changes from a low-molecular-weight species to high-molecular-weight complexes mediated by the post-translational modification of its active site Cys residues. The redox status of the protein oscillates diurnally between hyperoxidation and reduction, showing a circadian rhythmic output. These dynamic structural and functional transformations mediate the effect of plant Prx1 on protecting plants from a myriad of harsh environmental stresses. CRITICAL ISSUES: The multifunctional diversity of plant Prxs and their roles in cellular defense signaling depends on their specific interaction partners, which remain largely unidentified. Therefore, the identification of Prx-interacting proteins is necessary to clarify their physiological significance. FUTURE DIRECTIONS: Since the functional specificity of the four plant Prx isoforms remains unclear, future studies should focus on investigating the physiological importance of each Prx isotype. Antioxid. Redox Signal. 28, 625-639.
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Peróxido de Hidrogênio/metabolismo , Chaperonas Moleculares/metabolismo , Peroxidase/metabolismo , Peroxirredoxinas/metabolismo , Antioxidantes/metabolismo , Cloroplastos/metabolismo , Oxirredução , Estresse Oxidativo/genética , Peroxirredoxinas/genética , Plantas/genética , Plantas/metabolismo , Estresse Fisiológico/genéticaRESUMO
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. Consequently, the unfolded protein response (UPR), in which a set of molecular chaperones is expressed, is initiated in the ER to alleviate this stress. Although its underlying molecular mechanism remains unknown, light is believed to be required for the ER stress response. In this study, we demonstrate that increasing light intensity elevates the ER stress sensitivity of plants. Moreover, mutation of the ELONGATED HYPOCOTYL 5 (HY5), a key component of light signaling, leads to tolerance to ER stress. This enhanced tolerance of hy5 plants can be attributed to higher expression of UPR genes. HY5 negatively regulates the UPR by competing with basic leucine zipper 28 (bZIP28) to bind to the G-box-like element present in the ER stress response element (ERSE). Furthermore, we found that HY5 undergoes 26S proteasome-mediated degradation under ER stress conditions. Conclusively, we propose a molecular mechanism of crosstalk between the UPR and light signaling, mediated by HY5, which positively mediates light signaling, but negatively regulates UPR gene expression.