Lipid-lowering medications and risk of malignant melanoma: a Mendelian randomization study.

Background: The relationship between blood lipids, lipid-modifying medications, and cancer risk has been under investigation for some time. Recent studies suggest that lipid-lowering medications might influence melanoma outcomes, though findings remain controversial. Our study aims to clarify the potential causal relationship between lipid-lowering drugs commonly used and melanoma incidence through a comprehensive Mendelian randomization (MR) analysis. Methods: Genetic variations within an LDL-related drug target gene (LDL-cholesterol from a genome-wide association study) served as proxies for exposure to lipid-lowering drugs. We conducted a two-sample Mendelian randomization analysis using inverse variance weighting (IVW), MR-Egger, and weighted median approaches. The MR-PRESSO test and pleiotropy_test were utilized to identify and adjust for horizontal pleiotropy. Stability and reliability of the Mendelian randomization findings were assessed using the leave-one-out method, Cochran's Q test, and funnel plot analysis. Odds ratios (OR) were employed to evaluate the causal relationship between genetic proxies of lipid-lowering drugs and melanoma risk. Results: IVW analysis revealed that HMGCR gene expression is linked to a decreased risk of melanoma [OR: 0.624(0.439-0.888); p = 0.008]. Conversely, PCSK9 gene expression is tied to an elevated risk of melanoma [OR: 1.233(1.026-1.484); p = 0.025]. No significant association was observed between NPC1L1 and melanoma. Conclusions: HMGCR inhibitors (statins) may increase melanoma risk, while PCSK9 inhibitors (evolocumab, alirocumab) could potentially decrease melanoma risk.

Simplified Protocol to Demonstrate Gene Expression in Nicotiana benthamiana Using an Agrobacterium-Mediated Transient Assay.

Agrobacterium-mediated transient gene expression in Nicotiana benthamiana is widely used to study gene function in plants. One dramatic phenotype that is frequently screened for is cell death. Here, we present a simplified protocol for Agrobacterium-mediated transient gene expression by infiltration. Compared with current methods, the novel protocol can be done without a centrifuge or spectrometer, thereby suitable for K-12 outreach programs as well as rapidly identifying genes that induce cell death. Key features • The protocol simplifies the widely used Agrobacterium-mediated transient gene expression assay [1] and can be completed within one week when plants are available. • Rice XB3 gene can induce a dramatic and easily identifiable cell death phenotype in Nicotiana benthamiana. • Allows identification of cell death-inducing genes and is suitable for teaching. • Compared to the currently used methods, our protocol omits the use of agroinfiltration buffer, pH meter, temperature-controlled growth chamber, centrifuge, and spectrophotometer. Graphical overview Agrobacterium infiltration (agroinfiltration) of Nicotiana benthamiana. The photo demonstrates the method of agroinfiltration into the abaxial side of leaves using a needleless syringe.

Analysis of risk factors of lower extremity deep venous thrombosis in patients undergoing hepatobiliary surgery.

This study analyzed records of 200 patients who underwent hepatobiliary surgery to identify factors that contribute to lower extremity venous thromboembolism (VTE). 19 patients (9.50%) developed lower extremity deep vein thrombosis. Univariate analysis revealed significant differences between the study group and the control group in terms of age, body mass index, previous thromboembolic history, hypertension, type 2 diabetes, hyperlipidemia, smoking history, times of lower extremity venipuncture, operation time, postoperative bedrest time, postoperative platelet count, postoperative D-dimer level, and postoperative C-reactive protein level (P<0.05). Multivariable logistic regression analysis identified age ≥60 years, body mass index ≥24 kg/m2, previous history of thromboembolism, hypertension, type 2 diabetes mellitus, hyperlipidemia, smoking history, number of lower extremity venipunctures ≥5, operation time ≥2 hours, postoperative bedrest time ≥48 hours, postoperative blood platelet count ≥300×109/L, postoperative D-dimer level ≥200 g/L, and postoperative C-reactive protein ≥8.0 mg/L as significant predisposing factors for lower extremity VTE. The study concludes that patients undergoing hepatobiliary surgery are at an increased risk of developing lower extremity VTE, and prevention strategies must be tailored to each patient's unique set of risk factors. This includes careful management of postoperative bed rest, monitoring of platelet count, D-dimer and C-reactive protein levels, controlling hypertension, type 2 diabetes mellitus, hyperlipidemia, and cessation of smoking. This study highlights the importance of early identification of patients at high risk of lower extremity VTE following hepatobiliary surgery and comprehensive prevention measures.

Understanding of supramolecular solution polymerization and interfacial polymerization via forming multiple hydrogen bonds: a computer simulation study.

By employing dissipative particle dynamics (DPD) simulations combined with stochastic polymerization models, we have conducted a detailed simulation study of supramolecular solution polymerization as well as interfacial polymerization employing a coarse-grained model which is closer to the real monomer structure. By adding bending angle potentials to coarse-grained models representing supramolecular reactive monomers, we achieved monomer model simulations for different kinds of multiple hydrogen bonds. Our simulation results indicated that for the interfacial polymerization system, the volume of the monomer caused a strong steric hindrance effect, which in turn led to a low average degree of polymerization of the product. Therefore, by appropriately reducing the volume of the reaction monomer (corresponding to different confinement ascribed to the multiple hydrogen bonds), the average polymerization degree, the degree of reaction and the polymerization rate of the monomer can be effectively improved. For the solution polymerization system and the interfacial polymerization system, a certain proportion of rigid monomers and flexible monomers (60% rigid monomers and 40% flexible monomers) are mixed. High molecular weight products can thus be obtained via the polymerization reaction. The simulation strategy proposed in this study can not only provide theoretical guidance for better design of new supramolecular systems, but also provide ideas for the further synthesis of higher molecular weight supramolecular polymers.

Protein complex formation in methionine chain-elongation and leucine biosynthesis.

During the past two decades, glucosinolate (GLS) metabolic pathways have been under extensive studies because of the importance of the specialized metabolites in plant defense against herbivores and pathogens. The studies have led to a nearly complete characterization of biosynthetic genes in the reference plant Arabidopsis thaliana. Before methionine incorporation into the core structure of aliphatic GLS, it undergoes chain-elongation through an iterative three-step process recruited from leucine biosynthesis. Although enzymes catalyzing each step of the reaction have been characterized, the regulatory mode is largely unknown. In this study, using three independent approaches, yeast two-hybrid (Y2H), coimmunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC), we uncovered the presence of protein complexes consisting of isopropylmalate isomerase (IPMI) and isopropylmalate dehydrogenase (IPMDH). In addition, simultaneous decreases in both IPMI and IPMDH activities in a leuc:ipmdh1 double mutants resulted in aggregated changes of GLS profiles compared to either leuc or ipmdh1 single mutants. Although the biological importance of the formation of IPMI and IPMDH protein complexes has not been documented in any organisms, these complexes may represent a new regulatory mechanism of substrate channeling in GLS and/or leucine biosynthesis. Since genes encoding the two enzymes are widely distributed in eukaryotic and prokaryotic genomes, such complexes may have universal significance in the regulation of leucine biosynthesis.

Rice immune sensor XA21 differentially enhances plant growth and survival under distinct levels of drought.

Drought is a complex stress that limits plant growth and crop production worldwide. The mechanisms by which plants coordinately respond to distinct levels of water deficits (e.g., mild, moderate or severe drought) remain elusive. Here we demonstrate that the rice immune sensor XA21 promotes survival of rice seedlings during dehydration stress. XA21 expression increases deposition of lignin and cellulose in the xylem vessels and their surrounding cells. Inhibition of aquaporin water channels by mercuric chloride eliminates XA21-mediated dehydration survival, suggesting that XA21 enables plant survival during drought, probably by protecting xylem functionality. In contrast to prevailing observations of stress tolerance genes, XA21 is also capable of enhancing rice growth during moderate drought. Thus, XA21 acts as a mediator for stress protection and plant growth under water-limiting conditions.

Analysis of the clinical characteristics of thirteen patients with Weber-Christian panniculitis.

BACKGROUND: Weber-Christian disease (WCD) is an uncommon, idiopathic disease that is challenging to diagnose and has an unclear treatment protocol. We reviewed thirteen patients with WCD and analyzed their clinical characteristics. The purpose of this article was to improve the understanding of this rare disorder. METHODS: Thirteen cases of WCD were analyzed retrospectively regarding their clinical manifestation, laboratory results, misdiagnoses, therapy, and outcome. RESULTS: Of the thirteen patients diagnosed with WCD, the majority were female (male to female ratio, 2:11), with a mean patient age of 50.1 years. Subcutaneous nodules were the most commonly reported symptom, followed by fever, arthralgias/arthritis, and myalgia. The laboratory results were typically nonspecific. In total, 61.5% patients were misdiagnosed before pathology confirmed the diagnosis of WCD. Most patients were treated with corticosteroids and/or immunosuppressants. Two patients were treated surgically. While long-term remission was successfully achieved in some patients, others had recurrent symptoms. CONCLUSION: WCD was predominantly observed in female patients in our cohort. Subcutaneous nodules and fever were the most common clinical characteristics. In addition, the patients' laboratory test results were nonspecific, which led to a high misdiagnosis rate. In this study population, corticosteroid and/or immunosuppressant treatments were efficacious therapeutic interventions for WCD.Key Points•Subcutaneous nodules and fever were the most common clinical characteristics in Weber-Christian panniculitis.•Misdiagnosis rate was higher in Weber-Christian panniculitis patient; tumors, bacterial infections and rheumatic diseases were the most common misdiagnoses.•Corticosteroid and/or immunosuppressant therapy was effective in most Weber-Christian panniculitis patients.

Proteomic characterization of MPK4 signaling network and putative substrates.

KEY MESSAGE: Combining genetic engineering of MPK4 activity and quantitative proteomics, we established an in planta system that enables rapid study of MPK4 signaling networks and potential substrate proteins. Mitogen activated protein kinase 4 (MPK4) is a multifunctional kinase that regulates various signaling events in plant defense, growth, light response and cytokinesis. The question of how a single protein modulates many distinct processes has spurred extensive research into the physiological outcomes resulting from genetic perturbation of MPK4. However, the mechanism by which MPK4 functions is still poorly understood due to limited data on the MPK4 networks including substrate proteins and downstream pathways. Here we introduce an experimental system that combines genetic engineering of kinase activity and quantitative proteomics to rapidly study the signaling networks of MPK4. First, we transiently expressed a constitutively active (MPK4CA) and an inactive (MPK4IN) version of a Brassica napus MPK4 (BnMPK4) in Nicotiana benthamiana leaves. Proteomics analysis revealed that BnMPK4 activation affects multiple pathways (e.g., metabolism, redox regulation, jasmonic acid biosynthesis and stress responses). Furthermore, BnMPK4 activation also increased protein phosphorylation in the phosphoproteome, from which putative MPK4 substrates were identified. Using protein kinase assay, we validated that a transcription factor TCP8-like (TCP8) and a PP2A regulatory subunit TAP46-like (TAP46) were indeed phosphorylated by BnMPK4. Taken together, we demonstrated the utility of proteomics and phosphoproteomics in elucidating kinase signaling networks and in identification of downstream substrates.

Effects of Annealing on the Residual Stress in γ-TiAl Alloy by Molecular Dynamics Simulation.

In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, the relationship between microstructure and residual stress is investigated. The results show that there is no phase transition during annealing, but atom distortion occurs with the change of temperature, and the average grain size slightly increases after annealing. There are some atom clusters in the grains, with a few point defects, and the point defect concentration increases with the rise in temperature, and vice versa; the higher the annealing temperature, the fewer the point defects in the grain after annealing. Due to the grain boundary volume shrinkage and and an increase in the plastic deformation of the grain boundaries during cooling, stress is released, and the average residual stress along Y and Z directions after annealing is less than the average residual stress after prepressing.

Characterization of thiol-based redox modifications of Brassica napusSNF1-related protein kinase 2.6-2C.

Sucrose nonfermenting 1-related protein kinase 2.6 (SnRK2.6), also known as Open Stomata 1 (OST1) in Arabidopsis thaliana, plays a pivotal role in abscisic acid (ABA)-mediated stomatal closure. Four SnRK2.6 paralogs were identified in the Brassica napus genome in our previous work. Here we studied one of the paralogs, BnSnRK2.6-2C, which was transcriptionally induced by ABA in guard cells. Recombinant BnSnRK2.6-2C exhibited autophosphorylation activity and its phosphorylation sites were mapped. The autophosphorylation activity was inhibited by S-nitrosoglutathione (GSNO) and by oxidized glutathione (GSSG), and the inhibition was reversed by reductants. Using monobromobimane (mBBr) labeling, we demonstrated a dose-dependent modification of BnSnRK2.6-2C by GSNO. Furthermore, mass spectrometry analysis revealed previously uncharacterized thiol-based modifications including glutathionylation and sulfonic acid formation. Of the six cysteine residues in BnSnRK2.6-2C, C159 was found to have different types of thiol modifications, suggesting its high redox sensitivity and versatility. In addition, mBBr labeling on tyrosine residues was identified. Collectively, these data provide detailed biochemical characterization of redox-induced modifications and changes of the BnSnRK2.6-2C activity.

A Phosphorylation Switch on Lon Protease Regulates Bacterial Type III Secretion System in Host.

Most pathogenic bacteria deliver virulence factors into host cytosol through type III secretion systems (T3SS) to perturb host immune responses. The expression of T3SS is often repressed in rich medium but is specifically induced in the host environment. The molecular mechanisms underlying host-specific induction of T3SS expression is not completely understood. Here we demonstrate in Xanthomonas citri that host-induced phosphorylation of the ATP-dependent protease Lon stabilizes HrpG, the master regulator of T3SS, conferring bacterial virulence. Ser/Thr/Tyr phosphoproteome analysis revealed that phosphorylation of Lon at serine 654 occurs in the citrus host. In rich medium, Lon represses T3SS by degradation of HrpG via recognition of its N terminus. Genetic and biochemical data indicate that phosphorylation at serine 654 deactivates Lon proteolytic activity and attenuates HrpG proteolysis. Substitution of alanine for Lon serine 654 resulted in repression of T3SS gene expression in the citrus host through robust degradation of HrpG and reduced bacterial virulence. Our work reveals a novel mechanism for distinct regulation of bacterial T3SS in different environments. Additionally, our data provide new insight into the role of protein posttranslational modification in the regulation of bacterial virulence.IMPORTANCE Type III secretion systems (T3SS) are an essential virulence trait of many bacterial pathogens because of their indispensable role in the delivery of virulence factors. However, expression of T3SS in the noninfection stage is energy consuming. Here, we established a model to explain the differential regulation of T3SS in host and nonhost environments. When Xanthomonas cells are grown in rich medium, the T3SS regulator HrpG is targeted by Lon protease for proteolysis. The degradation of HrpG leads to downregulated expression of HrpX and the hrp/hrc genes. When Xanthomonas cells infect the host, specific plant stimuli can be perceived and induce Lon phosphorylation at serine 654. Phosphorylation on Lon attenuates its proteolytic activity and protects HrpG from degradation. Consequently, enhanced stability of HrpG activates HrpX and turns on bacterial T3SS in the host. Our work provides a novel molecular mechanism underlying host-dependent activation of bacterial T3SS.

Identification of potential metabolic biomarkers of cerebrospinal fluids that differentiate tuberculous meningitis from other types of meningitis by a metabolomics study.

Tuberculous meningitis (TBM) is caused by tuberculosis infection of of the meninges, which are the membrane systems that encircle the brain, with a high morbidity and mortality rate. It is challenging to diagnose TBM among other types of meningitis, such as viral meningitis, bacterial meningitis and cryptococcal meningitis. We aimed to identify metabolites that are differentially expressed between TBM and the other types of meningitis by a global metabolomics analysis. The cerebrospinal fluids (CSF) from 50 patients with TBM, 17 with viral meningitis, 17 with bacterial meningitis, and 16 with cryptococcal meningitis were analyzed using ultra high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS). A total of 1161 and 512 features were determined in positive and negative electrospray ionization mode, respectively. A clear separation between TBM and viral, bacterial or cryptococcal meningitis was achieved by orthogonal projections to latent structures-discriminate analysis (OPLS-DA) analysis. Potential metabolic markers and related pathways were identified, which were mainly involved in the metabolism of amino acid, lipids and nucleosides. In summary, differential metabolic profiles of the CSF exist between TBM and other types of meningitis, and potential metabolic biomarkers were identified to differentiate TBM from other types of meningitis.

Old age and hydrocephalus are associated with poor prognosis in patients with tuberculous meningitis: A retrospective study in a Chinese adult population.

Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis with a very poor prognosis. We aimed at assessing risk factors related to the prognosis of patients with TBM.Forty-five inpatients with TBM in our institution from January 2013 to December 2015 were enrolled retrospectively. The good or poor prognosis in the patients was defined, based on Glasgow Outcome Scale System at discharge. Patients with a GOS score less than 5 were defined as "poor prognosis." Univariate and multivariate logistic regression analyses were performed to assess the predictors for TBM outcome.Among 45 TBM patients, 35 (77.8%) and 10 (22.2%) were in good, poor prognoses, respectively. Old age, disturbance of consciousness, moderate to severe electroencephalogram abnormality, hydrocephalus, remarkable increase of protein (≥ 236 mg/dL) and white blood cell counts (≥ 243 /µL) in cerebral spinal fluid were associated with poor prognosis. Multivariate analysis indicated that old age (odds ratio (OR) = 18.395, P = .036) and hydrocephalus (OR = 32.995, P = .049) were independent factors for a poor outcome of TBM.In conclusion, old age and hydrocephalus are the predictors for poor prognosis of TBM. Patients with these risk factors should be treated promptly with a special care paid to improve their outcomes.

Redox regulation of a guard cell SNF1-related protein kinase in Brassica napus, an oilseed crop.

Kinase-mediated phosphorylation is a pivotal regulatory process in stomatal responses to stresses. Through a redox proteomics study, a sucrose non-fermenting 1-related protein kinase (SnRK2.4) was identified to be redox-regulated in Brassica napus guard cells upon abscisic acid treatment. There are six genes encoding SnRK2.4 paralogs in B. napus Here, we show that recombinant BnSnRK2.4-1C exhibited autophosphorylation activity and preferentially phosphorylated the N-terminal region of B. napus slow anion channel (BnSLAC1-NT) over generic substrates. The in vitro activity of BnSnRK2.4-1C requires the presence of manganese (Mn2+). Phosphorylation sites of autophosphorylated BnSnRK2.4-1C were mapped, including serine and threonine residues in the activation loop. In vitro BnSnRK2.4-1C autophosphorylation activity was inhibited by oxidants such as H2O2 and recovered by active thioredoxin isoforms, indicating redox regulation of BnSnRK2.4-1C. Thiol-specific isotope tagging followed by mass spectrometry analysis revealed specific cysteine residues responsive to oxidant treatments. The in vivo activity of BnSnRK2.4-1C is inhibited by 15 min of H2O2 treatment. Taken together, these data indicate that BnSnRK2.4-1C, an SnRK preferentially expressed in guard cells, is redox-regulated with potential roles in guard cell signal transduction.

Peliosis hepatis: 2 case reports of a rare liver disorder and its differential diagnosis.

RATIONALE: Peliosis hepatis (PH) is a rare tumor-like liver lesion composed of multiple blood-filled cavities within the liver parenchyma. It is hard to differentiate PH from other liver lesions by imaging, such as carcinoma, metastases, or abscess. PATIENT CONCERNS: Here, we reported 2 cases that presented with liver lesions under ultrasound and computed tomography (CT) scanning, without any history of liver diseases or drug usage traced back. DIAGNOSES: Liver biopsy and laparoscopy were processed, and the lesions were eventually diagnosed as PH by histopathology, which microscopically presented with multiple sinusoidal dilatations with blood-filled cystic spaces. INTERVENTIONS: After the liver biopsy or laparoscopy, the patients were discharged and followed up in the clinic. OUTCOMES: Both patients were followed up for at least 1 year with good recovery. LESSONS: PH should always be recognized in the differentiation of liver lesions, particularly indistinctive lesion(s) without any history of liver-related diseases.

Connective tissue growth factor differentially binds to members of the cystine knot superfamily and potentiates platelet-derived growth factor-B signaling in rabbit corneal fibroblast cells.

AIM: To study the binding of connective tissue growth factor (CTGF) to cystine knot-containing ligands and how this impacts platelet-derived growth factor (PDGF)-B signaling. METHODS: The binding strengths of CTGF to cystine knot-containing growth factors including vascular endothelial growth factor (VEGF)-A, PDGF-B, bone morphogenetic protein (BMP)-4, and transforming growth factor (TGF)-ß1 were compared using the LexA-based yeast two-hybrid system. EYG48 reporter strain that carried a wild-type LEU2 gene under the control of LexA operators and a lacZ reporter plasmid (p80p-lacZ) containing eight high affinity LexA binding sites were used in the yeast two-hybrid analysis. Interactions between CTGF and the tested growth factors were evaluated based on growth of transformed yeast cells on selective media and colorimetric detection in a liquid ß-galactosidase activity assay. Dissociation constants of CTGF to VEGF-A isoform 165 or PDGF-BB homo-dimer were measured in surface plasma resonance (SPR) analysis. CTGF regulation in PDGF-B presentation to the PDGF receptor ß (PDGFRß) was also quantitatively assessed by the SPR analysis. Combinational effects of CTGF protein and PDGF-BB on activation of PDGFRß and downstream signaling molecules ERK1/2 and AKT were assessed in rabbit corneal fibroblast cells by Western analysis. RESULTS: In the LexA-based yeast two-hybrid system, cystine knot motifs of tested growth factors were fused to the activation domain of the transcriptional factor GAL4 while CTGF was fused to the DNA binding domain of the bacterial repressor protein LexA. Yeast co-transformants containing corresponding fusion proteins for CTGF and all four tested cystine knot motifs survived on selective medium containing galactose and raffinose but lacking histidine, tryptophan, and uracil. In liquid ß-galactosidase assays, CTGF expressing cells that were co-transformed with the cystine knot of VEGF-A had the highest activity, at 29.88 ± 0.91 fold above controls (P < 0.01). Cells containing the cystine knot of BMP-4 expressed the second most activity, with a 24.77 ± 0.47 fold increase (P < 0.01). Cells that contained the cystine knot of TGF-ß1 had a 3.80 ± 0.66 fold increase (P < 0.05) and the ones with the cystine knot of PDGF-B had a 2.64 ± 0.33 fold increase of ß-galactosidase activity (P < 0.01). Further SPR analysis showed that the association rate between VEGF-A 165 and CTGF was faster than PDGF-BB and CTGF. The calculated dissociation constant (KD) of CTGF to VEGF165 and PDGF-BB was 1.8 and 43 nmol/L respectively. PDGF-BB ligand and PDGFRß receptor formed a stable complex with a low dissociation constant 1.4 nmol/L. Increasing the concentration of CTGF up to 263.2 nmol/L significantly the ligand/receptor binding. In addition, CTGF potentiated phosphorylation of PDGFRß and AKT in rabbit corneal fibroblast cells stimulated by PDGF-BB in tissue culture condition. In contrast, CTGF did not affect PDGF-B induced phosphorylation of ERK1/2. CONCLUSION: CTGF has a differential binding affinity to VEGF-A, PDGF-B, BMP-4, and TGF-ß. Its weak association with PDGF-B may represent a novel mechanism to enhance PDGF-B signaling.

Oxidation and phosphorylation of MAP kinase 4 cause protein aggregation.

Mitogen-activated protein kinase (MPK) cascades are highly conserved signaling pathways that respond to environmental cues. Arabidopsis MPK4 has been identified as a stress-responsive protein kinase. Here we demonstrate that Brassica napus MPK4 (BnMPK4) is activated by hydrogen peroxide (H2O2) and phytohormone abscisic acid (ABA). Transient expression of a constitutively active BnMPK4 causes H2O2 production and cell death in Nicotiana benthamiana leaves. However, little is known about how H2O2 contributes to the regulation of MPK4 kinase function. Biochemical analysis revealed that recombinant BnMPK4 autophosphorylates on both threonine and tyrosine residues in the activation loop. In the presence of H2O2, phosphorylation of BnMPK4 caused protein aggregation in vitro. The aggregation of BnMPK4 could be reversed to the monomeric form by reducing reagents. Point-mutation of cysteine codons indicated that cysteine 232 is involved in protein aggregation. Our results suggest that BnMPK4 is involved in reactive oxygen species (ROS) signaling and metabolism, and its aggregation may be modulated by redox.

Thiol-based redox proteins in abscisic acid and methyl jasmonate signaling in Brassica napus guard cells.

Reversibly oxidized cysteine sulfhydryl groups serve as redox sensors or targets of redox sensing that are important in various physiological processes. However, little is known about redox-sensitive proteins in guard cells and how they function in stomatal signaling. In this study, Brassica napus guard-cell proteins altered by redox in response to abscisic acid (ABA) or methyl jasmonate (MeJA) were identified by complementary proteomics approaches, saturation differential in-gel electrophoresis and isotope-coded affinity tagging. In total, 65 and 118 potential redox-responsive proteins were identified in ABA- and MeJA-treated guard cells, respectively. All the proteins contain at least one cysteine, and over half of them are predicted to form intra-molecular disulfide bonds. Most of the proteins fall into the functional groups of 'energy', 'stress and defense' and 'metabolism'. Based on the peptide sequences identified by mass spectrometry, 30 proteins were common to ABA- and MeJA-treated samples. A total of 44 cysteines were mapped in the identified proteins, and their levels of redox sensitivity were quantified. Two of the proteins, a sucrose non-fermenting 1-related protein kinase and an isopropylmalate dehydrogenase, were confirmed to be redox-regulated and involved in stomatal movement. This study creates an inventory of potential redox switches, and highlights a protein redox regulatory mechanism in ABA and MeJA signal transduction in guard cells.

Members of the XB3 family from diverse plant species induce programmed cell death in Nicotiana benthamiana.

Programmed cell death has been associated with plant immunity and senescence. The receptor kinase XA21 confers resistance to bacterial blight disease of rice (Oryza sativa) caused by Xanthomonas oryzae pv. oryzae (Xoo). Here we show that the XA21 binding protein 3 (XB3) is capable of inducing cell death when overexpressed in Nicotiana benthamiana. XB3 is a RING finger-containing E3 ubiquitin ligase that has been positively implicated in XA21-mediated resistance. Mutation abolishing the XB3 E3 activity also eliminates its ability to induce cell death. Phylogenetic analysis of XB3-related sequences suggests a family of proteins (XB3 family) with members from diverse plant species. We further demonstrate that members of the XB3 family from rice, Arabidopsis and citrus all trigger a similar cell death response in Nicotiana benthamiana, suggesting an evolutionarily conserved role for these proteins in regulating programmed cell death in the plant kingdom.