Understanding the experiences of mothers receiving perinatal palliative care: A qualitative study.

BACKGROUND: Despite the diagnosis of life-limiting foetal conditions, some mothers choose to continue their pregnancies. The experiences of these individuals are relatively unknown, making it difficult for perinatal palliative services to be targeted towards their needs. AIM: To examine maternal experiences in perinatal palliative care among those who choose to continue their pregnancies despite life-limiting foetal condition. DESIGN: Qualitative, retrospective study involving semi-structured interviews. Braun & Clarke's reflexive thematic analyses using a constructionist-interpretive approach were conducted. SETTING/PARTICIPANTS: A total of 15 adult women participants who decided to continue their pregnancies after learning of life-limiting foetal diagnoses were recruited from a Singaporean tertiary hospital. Interviews were conducted in-person or via video conferencing. RESULTS: Seven themes were synthesized from the data: (1) Internal upheaval - 'World turns upside down'; (2) Role of religion and spirituality in hope of miracles; (3) Support from family and close friends; (4) Navigating a fragmented healthcare system; (5) Value added by the perinatal palliative service; (6) Goodbye and grieving and (7) No regrets and other personal reflections. CONCLUSIONS: Continuing a pregnancy despite the diagnosis of a life-limiting foetal condition can be challenging for mothers. To better meet their needs during this difficult period, perinatal palliative care must be patient-centred, multidisciplinary and non-judgmental. Efforts must be made to streamline the healthcare delivery process.

Unraveling the Impact of Acetylation Patterns in Chitosan Oligomers on Cu2+ Ion Binding: Insights from DFT Calculations.

Chitosans are partially acetylated polymers of glucosamine, structurally characterized by their degree of polymerization as well as their fraction and pattern of acetylation. These parameters strongly influence the physico-chemical properties and biological activities of chitosans, but structure-function relationships are only poorly understood. As an example, we here investigated the influence of acetylation on chitosan-copper complexation using density functional theory. We investigated the electronic structures of completely deacetylated and partially acetylated chitosan oligomers and their copper-bound complexes. Frontier molecular orbital theory revealed bonding orbitals for electrophiles and antibonding orbitals for nucleophiles in fully deacetylated glucosamine oligomers, while partially acetylated oligomers displayed bonding orbitals for both electrophiles and nucleophiles. Our calculations showed that the presence of an acetylated subunit in a chitosan oligomer affects the structural and the electronic properties of the oligomer by generating new intramolecular interactions with the free amino group of neighboring deacetylated subunits, thereby influencing its polarity. Furthermore, the band gap energy calculated from the fully and partially deacetylated oligomers indicates that the mobility of electrons in partially acetylated chitosan oligomers is higher than in fully deacetylated oligomers. In addition, fully deacetylated oligomers form more stable complexes with higher bond dissociation energies with copper than partially acetylated ones. Interestingly, in partially acetylated oligomers, the strength of copper binding was found to be dependent on the pattern of acetylation. Our study provides first insight into the influence of patterns of acetylation on the electronic and ion binding properties of chitosans. Depending on the intended application, the obtained results can serve as a guide for the selection of the optimal chitosan for a specific purpose.

Synthetic homoserine lactone analogues as antagonists of bacterial quorum sensing.

Quorum sensing (QS) is a density-dependent form of cell-cell communication that triggers the functional coordination of cooperative behaviors such as the production of virulence factors and biofilm formation. Quorum quenching (QQ) refers to all processes involved in the disruption of QS and is regarded as a promising strategy for treating bacterial infections. Herein, four compounds with closely related chemical structures to homoserine γ-lactone were synthesized and fully characterized. The compounds are termed TGK-series compounds. These compounds were subsequently tested in their QS inhibition activity using an E. coli Top 10 QS biosensor strain, a GFP QS reporter, that probes the capacity of bacteria to detect their cognate autoinducer N-(3-oxohexanoyl)-homoserine lactone (3OC6HSL) substrate by means of a single intracellular protein LuxR. All TGK-series compounds were found to significantly inhibit the ability of bacteria to produce GFP but without exerting toxicity when applied at a concentration of 50 µM. In parallel, the interaction of TGK-series compounds with LuxR were studied by molecular docking simulations. These studies revealed that TGK-series compounds bound to the natural substrate N-(3-oxo-octanoyl)-l-homoserine lactone (OOHL) binding site and that the binding ability of the compounds with the TraR protein (a surrogate of LuxR) was even more favorable in comparison with the natural substrate. It was also uncovered that TGK-series compounds form stronger hydrophobic interactions with the TraR protein than 3OC6HSL does, thus providing a rationale for the enhancement of the QQ activity of the synthetic TGK-series compounds. This study will serve to guide future works aimed to design promising novel QS inhibitor candidates on a rational basis.

A unique case of Lemierre's syndrome status post blunt cervical trauma.

BACKGROUND: Lemierre's syndrome is a rare but potentially fatal condition. The course is characterized by acute tonsillopharyngitis, bacteremia, internal jugular vein thrombosis, and septic embolization. There have been some cases secondary to penetrating trauma to the neck. Literature review has yielded no cases secondary to blunt neck trauma in the absence of oropharyngeal injury. We aim to shed light on this unique cause of Lemierre's syndrome, so as to raise the index of suspicion for clinicians working up patients with blunt cervical trauma. METHODS: We present a case of a 25-year-old male restrained driver who presented with left neck and shoulder pain with a superficial abrasion to the left neck from the seatbelt who was discharged same day by the Emergency Room physicians. He returned to the Emergency Department two days later with abdominal pain. As a part of his repeat evaluation, a set of blood cultures were sent and was sent home that day. The patient was called back to the hospital one day later as preliminary blood cultures were positive for Gram positive cocci and Gram negative anaerobes. Computerized tomography scan of the neck revealed extensive occlusive left internal jugular vein thrombosis and fluid collections concerning for abscesses, concerning for septic thrombophlebitis. The patient continued to decompensate, developing severe sepsis complicated by disseminated intravascular coagulation. RESULTS: The patient underwent a left neck exploration with en bloc resection of the left internal jugular vein, drainage of abscesses deep to the sternocleidomastoid, and washout/debridement of necrotic tissue. Direct laryngoscopy at the time of surgery revealed no injury to the aerodigestive tract. Wound cultures were consistent with blood cultures and grew Fusobacterium necrophorum, Staphylococcus epidermidis, and Methicillin-resistant staphylococcus aureus. The patient underwent two subsequent operative wound explorations without any evidence of residual infection. The patient was discharged home on postoperative day 13 on a course of antibiotics and aspirin. CONCLUSION: This case illustrates the importance of diagnosis of Lemierre's syndrome after an unconventional inciting event (blunt cervical trauma) and appropriate treatment.

'Slipped Sandwich' Model for Chitin and Chitosan Perception in Arabidopsis.

Chitin, a linear polymer of N-acetyl-d-glucosamine, and chitosans, fully or partially deacetylated derivatives of chitin, are known to elicit defense reactions in higher plants. We compared the ability of chitin and chitosan oligomers and polymers (chitin oligomers with degree of polymerization [DP] 3 to 8; chitosan oligomers with degree of acetylation [DA] 0 to 35% and DP 3 to 15; chitosan polymers with DA 1 to 60% and DP approximately 1,300) to elicit an oxidative burst indicative of induced defense reactions in Arabidopsis thaliana seedlings. Fully deacetylated chitosans were not able to trigger a response; elicitor activity increased with increasing DA of chitosan polymers. Partially acetylated chitosan oligomers required a minimum DP of 6 and at least four N-acetyl groups to trigger a response. Invariably, elicitation of an oxidative burst required the presence of the chitin receptor AtCERK1. Our results as well as previously published studies on chitin and chitosan perception in plants are best explained by a new general model of LysM-containing receptor complexes in which two partners form a long but off-set chitin-binding groove and are, thus, dimerized by one chitin or chitosan molecule, sharing a central GlcNAc unit with which both LysM domains interact. To verify this model and to distinguish it from earlier models, we assayed elicitor and inhibitor activities of selected partially acetylated chitosan oligomers with fully defined structures. In contrast to the initial 'continuous groove', the original 'sandwich', or the current 'sliding mode' models for the chitin/chitosan receptor, the here-proposed 'slipped sandwich' model-which builds on these earlier models and represents a consensus combination of these-is in agreement with all experimental observations.

A specific amino acid residue in the catalytic site of dandelion polyphenol oxidases acts as 'selector' for substrate specificity.

KEY MESSAGE: Successful site-directed mutagenesis combined with in silico modeling and docking studies for the first time offers experimental proof of the role of the 'substrate selector' residue in plant polyphenol oxidases. The plant and fungi enzymes responsible for tissue browning are called polyphenol oxidases (PPOs). In plants, PPOs often occur as families of isoenzymes which are differentially expressed, but little is known about their physiological roles or natural substrates. In a recent study that explored these structure-function relationships, the eleven known dandelion (Taraxacum officinale) PPOs were shown to separate into two different phylogenetic groups differing in catalytic cavity architecture, kinetic parameters, and substrate range. The same study proposed that the PPOs' substrate specificity is controlled by one specific amino acid residue positioned at the entrance to the catalytic site: whereas group 1 dandelion PPOs possess a hydrophobic isoleucine (I) at position HB2+1, group 2 PPOs exhibit a larger, positively charged arginine (R). However, this suggestion was only based on bioinformatic analyses, not experiments. To experimentally investigate this hypothesis, we converted group 1 ToPPO-2 and group 2 ToPPO-6 into PPO-2-I244R and PPO-6-R254I, respectively, and expressed them in E. coli. By performing detailed kinetic characterization and in silico docking studies, we found that replacing this single amino acid significantly changed the PPO's substrate specificity. Our findings therefore proof the role of the 'substrate selector' in plant PPOs.

Cost of Medical Care of Patients with Advanced Serious Illness in Singapore (COMPASS): prospective cohort study protocol.

BACKGROUND: Advanced cancer significantly impacts quality of life of patients and families as they cope with symptom burden, treatment decision-making, uncertainty and costs of treatment. In Singapore, information about the experiences of advanced cancer patients and families and the financial cost they incur for end-of-life care is lacking. Understanding of this information is needed to inform practice and policy to ensure continuity and affordability of care at the end of life. The primary objectives of the Cost of Medical Care of Patients with Advanced Serious Illness in Singapore (COMPASS) cohort study are to describe changes in quality of life and to quantify healthcare utilization and costs of patients with advanced cancer at the end of life. Secondary objectives are to investigate patient and caregiver preferences for diagnostic and prognostic information, preferences for end-of-life care, caregiver burden and perceived quality of care and to explore how these change as illness progresses and finally to measure bereavement adjustment. The purpose of this paper is to present the COMPASS protocol in order to promote scientific transparency. METHODS: This cohort study recruits advanced cancer patients (n = 600) from outpatient medical oncology clinics at two public tertiary healthcare institutions in Singapore. Patients and their primary informal caregiver are surveyed every 3 months until patients' death; caregivers are followed until 6 months post patient death. Patient medical and billing records are obtained and merged with patient survey data. The treating medical oncologists of participating patients are surveyed to obtain their beliefs regarding care delivery for the patient. DISCUSSION: The study will allow combination of self-report, medical, and cost data from various sources to present a comprehensive picture of the end-of-life experience of advanced cancer patients in a unique Asian setting. This study is responsive to Singapore's National Strategy for Palliative Care which aims to identify opportunities to meet the growing need for high quality care for Singapore's aging population. Results will also be of interest to policy makers and researchers beyond Singapore who are interested to understand and improve the end-of-life experience of cancer patients. TRIAL REGISTRATION: NCT02850640 (Prospectively registered on June 9, 2016).

Protein-engineering of chitosanase from Bacillus sp. MN to alter its substrate specificity.

Partially acetylated chitosan oligosaccharides (paCOS) have various potential applications in agriculture, biomedicine, and pharmaceutics due to their suitable bioactivities. One method to produce paCOS is partial chemical hydrolysis of chitosan polymers, but that leads to poorly defined mixtures of oligosaccharides. However, the effective production of defined paCOS is crucial for fundamental research and for developing applications. A more promising approach is enzymatic depolymerization of chitosan using chitinases or chitosanases, as the substrate specificity of the enzyme determines the composition of the oligomeric products. Protein-engineering of these enzymes to alter their substrate specificity can overcome the limitations associated with naturally occurring enzymes and expand the spectrum of specific paCOS that can be produced. Here, engineering the substrate specificity of Bacillus sp. MN chitosanase is described for the first time. Two muteins with active site substitutions can accept N-acetyl-D-glucosamine units at their subsite (-2), which is impossible for the wildtype enzyme.

A Recombinant Fungal Chitin Deacetylase Produces Fully Defined Chitosan Oligomers with Novel Patterns of Acetylation.

Partially acetylated chitosan oligosaccharides (paCOS) are potent biologics with many potential applications, and their bioactivities are believed to be dependent on their structure, i.e., their degrees of polymerization and acetylation, as well as their pattern of acetylation. However, paCOS generated via chemical N-acetylation or de-N-acetylation of GlcN or GlcNAc oligomers, respectively, typically display random patterns of acetylation, making it difficult to control and predict their bioactivities. In contrast, paCOS produced from chitin deacetylases (CDAs) acting on chitin oligomer substrates may have specific patterns of acetylation, as shown for some bacterial CDAs. However, compared to what we know about bacterial CDAs, we know little about the ability of fungal CDAs to produce defined paCOS with known patterns of acetylation. Therefore, we optimized the expression of a chitin deacetylase from the fungus Puccinia graminis f. sp. tritici in Escherichia coli The best yield of functional enzyme was obtained as a fusion protein with the maltose-binding protein (MBP) secreted into the periplasmic space of the bacterial host. We characterized the MBP fusion protein from P. graminis (PgtCDA) and tested its activity on different chitinous substrates. Mass spectrometric sequencing of the products obtained by enzymatic deacetylation of chitin oligomers, i.e., tetramers to hexamers, revealed that PgtCDA generated paCOS with specific acetylation patterns of A-A-D-D, A-A-D-D-D, and A-A-D-D-D-D, respectively (A, GlcNAc; D, GlcN), indicating that PgtCDA cannot deacetylate the two GlcNAc units closest to the oligomer's nonreducing end. This unique property of PgtCDA significantly expands the so far very limited library of well-defined paCOS available to test their bioactivities for a wide variety of potential applications. IMPORTANCE: We successfully achieved heterologous expression of a fungal chitin deacetylase gene from the basidiomycete Puccinia graminis f. sp. tritici in the periplasm of E. coli as a fusion protein with the maltose-binding protein; this strategy allows the production of these difficult-to-express enzymes in sufficient quantities for them to be characterized and optimized through protein engineering. Here, the recombinant enzyme was used to produce partially acetylated chitosan oligosaccharides from chitin oligomers, whereby the pronounced regioselectivity of the enzyme led to the production of defined products with novel patterns of acetylation. This approach widens the scope for both the production and functional analysis of chitosan oligomers and thus will eventually allow the detailed molecular structure-function relationships of biologically active chitosans to be studied, which is essential for developing applications for these functional biopolymers for a circular bioeconomy, e.g., in agriculture, medicine, cosmetics, and food sciences.

Experimental and bioinformatic characterization of a recombinant polygalacturonase-inhibitor protein from pearl millet and its interaction with fungal polygalacturonases.

Polygalacturonases (PGs) are hydrolytic enzymes employed by several phytopathogens to weaken the plant cell wall by degrading homopolygalacturonan, a major constituent of pectin. Plants fight back by employing polygalacturonase-inhibitor proteins (PGIPs). The present study compared the inhibition potential of pearl millet PGIP (Pennisetum glaucum; PglPGIP1) with the known inhibition of Phaseolus vulgaris PGIP (PvPGIP2) against two PGs, the PG-II isoform from Aspergillus niger (AnPGII) and the PG-III isoform from Fusarium moniliforme (FmPGIII). The key rationale was to elucidate the relationship between the extent of sequence similarity of the PGIPs and the corresponding PG inhibition potential. First, a pearl millet pgip gene (Pglpgip1) was isolated and phylogenetically placed among monocot PGIPs alongside foxtail millet (Setaria italica). Upstream sequence analysis of Pglpgip1 identified important cis-elements responsive to light, plant stress hormones, and anoxic stress. PglPGIP1, heterologously produced in Escherichia coli, partially inhibited AnPGII non-competitively with a pH optimum between 4.0 and 4.5, and showed no inhibition against FmPGIII. Docking analysis showed that the concave surface of PglPGIP1 interacted strongly with the N-terminal region of AnPGII away from the active site, whereas it weakly interacted with the C-terminus of FmPGIII. Interestingly, PglPGIP1 and PvPGIP2 employed similar motif regions with few identical amino acids for interaction with AnPGII at non-substrate-binding sites; however, they engaged different regions of AnPGII. Computational mutagenesis predicted D126 (PglPGIP1)-K39 (AnPGII) to be the most significant binding contact in the PglPGIP1-AnPGII complex. Such protein-protein interaction studies are crucial in the future generation of designer host proteins for improved resistance against ever-evolving pathogen virulence factors.

Chemogenomics of pyridoxal 5'-phosphate dependent enzymes.

Pyridoxal 5'-phosphate (PLP) dependent enzymes comprise a large family that plays key roles in amino acid metabolism and are acquiring an increasing interest as drug targets. For the identification of compounds inhibiting PLP-dependent enzymes, a chemogenomics-based approach has been adopted in this work. Chemogenomics exploits the information coded in sequences and three-dimensional structures to define pharmacophore models. The analysis was carried out on a dataset of 65 high-resolution PLP-dependent enzyme structures, including representative members of four-fold types. Evolutionarily conserved residues relevant to coenzyme or substrate binding were identified on the basis of sequence-structure comparisons. A dataset was obtained containing the information on conserved residues at substrate and coenzyme binding site for each representative PLP-dependent enzyme. By linking coenzyme and substrate pharmacophores, bifunctional pharmacophores were generated that will constitute the basis for future development of small inhibitors targeting specific PLP-dependent enzymes.

Guillain Barre Syndrome after vaccination against Corona Virus Disease19: Managed in limited resource setting.

A 16-year-old boy who classically featured Guillain Barre Syndrome (GBS) after Corona Virus Disease-19 vaccination was timely treated successfully in limited resource setting in far western province. After Moderna (mRNA COVID 19 Vaccine) vaccination, he rapidly developed ascending paralysis of limbs without autonomic and sensory or cranial nerve involvement. He has been treated with Intravenous Immuno-Globulin (IVIG). Over six-weeks long observation and supportive care and he was discharged with full recovery. Many GBS cases after vaccination have been reported but yet to know the association of vaccine. It is very important to address the complication for successful vaccination programme. Keywords: Complication; COVID-19; guillain barre syndrome; vaccine.

The multifaceted pyridoxal 5'-phosphate-dependent O-acetylserine sulfhydrylase.

Cysteine is the final product of the reductive sulfate assimilation pathway in bacteria and plants and serves as the precursor for all sulfur-containing biological compounds, such as methionine, S-adenosyl methionine, iron-sulfur clusters and glutathione. Moreover, in several microorganisms cysteine plays a role as a reducing agent, eventually counteracting host oxidative defense strategies. Cysteine is synthesized by the PLP-dependent O-acetylserine sulfhydrylase, a dimeric enzyme belonging to the fold type II, catalyzing a beta-replacement reaction. In this review, the spectroscopic properties, catalytic mechanism, three-dimensional structure, conformational changes accompanying catalysis, determinants of enzyme stability, role of selected amino acids in catalysis, and the regulation of enzyme activity by ligands and interaction with serine acetyltransferase, the preceding enzyme in the biosynthetic pathway, are described. Given the key biological role played by O-acetylserine sulfhydrylase in bacteria, inhibitors with potential antibiotic activity have been developed. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.

Identifying Core Domains to Assess the "Quality of Death": A Scoping Review.

CONTEXT: There is growing recognition of the value to patients, families, society, and health systems in providing healthcare, including end-of-life care, that is consistent with both patient preferences and clinical guidelines. OBJECTIVES: Identify the core domains and subdomains that can be used to evaluate the performance of end-of-life care within and across health systems. METHODS: PubMed/MEDLINE (NCBI), PsycINFO (ProQuest), and CINAHL (EBSCO) databases were searched for peer-reviewed journal articles published prior to February 22, 2020. The SPIDER tool was used to determine search terms. A priori criteria were followed with independent review to identify relevant articles. RESULTS: A total of 309 eligible articles were identified out of 2728 discrete results. The articles represent perspectives from the broader health system (11), patients (70), family and informal caregivers (65), healthcare professionals (43), multiple viewpoints (110), and others (10). The most common condition of focus was cancer (103) and the majority (245) of the studies concentrated on high-income country contexts. The review identified five domains and 11 subdomains focused on structural factors relevant to end-of-life care at the broader health system level, and two domains and 22 subdomains focused on experiential aspects of end-of-life care from the patient and family perspectives. The structural health system domains were: 1) stewardship and governance, 2) resource generation, 3) financing and financial protection, 4) service provision, and 5) access to care. The experiential domains were: 1) quality of care, and 2) quality of communication. CONCLUSION: The review affirms the need for a people-centered approach to managing the delicate process and period of accepting and preparing for the end of life. The identified structural and experiential factors pertinent to the "quality of death" will prove invaluable for future efforts aimed to quantify health system performance in the end-of-life period.

Cross Country Comparison of Expert Assessments of the Quality of Death and Dying 2021.

CONTEXT: Few efforts have attempted to quantify how well countries deliver end-of-life (EOL) care. OBJECTIVES: To score, grade, and rank countries (and Hong Kong and Taiwan) on the quality of EOL care based on assessments from country experts using a novel preference-based scoring algorithm. METHODS: We fielded a survey to country experts around the world, asking them to assess the performance of their country on 13 key indicators of EOL care. Results were combined with preference weights from caregiver-proxies of recently deceased patients to generate a preference-weighted summary score. The scores were then converted to grades (from A-F) and a ranking was created for all included countries. RESULTS: The final sample included responses from 181 experts representing 81 countries with 2 or more experts reporting. The 6 countries who received the highest assessment scores and a grade of A were United Kingdom, Ireland, Taiwan, Australia, Republic of Korea, and Costa Rica. Only Costa Rica (upper middle) is not a high income country. Not until Uganda (ranked 31st) does a low-income country appear on the ranking. Based on the assessment scores, twenty-one countries received a failing grade, with only two - Czech Republic (66th), and Portugal (75th) - being high income countries. CONCLUSION: This study provides an example of how a preference-based scoring algorithm and input from key stakeholders can be used to assess EOL health system performance. Results highlight the large disparities in assessments of the quality of EOL care across countries, and especially between the highest income countries and others.

Customized chitooligosaccharide production-controlling their length via engineering of rhizobial chitin synthases and the choice of expression system.

Chitooligosaccharides (COS) have attracted attention from industry and academia in various fields due to their diverse bioactivities. However, their conventional chemical production is environmentally unfriendly and in addition, defined and pure molecules are both scarce and expensive. A promising alternative is the in vivo synthesis of desired COS in microbial platforms with specific chitin synthases enabling a more sustainable production. Hence, we examined the whole cell factory approach with two well-established microorganisms-Escherichia coli and Corynebacterium glutamicum-to produce defined COS with the chitin synthase NodC from Rhizobium sp. GRH2. Moreover, based on an in silico model of the synthase, two amino acids potentially relevant for COS length were identified and mutated to direct the production. Experimental validation showed the influence of the expression system, the mutations, and their combination on COS length, steering the production from originally pentamers towards tetramers or hexamers, the latter virtually pure. Possible explanations are given by molecular dynamics simulations. These findings pave the way for a better understanding of chitin synthases, thus allowing a more targeted production of defined COS. This will, in turn, at first allow better research of COS' bioactivities, and subsequently enable sustainable large-scale production of oligomers.

Proteomic Analysis of S-Nitrosation Sites During Somatic Embryogenesis in Brazilian Pine, Araucaria angustifolia (Bertol.) Kuntze.

Cysteine S-nitrosation is a redox-based post-translational modification that mediates nitric oxide (NO) regulation of various aspects of plant growth, development and stress responses. Despite its importance, studies exploring protein signaling pathways that are regulated by S-nitrosation during somatic embryogenesis have not been performed. In the present study, endogenous cysteine S-nitrosation site and S-nitrosated proteins were identified by iodo-TMT labeling during somatic embryogenesis in Brazilian pine, an endangered native conifer of South America. In addition, endogenous -S-nitrosothiol (SNO) levels and S-nitrosoglutathione reductase (GSNOR) activity were determined in cell lines with contrasting embryogenic potential. Overall, we identified an array of proteins associated with a large variety of biological processes and molecular functions with some of them already described as important for somatic embryogenesis (Class IV chitinase, pyruvate dehydrogenase E1 and dehydroascorbate reductase). In total, our S-nitrosoproteome analyses identified 18 endogenously S-nitrosated proteins and 50 in vitro S-nitrosated proteins (after GSNO treatment) during cell culture proliferation and embryo development. Furthermore, SNO levels and GSNOR activity were increased during embryo formation. These findings expand our understanding of the Brazilian pine proteome and shed novel insights into the potential use of pharmacological manipulation of NO levels by using NO inhibitors and donors during somatic embryogenesis.

Chitosan and Chitin Deacetylase Activity Are Necessary for Development and Virulence of Ustilago maydis.

The biotrophic fungus Ustilago maydis harbors a chitin deacetylase (CDA) family of six active genes as well as one pseudogene which are differentially expressed during colonization. This includes one secreted soluble CDA (Cda4) and five putatively glycosylphosphatidylinositol (GPI)-anchored CDAs, of which Cda7 belongs to a new class of fungal CDAs. Here, we provide a comprehensive functional study of the entire family. While budding cells of U. maydis showed a discrete pattern of chitosan staining, biotrophic hyphae appeared surrounded by a chitosan layer. We purified all six active CDAs and show their activity on different chitin substrates. Single as well as multiple cda mutants were generated and revealed a virulence defect for mutants lacking cda7 We implicated cda4 in production of the chitosan layer surrounding biotrophic hyphae and demonstrated that the loss of this layer does not reduce virulence. By combining different cda mutations, we detected redundancy as well as specific functions for certain CDAs. Specifically, certain combinations of mutations significantly affected virulence concomitantly with reduced adherence, appressorium formation, penetration, and activation of plant defenses. Attempts to inactivate all seven cda genes simultaneously were unsuccessful, and induced depletion of cda2 in a background lacking the other six cda genes illustrated an essential role of chitosan for cell wall integrity.IMPORTANCE The basidiomycete Ustilago maydis causes smut disease in maize, causing substantial losses in world corn production. This nonobligate pathogen penetrates the plant cell wall with the help of appressoria and then establishes an extensive biotrophic interaction, where the hyphae are tightly encased by the plant plasma membrane. For successful invasion and development in plant tissue, recognition of conserved fungal cell wall components such as chitin by the plant immune system needs to be avoided or suppressed. One strategy to achieve this lies in the modification of chitin to chitosan by chitin deacetylases (CDAs). U. maydis has seven cda genes. This study reveals discrete as well as redundant contributions of these genes to virulence as well as to cell wall integrity. Unexpectedly, the inactivation of all seven genes is not tolerated, revealing an essential role of chitosan for viability.

Transcriptome Analysis of Solanum Tuberosum Genotype RH89-039-16 in Response to Chitosan.

Potato (Solanum tuberosum L.) is the worldwide most important nongrain crop after wheat, rice, and maize. The autotetraploidy of the modern commercial potato makes breeding of new resistant and high-yielding cultivars challenging due to complicated and time-consuming identification and selection processes of desired crop features. On the other hand, plant protection of existing cultivars using conventional synthetic pesticides is increasingly restricted due to safety issues for both consumers and the environment. Chitosan is known to display antimicrobial activity against a broad range of plant pathogens and shows the ability to trigger resistance in plants by elicitation of defense responses. As chitosan is a renewable, biodegradable and nontoxic compound, it is considered as a promising next-generation plant-protecting agent. However, the molecular and cellular modes of action of chitosan treatment are not yet understood. In this study, transcriptional changes in chitosan-treated potato leaves were investigated via RNA sequencing. Leaves treated with a well-defined chitosan polymer at low concentration were harvested 2 and 5 h after treatment and their expression profile was compared against water-treated control plants. We observed 32 differentially expressed genes (fold change ≥ 1; p-value ≤ 0.05) 2 h after treatment and 83 differentially expressed genes 5 h after treatment. Enrichment analysis mainly revealed gene modulation associated with electron transfer chains in chloroplasts and mitochondria, accompanied by the upregulation of only a very limited number of genes directly related to defense. As chitosan positively influences plant growth, yield, and resistance, we conclude that activation of electron transfer might result in the crosstalk of different organelles via redox signals to activate immune responses in preparation for pathogen attack, concomitantly resulting in a generally improved metabolic state, fostering plant growth and development. This conclusion is supported by the rapid and transient production of reactive oxygen species in a typical oxidative burst in the potato leaves upon chitosan treatment. This study furthers our knowledge on the mode of action of chitosan as a plant-protecting agent, as a prerequisite for improving its ability to replace or reduce the use of less environmentally friendly agro-chemicals.

Screening of Bacterial Quorum Sensing Inhibitors in a Vibrio fischeri LuxR-Based Synthetic Fluorescent E. coli Biosensor.

A library of 23 pure compounds of varying structural and chemical characteristics was screened for their quorum sensing (QS) inhibition activity using a synthetic fluorescent Escherichia coli biosensor that incorporates a modified version of lux regulon of Vibrio fischeri. Four such compounds exhibited QS inhibition activity without compromising bacterial growth, namely, phenazine carboxylic acid (PCA), 2-heptyl-3-hydroxy-4-quinolone (PQS), 1H-2-methyl-4-quinolone (MOQ) and genipin. When applied at 50 µM, these compounds reduced the QS response of the biosensor to 33.7% ± 2.6%, 43.1% ± 2.7%, 62.2% ± 6.3% and 43.3% ± 1.2%, respectively. A series of compounds only showed activity when tested at higher concentrations. This was the case of caffeine, which, when applied at 1 mM, reduced the QS to 47% ± 4.2%. In turn, capsaicin, caffeic acid phenethyl ester (CAPE), furanone and polygodial exhibited antibacterial activity when applied at 1mM, and reduced the bacterial growth by 12.8% ± 10.1%, 24.4% ± 7.0%, 91.4% ± 7.4% and 97.5% ± 3.8%, respectively. Similarly, we confirmed that trans-cinnamaldehyde and vanillin, when tested at 1 mM, reduced the QS response to 68.3% ± 4.9% and 27.1% ± 7.4%, respectively, though at the expense of concomitantly reducing cell growth by 18.6% ± 2.5% and 16% ± 2.2%, respectively. Two QS natural compounds of Pseudomonas aeruginosa, namely PQS and PCA, and the related, synthetic compounds MOQ, 1H-3-hydroxyl-4-quinolone (HOQ) and 1H-2-methyl-3-hydroxyl-4-quinolone (MHOQ) were used in molecular docking studies with the binding domain of the QS receptor TraR as a target. We offer here a general interpretation of structure-function relationships in this class of compounds that underpins their potential application as alternatives to antibiotics in controlling bacterial virulence.