Bound on 3+1 Active-Sterile Neutrino Mixing from the First Four-Week Science Run of KATRIN

We report on the light sterile neutrino search from the first four-week science run of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are analyzed by a high-resolution MAC-E filter down to 40 eV below the endpoint at 18.57 keV. We consider the framework with three active neutrinos and one sterile neutrino. The analysis is sensitive to the mass, m_{4}, of the fourth mass state for m_{4}^{2}≲1000  eV^{2} and to active-to-sterile neutrino mixing down to |U_{e4}|^{2}≳2×10^{-2}. No significant spectral distortion is observed and exclusion bounds on the sterile mass and mixing are reported. These new limits supersede the Mainz results for m_{4}^{2}≲1000  eV^{2} and improve the Troitsk bound for m_{4}^{2}<30  eV^{2}. The reactor and gallium anomalies are constrained for 100<Δm_{41}^{2}<1000  eV^{2}.

Processing and Formation of Bioactive CLE40 Peptide Are Controlled by Posttranslational Proline Hydroxylation

Small posttranslationally modified signaling peptides are proteolytically derived from larger precursor proteins and subject to several additional steps of modification, including Pro hydroxylation, Hyp glycosylation, and/or Tyr sulfation. The processing proteases and the relevance of posttranslational modifications for peptide biogenesis and activity are largely unknown. In this study these questions were addressed for the Clavata3/Endosperm Surrounding Region (CLE) peptide CLE40, a peptide regulator of stem cell differentiation in the Arabidopsis (Arabidopsis thaliana) root meristem. We identify three subtilases (SBT1.4, SBT1.7, and SBT4.13) that cleave the CLE40 precursor redundantly at two sites. C-terminal processing releases the mature peptide from its precursor and is thus required for signal biogenesis. SBT-mediated cleavage at a second site within the mature peptide attenuates the signal. The second cleavage is prevented by Pro hydroxylation, resulting in the formation of mature and bioactive CLE40 in planta. Our data reveal a role for posttranslational modification by Pro hydroxylation in the regulation of CLE40 formation and activity.

The biogenesis of CLEL peptides involves several processing events in consecutive compartments of the secretory pathway

Post-translationally modified peptides are involved in many aspects of plant growth and development. The maturation of these peptides from their larger precursors is still poorly understood. We show here that the biogenesis of CLEL6 and CLEL9 peptides in Arabidopsis thaliana requires a series of processing events in consecutive compartments of the secretory pathway. Following cleavage of the signal peptide upon entry into the endoplasmic reticulum (ER), the peptide precursors are processed in the cis-Golgi by the subtilase SBT6.1. SBT6.1-mediated cleavage within the variable domain allows for continued passage of the partially processed precursors through the secretory pathway, and for subsequent post-translational modifications including tyrosine sulfation and proline hydroxylation within, and proteolytic maturation after exit from the Golgi. Activation by subtilases including SBT3.8 in post-Golgi compartments depends on the N-terminal aspartate of the mature peptides. Our work highlights the complexity of post-translational precursor maturation allowing for stringent control of peptide biogenesis.

Peptide signaling for drought-induced tomato flower drop

The premature abscission of flowers and fruits limits crop yield under environmental stress. Drought-induced flower drop in tomato plants was found to be regulated by phytosulfokine (PSK), a peptide hormone previously known for its growth-promoting and immune-modulating activities. PSK formation in response to drought stress depends on phytaspase 2, a subtilisin-like protease of the phytaspase subtype that generates the peptide hormone by aspartate-specific processing of the PSK precursor in the tomato flower pedicel. The mature peptide acts in the abscission zone where it induces expression of cell wall hydrolases that execute the abscission process. Our results provide insight into the molecular control of abscission as regulated by proteolytic processing to generate a small plant peptide hormone.

A two-way molecular dialogue between embryo and endosperm is required for seed development

The plant embryonic cuticle is a hydrophobic barrier deposited de novo by the embryo during seed development. At germination, it protects the seedling from water loss and is, thus, critical for survival. Embryonic cuticle formation is controlled by a signaling pathway involving the ABNORMAL LEAF SHAPE1 subtilase and the two GASSHO receptor-like kinases. We show that a sulfated peptide, TWISTED SEED1 (TWS1), acts as a GASSHO ligand. Cuticle surveillance depends on the action of the subtilase, which, unlike the TWS1 precursor and the GASSHO receptors, is not produced in the embryo but in the neighboring endosperm. Subtilase-mediated processing of the embryo-derived TWS1 precursor releases the active peptide, triggering GASSHO-dependent cuticle reinforcement in the embryo. Thus, a bidirectional molecular dialogue between embryo and endosperm safeguards cuticle integrity before germination.

The Systemin Signaling Cascade As Derived from Time Course Analyses of the Systemin-responsive Phosphoproteome

Systemin is a small peptide with important functions in plant wound response signaling. Although the transcriptional responses of systemin action are well described, the signaling cascades involved in systemin perception and signal transduction at the protein level are poorly understood. Here we used a tomato cell suspension culture system to profile phosphoproteomic responses induced by systemin and its inactive Thr17Ala analog, allowing us to reconstruct a systemin-specific kinase/phosphatase signaling network. Our time-course analysis revealed early phosphorylation events at the plasma membrane, such as dephosphorylation of H+-ATPase, rapid phosphorylation of NADPH-oxidase and Ca2+-ATPase. Later responses involved transient phosphorylation of small GTPases, vesicle trafficking proteins and transcription factors. Based on a correlation analysis of systemin-induced phosphorylation profiles, we predicted substrate candidates for 44 early systemin-responsive kinases, which includes receptor kinases and downstream kinases such as MAP kinases, as well as nine phosphatases. We propose a regulatory module in which H+-ATPase LHA1 is rapidly de-phosphorylated at its C-terminal regulatory residue T955 by phosphatase PLL5, resulting in the alkalization of the growth medium within 2 mins of systemin treatment. We found the MAP kinase MPK2 to have increased phosphorylation level at its activating TEY-motif at 15 min post-treatment. The predicted interaction of MPK2 with LHA1 was confirmed by in vitro kinase assays, suggesting that the H+-ATPase LHA1 is re-activated by MPK2 later in the systemin response. Our data set provides a resource of proteomic events involved in systemin signaling that will be valuable for further in-depth functional studies in elucidation of systemin signaling cascades.

[Allergic respiratory diseases related to mould in the home]

Exposure to mould is a potential risk factor for asthma in both adults and children. In adult, the relation between exposure, sensitization and symptoms has been demonstrated in severe asthmatics sensitized to Alternaria. For children, exposure to mould in childhood is a risk factor for asthma in both atopic and non-atopic individuals. Exposure or sensitization to moulds are a risk factor for severe asthma and/or exacerbations in children. There appears to be a causal relationship between exposure and asthma. This link seems less significant in adults. However, in adults mould sensitive asthma seems to determine a phenotype of severe asthma associated with more marked obstructive lung disease. Moulds can stimulate either innate or the acquired immunity. They are responsible for a marked Th2 inflammation leading to more severe asthma. Besides the immunological mechanisms, toxic mechanisms can also intervene. It is therefore not correct to reduce the effect of moulds, particularly in respiratory symptoms, to only allergic mechanisms.

Multiple clinical profiles of families with the short QT syndrome

Aims

Short QT syndrome (SQTS) is a rare cardiac channelopathy characterized by a shortened corrected QT (QTc)-interval that can lead to ventricular arrhythmias and sudden cardiac death. The aim of this study was to investigate the clinical phenotypes and long-term outcomes of three families harbouring genetic mutations associated with the SQTS.

Methods and results

Clinical data included medical history, physical examination, 12-lead ECG, 24-h Holter-ECG, and transthoracic echocardiography from three index patients and their first-degree relatives. Next generation clinical exome sequencing and genetic cascade screening were performed in index patients and their relatives, respectively. Two index patients experienced malignant ventricular arrhythmias and one patient suffered from arrhythmogenic syncope during a median follow-up period of 8 years. They all had genetic mutations associated with the SQTS. Two mutations were found in the KCNH2 gene, and one in the CACNA2D gene. One patient had an additional SCN10A variant. Alive and mutation-positive family members had short QTc-intervals, but no further phenotypic manifestations. None of the mutation-negative family members had an abnormal ECG or any symptoms. In all patients with shortened QTc-intervals, the QTc-interval had a low long-term variability and QTc shortening always remained detectable by 12-lead ECG.

Conclusion

This study shows the variety of phenotypic manifestations in different families with SQTS. It further emphasizes the importance of a 12-lead ECG for early diagnosis, and the utility of next generation sequencing for the identification of mutations associated with the SQTS.

Regulation of plant peptide hormones and growth factors by post-translational modification

The number, diversity and significance of peptides as regulators of cellular differentiation, growth, development and defence of plants has long been underestimated. Peptides have now emerged as an important class of signals for cell-to-cell communication over short distances, and also for long-range signalling. We refer to these signalling molecules as peptide growth factors and peptide hormones, respectively. As compared to remarkable progress with respect to the mechanisms of peptide perception and signal transduction, the biogenesis of signalling peptides is still in its infancy. This review focuses on the biogenesis and activity of small post-translationally modified peptides. These peptides are derived from inactive pre-pro-peptides of approximately 70-120 amino acids. Multiple post-translational modifications (PTMs) may be required for peptide maturation and activation, including proteolytic processing, tyrosine sulfation, proline hydroxylation and hydroxyproline glycosylation. While many of the enzymes responsible for these modifications have been identified, their impact on peptide activity and signalling is not fully understood. These PTMs may or may not be required for bioactivity, they may inactivate the peptide or modify its signalling specificity, they may affect peptide stability or targeting, or its binding affinity with the receptor. In the present review, we will first introduce the peptides that undergo PTMs and for which these PTMs were shown to be functionally relevant. We will then discuss the different types of PTMs and the impact they have on peptide activity and plant growth and development. We conclude with an outlook on the open questions that need to be addressed in future research.

The tomato subtilase family includes several cell death-related proteinases with caspase specificity

Phytaspases are Asp-specific subtilisin-like plant proteases that have been likened to animal caspases with respect to their regulatory function in programmed cell death (PCD). We identified twelve putative phytaspase genes in tomato that differed widely in expression level and tissue-specific expression patterns. Most phytaspase genes are tandemly arranged on tomato chromosomes one, four, and eight, and many belong to taxon-specific clades, e.g. the P69 clade in the nightshade family, suggesting that these genes evolved by gene duplication after speciation. Five tomato phytaspases (SlPhyts) were expressed in N. benthamiana and purified to homogeneity. Substrate specificity was analyzed in a proteomics assay and with a panel of fluorogenic peptide substrates. Similar to animal caspases, SlPhyts recognized an extended sequence motif including Asp at the cleavage site. Clear differences in cleavage site preference were observed implying different substrates in vivo and, consequently, different physiological functions. A caspase-like function in PCD was confirmed for five of the seven tested phytaspases. Cell death was triggered by ectopic expression of SlPhyts 2, 3, 4, 5, 6 in tomato leaves by agro-infiltration, as well as in stably transformed transgenic tomato plants. SlPhyts 3, 4, and 5 were found to contribute to cell death under oxidative stress conditions.

From structure to function - a family portrait of plant subtilases

Contents Summary 901 I. Introduction 901 II. Biochemistry and structure of plant SBTs 902 III. Phylogeny of plant SBTs and family organization 903 IV. Physiological roles of plant SBTs 905 V. Conclusions and outlook 911 Acknowledgements 912 References 912 SUMMARY: Subtilases (SBTs) are serine peptidases that are found in all three domains of life. As compared with homologs in other Eucarya, plant SBTs are more closely related to archaeal and bacterial SBTs, with which they share many biochemical and structural features. However, in the course of evolution, functional diversification led to the acquisition of novel, plant-specific functions, resulting in the present-day complexity of the plant SBT family. SBTs are much more numerous in plants than in any other organism, and include enzymes involved in general proteolysis as well as highly specific processing proteases. Most SBTs are targeted to the cell wall, where they contribute to the control of growth and development by regulating the properties of the cell wall and the activity of extracellular signaling molecules. Plant SBTs affect all stages of the life cycle as they contribute to embryogenesis, seed development and germination, cuticle formation and epidermal patterning, vascular development, programmed cell death, organ abscission, senescence, and plant responses to their biotic and abiotic environments. In this article we provide a comprehensive picture of SBT structure and function in plants.

Phytaspase-mediated precursor processing and maturation of the wound hormone systemin

Peptide hormones are implicated in many important aspects of plant life and are usually synthesized as precursor proteins. In contrast to animals, data for plant peptide hormone maturation are scarce and the specificity of processing enzyme(s) is largely unknown. Here we tested a hypothesis that processing of prosystemin, a precursor of tomato (Solanum lycopersicum) wound hormone systemin, is performed by phytaspases, aspartate-specific proteases of the subtilase family. Following the purification of phytaspase from tomato leaves, two tomato phytaspase genes were identified, the cDNAs were cloned and the recombinant enzymes were obtained after transient expression in Nicotiana benthamiana. The newly identified tomato phytaspases hydrolyzed prosystemin at two aspartate residues flanking the systemin sequence. Site-directed mutagenesis of the phytaspase cleavage sites in prosystemin abrogated not only the phytaspase-mediated processing of the prohormone in vitro, but also the ability of prosystemin to trigger the systemic wound response in vivo. The data show that the prohormone prosystemin requires processing for signal biogenesis and biological activity. The identification of phytaspases as the proteases involved in prosystemin maturation provides insight into the mechanisms of wound signaling in tomato. Our data also suggest a novel role for cell death-related proteases in mediating defense signaling in plants.

[Is celecoxib a safe alternative for the Fernand Widal syndrome?]

The Fernand Widal syndrome is a set of associations between asthma, nasal polyposis and aspirin sensitivity. Selective cyclo-oxygenase 2 (COX 2) inhibitors are recognized as being a therapeutic alternative in cases needing analgesic or anti-inflammatory treatment. In a retrospective study, we have compiled data concerning oral provocation tests (OPT) undertaken with celecoxib, one of most the selective COX 2 inhibitors, in eight patients with the Fernand Widal syndrome. They were compared with twenty-seven control patients with sensitivity to aspirin or non-steroidal anti-inflammatories, manifesting as asthma, urticaria or rhino-conjunctivitis. Four patients with the Fernand Widal syndrome developed bronchospasm after taking the usually recommended daily dose of celecoxib while all the control patients tolerated it. The Fernand Widal patients who reacted during the OPT had a lower threshold of reactivity to aspirin, a more severe reaction with aspirin, and/or more severe asthma. In patients with the Fernand Widal syndrome, celecoxib is not always a possible alternative to non-steroidal anti-inflammatory drugs. Its introduction must be carried out in a hospital environment under medical supervision.

Simultaneous Quantitative Detection of Relevant Biomarkers in Breast Cancer by Quantitative Real-Time PCR

The assessment of ERα, PgR and HER2 status is routinely performed today to determine the endocrine responsiveness of breast cancer samples. Such determination is usually accomplished by means of immunohistochemistry and in case of HER2 amplification by means of fluorescent in situ hybridization (FISH). The analysis of these markers can be improved by simultaneous measurements using quantitative real-time PCR (Qrt-PCR). In this study we compared Qrt-PCR results for the assessment of mRNA levels of ERα, PgR, and the members of the human epidermal growth factor receptor family, HER1, HER2, HER3 and HER4. The results were obtained in two independent laboratories using two different methods, SYBR Green I and TaqMan probes, and different primers. By linear regression we demonstrated a good concordance for all six markers. The quantitative mRNA expression levels of ERα, PgR and HER2 also strongly correlated with the respective quantitative protein expression levels prospectively detected by EIA in both laboratories. In addition, HER2 mRNA expression levels correlated well with gene amplification detected by FISH in the same biopsies. Our results indicate that both Qrt-PCR methods were robust and sensitive tools for routine diagnostics and consistent with standard methodologies. The developed simultaneous assessment of several biomarkers is fast and labor effective and allows optimization of the clinical decision-making process in breast cancer tissue and/or core biopsies.

An OPR3-independent pathway uses 4,5-didehydrojasmonate for jasmonate synthesis

Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele. Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the β-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.

Post-translational maturation of IDA, a peptide signal controlling floral organ abscission in Arabidopsis

The abscission of sepals, petals and stamens in Arabidopsis flowers is controlled by a peptide signal called IDA (Inflorescence Deficient in Abscission). IDA belongs to the large group of small post-translationally modified signaling peptides that are synthesized as larger precursors and require proteolytic processing and specific side chain modifications for signal biogenesis. Using tissue-specific expression of proteinase inhibitors as a novel approach for loss-of-function analysis, we recently identified the peptidases responsible for IDA maturation within the large family of subtilisin-like proteinases (subtilases; SBTs). Further biochemical and physiological assays identified three SBTs (AtSBT5.2, AtSBT4.12, AtSBT4.13) that cleave the IDA precursor to generate the N-terminus of the mature peptide. The C-terminal processing enzyme(s) remain(s) to be identified. While proline hydroxylation was suggested as additional post-translational modification required for IDA maturation, hydroxylated and non-hydroxylated IDA peptides were found to be equally active in bioassays for abscission.

A novel subtilase inhibitor in plants shows structural and functional similarities to protease propeptides

The propeptides of subtilisin-like serine proteinases (subtilases, SBTs) serve dual functions as intramolecular chaperones that are required for enzyme folding and as inhibitors of the mature proteases. SBT propeptides are homologous to the I9 family of protease inhibitors that have only been described in fungi. Here we report the identification and characterization of subtilisin propeptide-like inhibitor 1 (SPI-1) from Arabidopsis thaliana Sequence similarity and the shared β-α-β-β-α-β core structure identified SPI-1 as a member of the I9 inhibitor family and as the first independent I9 inhibitor in higher eukaryotes. SPI-1 was characterized as a high-affinity, tight-binding inhibitor of Arabidopsis subtilase SBT4.13 with K_d and K_i values in the picomolar range. SPI-1 acted as a stable inhibitor of SBT4.13 over the physiologically relevant range of pH, and its inhibitory profile included many other SBTs from plants but not bovine chymotrypsin or bacterial subtilisin A. Upon binding to SBT4.13, the C-terminal extension of SPI-1 was proteolytically cleaved. The last four amino acids at the newly formed C terminus of SPI-1 matched both the cleavage specificity of SBT4.13 and the consensus sequence of Arabidopsis SBTs at the junction of the propeptide with the catalytic domain. The data suggest that the C terminus of SPI-1 acts as a competitive inhibitor of target proteases as it remains bound to the active site in a product-like manner. SPI-1 thus resembles SBT propeptides with respect to its mode of protease inhibition. However, in contrast to SBT propeptides, SPI-1 could not substitute as a folding assistant for SBT4.13.

Precursor processing for plant peptide hormone maturation by subtilisin-like serine proteinases

Peptide hormones that regulate plant growth and development are derived from larger precursor proteins by proteolytic processing. Our study addressed the role of subtilisin-like proteinases (SBTs) in this process. Using tissue-specific expression of proteinase inhibitors as a tool to overcome functional redundancy, we found that SBT activity was required for the maturation of IDA (INFLORESCENCE DEFICIENT IN ABSCISSION), a peptide signal for the abscission of floral organs in Arabidopsis We identified three SBTs that process the IDA precursor in vitro, and this processing was shown to be required for the formation of mIDA (the mature and bioactive form of IDA) as the endogenous signaling peptide in vivo. Hence, SBTs act as prohormone convertases in plants, and several functionally redundant SBTs contribute to signal biogenesis.

Dirigent Protein Mode of Action Revealed by the Crystal Structure of AtDIR6

Dirigent proteins impart stereoselectivity to phenoxy radical coupling reactions in plants and, thus, play an essential role in the biosynthesis of biologically active natural products. This includes the regioselective and enantioselective coupling and subsequent cyclization of two coniferyl alcohol radicals to pinoresinol as the committed step of lignan biosynthesis. The reaction is controlled by dirigent proteins, which, depending on the species and protein, direct the reaction to either (+)- or (-)-pinoresinol. We present the crystal structure of the (-)-pinoresinol forming DIRIGENT PROTEIN6 (AtDIR6) from Arabidopsis (Arabidopsis thaliana) with data to 1.4 Å resolution. The structure shows AtDIR6 as an eight-stranded antiparallel β-barrel that forms a trimer with spatially well-separated cavities for substrate binding. The binding cavities are two lobed, exhibiting two opposing pockets, each lined with a set of hydrophilic and potentially catalytic residues, including essential aspartic acids. These residues are conserved between (+) and (-)-pinoresinol-forming DIRs and required for activity. The structure supports a model in which two substrate radicals bind to each of the DIR monomers. With the aromatic rings fixed in the two pockets, the propionyl side chains face each other for radical-radical coupling, and stereoselectivity is determined by the exact positioning of the side chains. Extensive mutational analysis supports a previously unrecognized function for DIRs in catalyzing the cyclization of the bis-quinone methide reaction intermediate to yield (+)- or (-)-pinoresinol.