Restricted cell elongation in Arabidopsis hypocotyls is associated with a reduced average pectin esterification level

<p>Abstract</p> <p>Background</p> <p>Cell elongation is mainly limited by the extensibility of the cell wall. Dicotyledonous primary (growing) cell walls contain cellulose, xyloglucan, pectin and proteins, but little is known about how each polymer class contributes to the cell wall mechanical properties that control extensibility.</p> <p>Results</p> <p>We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in <it>Arabidopsis </it>hypocotyls. When the average DE% falls below this level, as in two gibberellic acid (GA) mutants <it>ga1-3 </it>and <it>gai</it>, and plants expressing pectin methyl-esterase (<it>PME1</it>) from <it>Aspergillus aculeatus</it>, then hypocotyl elongation is reduced.</p> <p>Conclusion</p> <p>Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA. At high average DE% other components of the cell wall limit GA-induced growth.</p

Plasmid maintenance in Escherichia coli K-12

This study investigated the maintenance of several plasmid derivatives of pBR322 and ColEl present within Escherichia coli K-12, with a view to establishing a strategy that would ensure the stable maintenance of plasmid pBR322 and the identification of a postulated partitioning function on plasmid ColEl. Two strategies were adopted. The first of these used selective nitrogen-limited chemostat culture of a glutamate-dependent strain of E.coli, carrying a pBR322 derivative expressing glutamate dehydrogenase. Using this approach, it was found that the plasmid conferred a reproductive advantage and persisted, during nitrogen limitation, for several generations beyond that of pBR322 under glucose- or phosphate- limited conditions. The second strategy used nonselective chemostat culture of a strain of E.coli carrying derivatives of pBR322 encoding stability functions from either plasmid pSClOl, the partitioning region par, or plasmid R1, the cell division/plasmid inheritance coupling region parB. Although these plasmids persisted for many generations beyond that of pBR322 under similar chemostat culture conditions, no conclusions could be made with respect to the ability of these functions to ensure stable plasmid maintenance, since the copy numbers of the respective plasmids were several-fold greater than that of pBR322, a factor that in itself would contribute to the segregational stability of the plasmids. Plasmid- free segregants which did arise were found not to be isogenic with the host strain. These mutants exhibited an increased resistance to U.V.-light irradiation, a mucoid colony phenotype, an altered cell division cycle, giving rise to minicell, filament and Y-shaped cellular morphologies, an enhanced ability to form tandemly repeated plasmid multimers and an altered sensitivity to the DNA gyrase specific antibiotics novobiocin and nalidixic acid. A study of plasmid configuration in Ion and Ion sul strains of E.coli, which share similar phenotypic characteristics with the above mutants, revealed that strains which carry a sul or azi mutation express an enhanced capacity for plasmid multimerization. Finally, no conclusive evidence could be obtained to indicate the presence of a partitioning function on plasmid ColEl. This study concludes by postulating several factors which may affect the maintenance of plasmids in E.coli K-12

Conservation of the PBL-RBOH immune module in land plants

The rapid production of reactive oxygen species (ROS) is a key signaling output in plant immunity. In the angiosperm model species Arabidopsis thaliana (hereafter Arabidopsis), recognition of non- or altered-self elicitor patterns by cell-surface immune receptors activates the receptor-like cytoplasmic kinases (RLCKs) of the AVRPPHB SUSCEPTIBLE 1 (PBS1)-like (PBL) family, particularly BOTRYTIS-INDUCED KINASE1 (BIK1).$^{1}$$^{,}$$^{2}$$^{,}$$^{3}$ BIK1/PBLs in turn phosphorylate the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) to induce apoplastic ROS production.$^{4}$$^{,}$$^{5}$ PBL and RBOH functions in plant immunity have been extensively characterized in flowering plants. Much less is known about the conservation of pattern-triggered ROS signaling pathways in non-flowering plants. In this study, we show that in the liverwort Marchantia polymorpha (hereafter Marchantia), single members of the RBOH and PBL families, namely MpRBOH1 and MpPBLa, are required for chitin-induced ROS production. MpPBLa directly interacts with and phosphorylates MpRBOH1 at specific, conserved sites within its cytosolic N terminus, and this phosphorylation is essential for chitin-induced MpRBOH1-mediated ROS production. Collectively, our work reveals the functional conservation of the PBL-RBOH module that controls pattern-triggered ROS production in land plants

The phagocytosis oxidase/Bem1p domain-containing protein PB1CP negatively regulates the NADPH oxidase RBOHD in plant immunity

Perception of pathogen-associated molecular patterns (PAMPs) by surface-localized pattern recognition receptors activates RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) through direct phosphorylation by BOTRYTIS-INDUCED KINASE 1 (BIK1) and induces the production of reactive oxygen species (ROS). RBOHD activity must be tightly controlled to avoid the detrimental effects of ROS, but little is known about RBOHD downregulation. To understand the regulation of RBOHD, we used co-immunoprecipitation of RBOHD with mass spectrometry analysis and identified PHAGOCYTOSIS OXIDASE/BEM1P (PB1) DOMAIN-CONTAINING PROTEIN (PB1CP). PB1CP negatively regulates RBOHD and the resistance against the fungal pathogen Colletotrichum higginsianum. PB1CP competes with BIK1 for binding to RBOHD in vitro. Furthermore, PAMP treatment enhances the PB1CP-RBOHD interaction, thereby leading to the dissociation of phosphorylated BIK1 from RBOHD in vivo. PB1CP localizes at the cell periphery and PAMP treatment induces relocalization of PB1CP and RBOHD to the same small endomembrane compartments. Additionally, overexpression of PB1CP in Arabidopsis leads to a reduction in the abundance of RBOHD protein, suggesting the possible involvement of PB1CP in RBOHD endocytosis. We found PB1CP, a novel negative regulator of RBOHD, and revealed its possible regulatory mechanisms involving the removal of phosphorylated BIK1 from RBOHD and the promotion of RBOHD endocytosis

The Relative Humidity in an Isentropic Advection–Condensation Model: Limited Poleward Influence and Properties of Subtropical Minima

An idealized model of advection and condensation of water vapor is considered as a representation of processes influencing the humidity distribution along isentropic surfaces in the free troposphere. Results are presented for how the mean relative humidity distribution varies in response to changes in the distribution of saturation specific humidity and in the amplitude of a tropical moisture source. Changes in the tropical moisture source are found to have little effect on the relative humidity poleward of the subtropical minima, suggesting a lack of poleward influence despite much greater water vapor concentrations at lower latitudes. The subtropical minima in relative humidity are found to be located just equatorward of the inflection points of the saturation specific humidity profile along the isentropic surface. The degree of mean subsaturation is found to vary with the magnitude of the meridional gradient of saturation specific humidity when other parameters are held fixed. The atmospheric relevance of these results is investigated by comparison with the positions of the relative humidity minima in reanalysis data and by examining poleward influence of relative humidity in simulations with an idealized general circulation model. It is suggested that the limited poleward influence of relative humidity may constrain the propagation of errors in simulated humidity fields

***TEST SUBMISSION*** BMJ-15: Acceptance within last 3 months (01/03/2020); Online publication within 12 months (10/12/2020); Embargo (10/09/2021) less than 12 months from pub date; VoR

From UAT Test publisher via Jisc Publications RouterHistory: accepted 2020-03-01, epub 2020-12-10Article version: VoRPublication status: PublishedAbstract: TEST: THIS IS A PUBLICATIONS ROUTER TEST SUBMISSION. Objectives: To quantify post-colonoscopy colorectal cancer (PCCRC) rates in England by using recent World Endoscopy Organisation guidelines, compare incidence among colonoscopy providers, and explore associated factors that could benefit from quality improvement initiatives. Design: Population based cohort study. Setting: National Health Service in England between 2005 and 2013. Population: All people undergoing colonoscopy and subsequently diagnosed as having colorectal cancer up to three years after their investigation (PCCRC-3yr). Main outcome measures: National trends in incidence of PCCRC (within 6-36 months of colonoscopy), univariable and multivariable analyses to explore factors associated with occurrence, and funnel plots to measure variation among providers. Results: The overall unadjusted PCCRC-3yr rate was 7.4% (9317/126 152), which decreased from 9.0% in 2005 to 6.5% in 2013 (P<0.01). Rates were lower for colonoscopies performed under the NHS bowel cancer screening programme (593/16 640, 3.6%), while they were higher for those conducted by non-NHS providers (187/2009, 9.3%). Rates were higher in women, in older age groups, and in people with inflammatory bowel disease or diverticular disease, in those with higher comorbidity scores, and in people with previous cancers. Substantial variation in rates among colonoscopy providers remained after adjustment for case mix. Conclusions: Wide variation exists in PCCRC-3yr rates across NHS colonoscopy providers in England. The lowest incidence was seen in colonoscopies performed under the NHS bowel cancer screening programme. Quality improvement initiatives are needed to address this variation in rates and prevent colorectal cancer by enabling earlier diagnosis, removing premalignant polyps, and therefore improving outcomes

Conservation of the PBL-RBOH immune module in land plants

The rapid production of reactive oxygen species (ROS) is a key signaling output in plant immunity. In the angiosperm model species Arabidopsis thaliana (hereafter Arabidopsis), recognition of non- or altered-self elicitor patterns by cell-surface immune receptors activates the receptor-like cytoplasmic kinases (RLCKs) of the AVRPPHB SUSCEPTIBLE 1 (PBS1)-like (PBL) family, particularly BOTRYTIS-INDUCED KINASE1 (BIK1).1,2,3 BIK1/PBLs in turn phosphorylate the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) to induce apoplastic ROS production.4,5 PBL and RBOH functions in plant immunity have been extensively characterized in flowering plants. Much less is known about the conservation of pattern-triggered ROS signaling pathways in non-flowering plants. In this study, we show that in the liverwort Marchantia polymorpha (hereafter Marchantia), single members of the RBOH and PBL families, namely MpRBOH1 and MpPBLa, are required for chitin-induced ROS production. MpPBLa directly interacts with and phosphorylates MpRBOH1 at specific, conserved sites within its cytosolic N terminus, and this phosphorylation is essential for chitin-induced MpRBOH1-mediated ROS production. Collectively, our work reveals the functional conservation of the PBL-RBOH module that controls pattern-triggered ROS production in land plants

Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase

Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex

Solution of the Navier–Stokes Equations for the Processes of Inertial Gas Dynamic Separation in the Curvilinear Channels

Аналіз результатів показав, що вісесимметричний газовий потік рідини уздовж вигнутого каналу утворює періодичні вихрі в порожнинах по зовнішньому радіусу, а також пульсації динамічного тиску. Подальші дослідження будуть спрямовані на чисельне моделювання газодинамічної сепарації в криволінійних каналах з гнучкими стінками.У результаті аналітичного розв'язання рівнянь Нав'є-Стокса для потоку газу в плоскому напівкруглому кільцевому каналі визначені радіальна і окружна компоненти швидкості з урахуванням граничних умов, обмежень і гіпотез. Отримані рівняння для визначення витрат газу і вираз для розподілу тиску.В результате аналитического решения уравнений Навье-Стокса для потока газа в плоском полукруглом кольцевом канале определены радиальная и окружная компоненты скорости с учетом граничных условий, ограничений и гипотез. Получены уравнения для определения расхода газа и выражение для распределения давления.In this paper as a result of the analytical solution of the Navier-Stokes equations for gas flow in the plane semicircular annular channel the radial and circumference velocity components were determined taking into account boundary conditions, limitations and hypotheses. Equation for gas leakages determination and expression for pressure distribution were received