Irradiance-dependent regulation of gravitropism by red light in protonemata of the moss Ceratodon purpureus

Apical cells of protonemata of the moss Ceratodon purpureus (Hedw.) Brid. are negatively gravitropic in the dark and positively phototropic in red light. Various fluence rates of unilateral red light were tested to determine whether both tropisms operate simultaneously. At irradiances ≥140 nmol m⁻² s⁻¹ no gravitropism could be detected and phototropism predominated, despite the presence of amyloplast sedimentation. Gravitropism occurred at irradiances lower than 140 nmol m⁻² s⁻¹ with most cells oriented above the horizontal but not upright. At these low fluence rates, phototropism was indistinct at 1 g but apparent in microgravity, indicating that gravitropism and phototropism compete at 1 g. The frequency of protonemata that were negatively phototropic varied with the fluence rate and the duration of illumination, as well as with the position of the apical cell before illumination. These data show that the fluence rate of red light regulates whether gravitropism is allowed or completely repressed, and that it influences the polarity of phototropism and the extent to which apical cells are aligned in the light path. Received: 19 January 1999 / Accepted: 19 March 1999     

Expression and characterization of bispecific single-chain Fv fragments produced in transgenic plants.

We describe the expression of the bispecific antibody biscFv2429 in transgenic suspension culture cells and tobacco plants. biscFv2429 consists of two single-chain antibodies, scFv24 and scFv29, connected by the Trichoderma reesi cellobiohydrolase I linker. biscFv2429 binds two epitopes of tobacco mosaic virus (TMV): the scFv24 domain recognizes neotopes of intact virions, and the scFv29 domain recognizes a cryptotope of the TMV coat protein monomer. biscFv2429 was functionally expressed either in the cytosol (biscFv2429-cyt) or targeted to the apoplast using a murine leader peptide sequence (biscFv2429-apoplast). A third construct contained the C-terminal KDEL sequence for retention in the ER (biscFv2429-KDEL). Levels of cytoplasmic biscFv2429 expression levels were low. The highest levels of antibody expression were for apoplast-targeted biscFv2429-apoplast and ER-retained biscFv2429-KDEL that reached a maximum expression level of 1.65% total soluble protein in transgenic plants. Plant-expressed biscFv2429 retained both epitope specificities, and bispecificity and bivalency were confirmed by ELISA and surface plasmon resonance analysis. This study establishes plant cells as an expression system for bispecific single-chain antibodies for use in medical and biological applications.     

Discovery of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent and selective PI3Kδ inhibitors

As demonstrated in preclinical animal models, the disruption of PI3Kδ expression or its activity leads to a decrease in inflammatory and immune responses. Therefore, inhibition of PI3Kδ may provide an alternative treatment for autoimmune diseases, such as RA, SLE, and respiratory ailments. Herein, we disclose the identification of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent, selective and orally bioavailable PI3Kδ inhibitors. The lead compound demonstrated efficacy in an in vivo mouse KLH model.     

Biochemical and functional characterization of anti-HIV antibody-ELP fusion proteins from transgenic plants

The stability and recovery of recombinant proteins expressed in plants are improved by fusion to elastin-like peptides (ELPs). In order to test the suitability of ELP for the production of pharmaceutical proteins, transgenic plants were created that individually expressed the light and heavy chains of the broadly neutralizing anti-human immunodeficiency virus type 1 (anti-HIV-1) monoclonal antibody 2F5, which is being evaluated as a microbicide component. The antibody chains were expressed both with and without a C-terminal ELP fusion. Crossing these plants in all combinations resulted in transgenic lines producing the full antibody in four formats, with ELP on either the light or heavy chains, on both or on neither. Characterization of the affinity-purified antibodies by surface plasmon resonance spectroscopy showed that the kinetic binding parameters were identical to those of a Chinese hamster ovary (CHO) cell counterpart lacking ELP. N -Glycan analysis showed that all four derivatives contained predominantly oligo-mannose-type N -glycans and that the ELP fusions had no significant effect on N -glycan structure. It was concluded that ELP fusion to the light chain, heavy chain or both chains of a plant-derived antibody had no adverse affects on protein quality, but had a positive impact on the yield. ELP fusions do not interfere with folding, assembly, trafficking in the secretory pathway or post-translational modification, but enhance stability whilst at the same time simplifying recovery.     

Allogeneic Non-Adherent Bone Marrow Cells Facilitate Hematopoietic Recovery but Do Not Lead to Allogeneic Engraftment

Background

Non adherent bone marrow derived cells (NA-BMCs) have recently been described to give rise to multiple mesenchymal phenotypes and have an impact in tissue regeneration. Therefore, the effects of murine bone marrow derived NA-BMCs were investigated with regard to engraftment capacities in allogeneic and syngeneic stem cell transplantation using transgenic, human CD4⁺, murine CD4^−/−, HLA-DR3⁺ mice.

Methodology/Principal Findings

Bone marrow cells were harvested from C57Bl/6 and Balb/c wild-type mice, expanded to NA-BMCs for 4 days and characterized by flow cytometry before transplantation in lethally irradiated recipient mice. Chimerism was detected using flow cytometry for MHC-I (H-2D[b], H-2K[d]), mu/huCD4, and huHLA-DR3). Culturing of bone marrow cells in a dexamethasone containing DMEM medium induced expansion of non adherent cells expressing CD11b, CD45, and CD90. Analysis of the CD45⁺ showed depletion of CD4⁺, CD8⁺, CD19⁺, and CD117⁺ cells. Expanded syngeneic and allogeneic NA-BMCs were transplanted into triple transgenic mice. Syngeneic NA-BMCs protected 83% of mice from death (n = 8, CD4⁺ donor chimerism of 5.8±2.4% [day 40], P<.001). Allogeneic NA-BMCs preserved 62.5% (n = 8) of mice from death without detectable hematopoietic donor chimerism. Transplantation of syngeneic bone marrow cells preserved 100%, transplantation of allogeneic bone marrow cells 33% of mice from death.

Conclusions/Significance

NA-BMCs triggered endogenous hematopoiesis and induced faster recovery compared to bone marrow controls. These findings may be of relevance in the refinement of strategies in the treatment of hematological malignancies.     

Utilization of oligo‐ and polysaccharides at microgram‐per‐litre levels in freshwater by Flavobacterium johnsoniae

Aims: To obtain a bacterial strain that can be used to quantify biodegradable polysaccharides at concentrations of a few micrograms per litre in freshwater. Methods and Results: Flavobacterium johnsoniae strain A3 was isolated from tap water supplemented with laminarin, pectin or amylopectin at 100 μg C l^?1 and river Rhine water. The organism utilized 14 of 23 oligo‐ and polysaccharides, and 1 of 9 monosaccharides, but none of the sugar acids, sugar alcohols, carboxylic acids or aromatic acids tested at 10 μg C l^?1. Amino acids promoted growth of strain A3, but not in coculture with assimilable organic carbon (AOC) test strain Pseudomonas fluorescens P17, which utilized these compounds more rapidly than strain A3. Compounds released by strain P17 and AOC test strain Spirillum sp. NOX grown on acetate promoted the growth of strain A3 at N_max values of ≥ 2 × 10⁵ CFU ml^?1 of strain P17 and ≥ 5 × 10⁵ CFU ml^?1 of strain NOX. Significant growth of strain A3 was observed in surface water and in tap water in the presence of strain P17 (N_max P17 < 2 × 10⁵ CFU ml^?1). Conclusions: Strain A3 utilizes oligo‐ and polysaccharides at microgram‐per‐litre levels. In surface water and in tap water, the organism was able to utilize compounds that were not utilized by strain P17. These compounds may include oligo‐ and/or polysaccharides. Significance and Impact of the Study: Phytoplanktonic and bacterial polysaccharides can constitute an important biodegradable fraction of natural organic matter in water and may promote growth of heterotrophic bacteria during water treatment and drinking water distribution. Strain A3 can be used to quantify a group of compounds that includes oligo‐ and polysaccharides at microgram‐per‐litre levels in freshwater.     

Oval cell proliferation in p16INK4a expressing mouse liver is triggered by chronic growth stimuli.

Terminal differentiation requires molecules also involved in aging such as the cell cycle inhibitor p16(INK4a).Like other organs, the adult liver represents a quiescent organ with terminal differentiated cells, hepatocytes and cholangiocytes. These cells retain the ability to proliferate in response to liver injury or reduction of liver mass. However, under conditions which prevent mitotic activation of hepatocytes, regeneration can occur instead from facultative hepatic stem cells.For therapeutic application a non-toxic activation of this stem cell compartment is required. We have established transgenic mice with conditional overexpression of the cell cycle inhibitor p16(INK4a) in hepatocytes and have provoked and examined oval cell activation in adult liver in response to a range of proliferative stimuli.We could show that the liver specific expression of p16(INK4a) leads to a faster differentiation of hepatocytes and an activation of oval cells already in postnatal mice without negative consequences on liver function.     

Vibrio cholerae O139 persists in Dhaka,Bangladesh since 1993

BackgroundAfter a multi-country Asian outbreak of cholera due to Vibrio cholerae serogroup O139 which started in 1992, it is rarely detected from any country in Asia and has not been detected from patients in Africa.Methodology/Principal findingsWe extracted surveillance data from the Dhaka and Matlab Hospitals of International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) to review trends in isolation of Vibrio cholerae O139 in Bangladesh. Data from the Dhaka Hospital is a 2% sample of > 100,000 diarrhoeal patients treated annually. Data from the Matlab Hospital includes all diarrhoeal patients who hail from the villages included in the Matlab Health and Demographic Surveillance System. Vibrio cholerae O139 was first isolated in Dhaka in 1993 and had been isolated every year since then except for a gap between 2005 and 2008. An average of thirteen isolates was detected annually from the Dhaka Hospital during the last ten years, yielding an estimated 650 cases annually at this hospital. During the last ten years, cases due to serogroup O139 represented 0.47% of all cholera cases; the others being due to serogroup O1. No cases with serogroup O139 were identified at Matlab since 2006. Clinical signs and symptoms of cholera due to serogroup O139 were similar to cases due to serogroup O1 though more of the O139 cases were not dehydrated. Most isolates of O139 remained sensitive to tetracycline, ciprofloxacin, and azithromycin, but they became resistant to erythromycin starting in 2009.Conclusions/SignificanceCholera due to Vibrio cholerae serogroup O139 continues to cause typical cholera in Dhaka, Bangladesh.     

Focus on Water: Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance

Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (K_leaf). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in K_leaf at declining leaf water potential (Ψ_leaf). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of K_leaf with mild dehydration (i.e. the initial slope of the K_leaf versus Ψ_leaf curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus Ψ_leaf curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions.As leaves open their stomata to capture CO₂ for photosynthesis, water is lost to transpiration, which needs to be replaced by flow through the hydraulic system. The leaf hydraulic system has two components, which act essentially in series: the pathways for water movement through the xylem from the petiole to leaf minor veins, and those through the living bundle sheath and mesophyll cells to the sites of evaporation (Tyree and Zimmermann, 2002; Sack et al., 2004; Sack and Holbrook, 2006). The decline in leaf hydraulic conductance (K_leaf) with dehydration may thus depend on both components. The importance of the xylem component is well established. Vein xylem embolism and cell collapse have been observed in dehydrating leaves (Salleo et al., 2001; Cochard et al., 2004a; Johnson et al., 2009), and computer modeling and experimental work showed that species with high major vein length per leaf area (VLA; i.e. for the first three vein-branching orders) were more resistant to hydraulic decline, providing more pathways around embolisms (Scoffoni et al., 2011). However, the physical impacts of dehydration on the extraxylem pathways have not been studied, even though in turgid leaves these pathways account for 26% to 88% of leaf hydraulic resistance (i.e. of 1/K_leaf), depending on species (Sack et al., 2003a; Cochard et al., 2004b). The aim of this study was to determine whether leaf shrinkage during dehydration relates to the decline of K_leaf as well as the structural determinants of leaf shrinkage.The shrinkage of leaves with dehydration has drawn attention for over 100 years. Leaves shrink in their area (Bogue, 1892; Gardner and Ehlig, 1965; Jones, 1973; Tang and Boyer, 2007; Blonder et al., 2012) and, considered in relative terms, even more strongly in their thickness (Fig. 1; Meidner, 1952; Gardner and Ehlig, 1965; Downey and Miller, 1971; Syvertsen and Levy, 1982; Saini and Rathore, 1983; Burquez, 1987; McBurney, 1992; Sancho-Knapik et al., 2010, 2011). Leaves fluctuate in thickness daily and seasonally according to transpiration (Kadoya et al., 1975; Tyree and Cameron, 1977; Fensom and Donald, 1982; Rozema et al., 1987; Ogaya and Peñuelas, 2006; Seelig et al., 2012). Indeed, the relation of leaf thickness to water status is so tight that using leaf thickness to guide irrigation has led to water savings of up to 45% (Seelig et al., 2012).Open in a separate windowFigure 1.Sketches of a fully turgid leaf (A) versus a strongly dehydrated leaf (B; drawings based on leaf cross sections of sunflower in Fellows and Boyer, 1978). Note the strong reduction in leaf thickness, cell thickness, and intercellular airspaces in the dehydrated leaf. Epidermal cells are shrunk in the dehydrated leaf, inducing whole-leaf area shrinkage. Note that this sketch represents shrinkage for a typical drought-sensitive species. Many species such as oaks (Quercus spp.) will experience less thickness shrinkage and an increase in intercellular airspace (see “Discussion”). [See online article for color version of this figure.]Previous studies of leaf shrinkage with progressive dehydration have tended to focus on single or few species. These studies showed that thickness declines with water status in two phases. Before the bulk leaf turgor loss point (TLP; leaf water potential [Ψ_leaf] at TLP) is reached, the slope of leaf thickness versus Ψ_leaf or relative water content (RWC) is shallower than past TLP for most species (Meidner, 1955, Kennedy and Booth, 1958, Burquez, 1987, McBurney, 1992, Sancho-Knapik et al., 2010, 2011). This is because before TLP, declining Ψ_leaf is strongly driven by declines in turgor pressure, which have a relatively low impact on cell and airspace volume, whereas past the TLP, declining Ψ_leaf depends only on solute concentration, which increases in inverse proportion as cell water volume declines while airspaces may shrink or expand (Tyree and Hammel, 1972, Sancho-Knapik et al., 2011). However, the steepness of the slope of leaf thickness versus Ψ_leaf before TLP seems to vary strongly across species (Meidner, 1955; Kennedy and Booth, 1958; Fellows and Boyer, 1978; Burquez, 1987; Colpitts and Coleman, 1997; Sancho-Knapik et al., 2010).A high leaf cell volume and turgor is crucial to physiological processes (Boyer, 1968; Lawlor and Cornic, 2002). Shrinkage may affect cell connectivity and water transport (Sancho-Knapik et al., 2011). However, no studies have tested for a possible relationship of leaf shrinkage with the decline of K_leaf during dehydration. Such an association would arise if, across species, shrinkage occurred simultaneously with vein xylem embolism or if tissue shrinkage led to declines in the extraxylem hydraulic conductance.To refine our hypotheses, we modified a computer model of the leaf hydraulic system (Cochard et al., 2004b; McKown et al., 2010; Scoffoni et al., 2011) to predict the impact of losses of xylem and extraxylem conductance on the response of K_leaf to dehydration. We characterized the degree of leaf shrinkage in thickness, in the thickness of cells and airspaces within the leaf, and in leaf area for 14 species diverse in phylogeny, leaf traits, and drought tolerance. We hypothesized that loss of extraxylem hydraulic conductance should have a greater impact on K_leaf at less negative water potentials when xylem tensions are too weak to trigger embolism and induce dramatic declines in K_leaf. We hypothesized that species with greater degrees of shrinkage before TLP would experience greater loss of K_leaf. Furthermore, we hypothesized that species from moist habitats would have greater degrees of shrinkage.For insight into the mechanisms and consequences of leaf shrinkage, we also investigated the relationships of 18 indices of leaf shrinkage with a wide range of aspects of leaf structure and composition, including gross morphology, leaf venation architecture, parameters of pressure-volume curves, and leaf water storage. We hypothesized that, across species, shrinkage in whole leaf, cell, and intercellular airspace thickness would be lower for species with greater allocation to structural rigidity and osmotic concentration, and thus shrinkage would be positively correlated with a lower modulus of elasticity (ε), less negative osmotic pressure at full turgor (π_o), lower leaf mass per area (LMA), and lower leaf density. Additionally, we tested the longstanding hypothesis that species with higher major VLA and/or minor VLA (i.e. the fourth and higher vein-branching orders) would shrink less in area and/or thickness with dehydration (Gardner and Ehlig, 1965). Finally, we tested the ability of dehydrated leaves to recover in size with rehydration. We hypothesized that recovery would be greater for mildly than for strongly dehydrated leaves and that species with greater leaf shrinkage would be better able to recover from shrinkage.