The tomato mutation nxd1 reveals a gene necessary for neoxanthin biosynthesis and demonstrates that violaxanthin is a sufficient precursor for abscisic acid biosynthesis

Carotenoid pigments are indispensable for plant life. They are synthesized within plastids where they provide essential functions in photosynthesis. Carotenoids serve as precursors for the synthesis of the strigolactone phytohormones, which are made from β‐carotene, and of abscisic acid (ABA), which is produced from certain xanthophylls. Despite the significant progress that has been made in our understanding of the carotenoid biosynthesis pathway, the synthesis of the xanthophyll neoxanthin has remained unknown. We report here on the isolation of a tomato (Solanum lycopersicum) mutant, neoxanthin‐deficient 1 (nxd1), which lacks neoxanthin, and on the cloning of a gene that is necessary for neoxanthin synthesis in both tomato and Arabidopsis. The locus nxd1 encodes a gene of unknown function that is conserved in all higher plants. The activity of NXD1 is essential but cannot solely support neoxanthin synthesis. Lack of neoxanthin does not significantly reduce the fitness of tomato plants in cultivated field conditions and does not impair the synthesis of ABA, suggesting that in tomato violaxanthin is a sufficient precursor for ABA production in vivo.     

Effect of mannose-binding lectin from peanut and pea on the stem borer Chilo partellus

A mannose-binding lectin found in vegetative tissues of peanut, Arachis hypogaea, was compared with mannose-binding lectin from pea, Pisum sativum, for toxic effects on larvae of the stem borer Chilo partellus (Swinhoe). After 10 days, the mortality of larvae fed on artificial diet containing 0.5% (m/m) peanut lectin was 46.2%. The mortality of larvae fed on 1.0% peanut lectin was similar (48.1%) but insects were significantly smaller than those of the 0.5% treatment. Larvae of both lectin treatments stopped feeding within three days. Larval size and mortality was not significantly reduced by 0.1% peanut lectin and 1% heat-treated lectin did not show toxic effects. The mannose-binding lectin from pea was not toxic to C. partellus at concentrations up to 1%. Peanut lectin bound to the apical membranes of columnar epithelial cells in the mid-gut of C. partellus. This suggests that peanut lectin has an antinutritive action and that it may protect vegetative tissues of peanut against insect pests.     

Effects of pneumogastric nerve stimulation and injection of a beta 2 stimulant (terbutaline) on the lipid composition of the alveolar lining fluid and on pulmonary compliance in the rat

The effects of vagal stimulation and of terbutaline injection on lipidic composition of alveolar fluid and pulmonary compliance were studied. Three groups of rats were used: control, after right vagus nerve stimulation, after 0.2 mg terbutaline injection. The lungs of the rats were isolated. We studied pulmonary pressure-volume curves with air and we measured pulmonary compliance. We realised an alveolar lavage to obtain alveolar lipids. We observed: Vagus nerve stimulation and beta 2 agonist significantly increased fatty acids of total lipids respectively by 52.5% and 25.5% and phospholipids, respectively by 43.6% and 25.7%. beta 2 agonist did not change fatty acid composition of total lipids and phospholipids. Right vagus nerve stimulation increased the percentage of palmitic acid in phospholipids and decreased the percentage of saturated fatty acids and of palmitic acid in total lipids. Terbutaline injection induced more significant changes in pressure-volume curves and in pulmonary compliance than right vagus nerve stimulation. Our results suggest that both vagal stimulation and beta 2 agonists increase lipid release in alveolar lining, but only vagal stimulation modifies the composition of these lipids. These modifications could be, at least in part, correlated with the changes observed in the pressure-volume curves.     

Depth-dependent analysis of the role of collagen fibrils, fixed charges and fluid in the pericellular matrix of articular cartilage on chondrocyte mechanics

The pericellular matrix of articular cartilage has been shown to regulate the mechanical environment of chondrocytes. However, little is known about the mechanical role of collagen fibrils in the pericellular matrix, and how fibrils might help modulate strains acting on chondrocytes when cartilage is loaded. The primary objective was to clarify the effect of pericellular collagen fibrils on cell volume changes and strains during cartilage loading. Secondary objectives were to investigate the effects of pericellular fixed charges and fluid on cell responses. A microstructural model of articular cartilage, in which chondrocytes and pericellular matrices were represented with depth-dependent structural and morphological properties, was created. The extracellular matrix and pericellular matrices were modeled as fibril-reinforced, biphasic materials with swelling capabilities, while chondrocytes were assumed to be isotropic and biphasic with swelling properties. Collagen fibrils in the extracellular matrix were represented with an arcade-like architecture, whereas pericellular fibrils were assumed to run tangential to the cell surface. In the early stages of a stress-relaxation test, pericellular fibrils were found to sensitively affect cell volume changes, even producing a reversal from increasing to decreasing cell volume with increasing fibril stiffness in the superficial zone. Consequently, steady-state volume of the superficial zone cell decreased with increasing pericellular fibril stiffness. Volume changes in the middle and deep zone chondrocytes were smaller and opposite to those observed in the superficial zone chondrocyte. An increase in the pericellular fixed charge density reduced cell volumes substantially in every zone. The sensitivity of cell volume changes to pericellular fibril stiffness suggests that pericellular fibrils play an important, and as of yet largely neglected, role in regulating the mechanical environment of chondrocytes, possibly affecting matrix synthesis during cartilage development and degeneration, and affecting biosynthetic responses associated with articular cartilage loading.     

Granulocyte-macrophage colony-stimulating factor increases synthesis and expression of CR1 and CR3 by human peripheral blood neutrophils

Polymorphonuclear leukocytes (PMN) constitutively synthesize various plasma membrane proteins including CR1(3) (CD35), CR3 (or Mac-1) alpha-chain (CD11b) and MHC class I. PMN are also able to up-regulate rapidly the expression of CR1 and CR3 to the plasma membrane in response to agonists such as FMLP. To determine whether constitutive PMN translation was static or up-regulatable, PMN were cultured in the presence or absence of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) for 8 h. CR1, CR3 and class I proteins immunoprecipitated from lysates of 35S-methionine pulse-labeled PMN were resolved by SDS-PAGE, fluorographed and quantified by densitometry. GM-CSF-treated PMN synthesized 4.5-fold more class I protein, 3.7-fold more CR1, 2.4-fold more CD11b and 3.4-fold more CR3 beta-chain (CD18), compared with untreated control cells. Actinomycin D treatment of replicate samples of PMN decreased the amount of these proteins synthesized by each group of PMN from 30 to 90%, implying that continued translation was required for the increases in protein synthesis. Nascent CR and class I proteins were inserted into the plasma membrane of PMN, thereby supplementing the molecules already expressed on the cell surface. In addition to these longer term effects of GM-CSF, we observed its acute up-regulatory effects on PMN. GM-CSF induced a five- to 12-fold increase in the expression of CR1 and CR3 on the PMN cell surface within 30 min. These increases were both dose- and time-dependent with maximum up-regulation occurring at 25 pM and at 30 min. In contrast to the long term biosynthetic events, this rapid up-regulation was not dependent on protein synthesis but was due instead to mobilization of CR from intracellular compartments similar to those up-regulated by FMLP. These results demonstrate that PMN can respond to microenvironmental stimuli such as GM-CSF both by rapidly up-regulating and increasing translation and expression of functionally important plasma membrane proteins.     

Variable expression of lineage regulators in differentiated stromal cells indicates distinct mechanisms of differentiation towards common cell fate

Mesenchymal stem cells (MSCs) possess a multi-lineage differentiation capacity that makes them important players in the field of regenerative medicine. MSC populations derived from different tissues or donors have been shown to exhibit variable gene expression patterns. Further, it is widely acknowledged that MSC isolates are heterogeneous mixtures of cells at different developmental stages. However, the heterogeneity of expression of lineage regulators has not been linked to differentiation potential of different MSC populations towards mesenchymal lineages. Here, we analyzed variation of expression of differentiation markers across whole population and between single differentiating cells of multipotent stromal cell populations derived from adipose tissue (AdMSCs) and skin (FBs) of seven donors. The results of the analyses show that all cell populations exhibit similar differentiation potential towards adipocyte, osteoblast and chondrocyte lineages despite tissue type- and donor-specific variations of expression of differentiation-associated genes. Further, we detected variable expression of lineage regulators in individual differentiating cells. Together, our data indicate that single cells of stromal cell populations could use distinct molecular mechanisms to reach a common cell fate.     

Lambs with scrapie susceptible genotypes have higher postnatal survival

Background

Prion protein (PrP) alleles associated with scrapie susceptibility persist in many sheep populations even with high frequencies despite centuries of selection against them. This suggests that scrapie susceptibility alleles have a pleiotropic effect or are associated with fitness or other traits that have been subject to selection.

Methodology/Principal Findings

We genotyped all lambs in two scrapie-free Scottish Blackface sheep flocks for polymorphisms at codons 136, 154 and 171 of the PrP gene. We tested potential associations of the PrP genotype with lamb viability at birth and postnatal survival using a complementary log-log link function and a Weibull proportional hazard model, respectively. Here we show there is an association between PrP genotype, as defined by polymorphisms at codons 154 ad 171, and postnatal lamb survival in the absence of scrapie. Sheep carrying the wild-type ARQ allele have higher postnatal survival rates than sheep carrying the more scrapie-resistant alleles (ARR or AHQ).

Conclusion

The PrP genotypes associated with higher susceptibility to scrapie are associated with improved postnatal survival in the absence of the disease. This association helps to explain the existence, and in many instances the high frequency, of the ARQ allele in sheep populations.