Characterization of Ni-resistant bacteria in the rhizosphere of the hyperaccumulator <Emphasis Type="Italic">Alyssum murale</Emphasis> by 16S rRNA gene sequence analysis

The diversity of 184 isolates from rhizosphere and bulk soil samples taken from the Ni hyperaccumulator Alyssum murale, grown in a Ni-rich serpentine soil, was determined by 16S rRNA gene analysis. Restriction digestion of the 16S rRNA gene was used to identify 44 groups. Representatives of each of these groups were placed within the phyla Proteobacteria, Firmicutes and Actinobacteria by 16S rRNA gene sequence analysis. By combining the 16S rRNA gene restriction data with the gene sequence analysis it was concluded that 44.6% (82/184) of the isolates were placed within the phylum Proteobacteria, among these 35.9% (66/184) were placed within the class α-Proteobacteria, and 20.7% (38/184) had 16S rRNA gene sequences indicative of bacteria within genera that form symbioses with legumes (rhizobia). Of the remaining isolates, 44.6% (82/184) and 5.4% (10/184) were placed within the phyla Actinobacteria and Firmicutes, respectively. No placement was obtained for a small number (10/184) of the isolates. Bacteria of the phyla Proteobacteria and Actinobacteria were the most numerous within the rhizosphere of A. murale and represented 32.1% (59/184) and 42.9% (79/184) of all isolates, respectively. The approach of using 16S rRNA gene sequence analysis in this study has enabled a comprehensive characterization of bacteria that predominate in the rhizosphere of A. murale growing in Ni-contaminated soil.     

Tissue Cultures of Phaseolus vulgaris L.

Abstract

Callus production and plant regeneration from different explants of Phaseolus vulgaris L. cv. Giza are reported. Calli cultures were induced from leaf, hypocotyl, embryo and root explants. Rapid growth of callus was achieved by leaf explants cultured on MS salts, B5 vitamins and supplemented with 2,4— dichlorophenoxyacetic acid (2, 4—D)+0.5 mg/l kinetin (kin). Addition of casein hydrolysate at 2 g/l to maintenance medium enhanced callus growth and hindered the early appearance of necrotic parts. This report also provides a detailed method for production of multiple shoots directly from the wounded edges of immature cotyledon explant via organogenesis on 1 mg/l benzyladenine (BA) or indirectly on 0.5 mg/l naphthaleneacetic acid (NAA)+2 mg/l BA. The regeneration of bean plants through the two ways described here (direct or indirect) may be of use in genetic improvement of bean.     

Human CD8+ T cells display a differential ability to undergo cytokine-driven bystander activation

A subset of CD44^hiCD8⁺ T cells in some, but not all mice, can be induced to rapidly secrete IFNγ during infection with Listeria monocytogenes. This response is dependent on the presence of both IL-12 and IL-18 and does not require engagement of the T cell receptor. In this study, we demonstrate that human CD8⁺ T cells also vary widely in their ability to secrete IFNγ within 15 h of either Listeria infection or cytokine stimulation. The magnitude of the rapid IFNγ response correlated more closely with the intrinsic responsiveness of the T cells to cytokine stimulation rather than the amount of IL-12 produced. CD8⁺ T cells from 2 out of 16 blood donors (12.5%) failed to generate a significant IFNγ response. These results demonstrate that bystander activation of CD8⁺ T cells varies among individuals and validate further study of the differential responses observed using BALB/c vs. C57BL/6 mice.     

Exercise-induced adaptations of cardiac redox homeostasis and remodeling in heterozygous SOD2-knockout mice

A reduced expression of the manganese-dependent superoxide dismutase (SOD2) is characterized by increased cardiac oxidative stress. Oxidative stress has also been described in situations of physical exercise. We investigated the influence of physical exercise (EX; treadmill 1 h/day at 15 m/min, 5 days/wk, at an angle of 5° for a duration of 8 wk) on cardiac function [heart frequency (HF), echocardiography, morphometry], oxidative stress [reactive oxygen species (ROS)], and antioxidative defence capacity (peroxiredoxin 1-6) in male SOD2-knockout (SOD2_EX) and wild-type mice (WT_EX) compared with untrained age-matched animals (WT_CON; SOD2_CON). In SOD2_CON, heart weight, cardiomyocyte diameter, and cardiac ROS were significantly larger and peroxiredoxin isoforms 4-6 lower than in WT_CON. The vessel-to-cardiomyocyte ratio, cardiac VEGF-concentration, and cardiac function were similar in SOD2_CON and WT_CON. Both groups tolerated the exercise protocol well. In WT, exercise significantly increased vessel-to-cardiomyocyte ratio and ROS-generation and downregulated peroxiredoxin isoforms 4-6 and VEGF generation. The vessel-to-cardiomyocyte ratio, cardiac VEGF concentration, and cardiac ROS were not altered in SOD2_EX compared with SOD2_CON, but a significant upregulation of cardiac peroxiredoxin 1 and 4 was observed. Similar to the result observed in WT_EX, peroxiredoxin 3 was upregulated in SOD2_EX. Chronic exercise shifted the (mal)adaptive hypertrophic into a compensated dilated cardiac phenotype in SOD2_EX. In conclusion, downregulation of SOD2 induces a maladaptive cardiac hypertrophy. In this situation, physical exercise results in a further deterioration of cardiac remodeling despite an upregulation of the antioxidative defense system.     

Root-synthesized cytokinins improve shoot growth and fruit yield in salinized tomato (Solanum lycopersicum L.) plants

Salinity limits crop productivity, in part by decreasing shoot concentrations of the growth-promoting and senescence-delaying hormones cytokinins. Since constitutive cytokinin overproduction may have pleiotropic effects on plant development, two approaches assessed whether specific root-localized transgenic IPT (a key enzyme for cytokinin biosynthesis) gene expression could substantially improve tomato plant growth and yield under salinity: transient root IPT induction (HSP70::IPT) and grafting wild-type (WT) shoots onto a constitutive IPT-expressing rootstock (WT/35S::IPT). Transient root IPT induction increased root, xylem sap, and leaf bioactive cytokinin concentrations 2- to 3-fold without shoot IPT gene expression. Although IPT induction reduced root biomass (by 15%) in control (non-salinized) plants, in salinized plants (100?mM NaCl for 22?d), increased cytokinin concentrations delayed stomatal closure and leaf senescence and almost doubled shoot growth (compared with WT plants), with concomitant increases in the essential nutrient K(+) (20%) and decreases in the toxic ion Na(+) (by 30%) and abscisic acid (by 20-40%) concentrations in transpiring mature leaves. Similarly, WT/35S::IPT plants (scion/rootstock) grown with 75?mM NaCl for 90?d had higher fruit trans-zeatin concentrations (1.5- to 2-fold) and yielded 30% more than WT/non-transformed plants. Enhancing root cytokinin synthesis modified both shoot hormonal and ionic status, thus ameliorating salinity-induced decreases in growth and yield.     

Oral Transmission of Listeria monocytogenes in Mice via Ingestion of Contaminated Food

L. monocytogenes are facultative intracellular bacterial pathogens that cause food borne infections in humans. Very little is known about the gastrointestinal phase of listeriosis due to the lack of a small animal model that closely mimics human disease. This paper describes a novel mouse model for oral transmission of L. monocytogenes. Using this model, mice fed L. monocytogenes-contaminated bread have a discrete phase of gastrointestinal infection, followed by varying degrees of systemic spread in susceptible (BALB/c/By/J) or resistant (C57BL/6) mouse strains. During the later stages of the infection, dissemination to the gall bladder and brain is observed. The food borne model of listeriosis is highly reproducible, does not require specialized skills, and can be used with a wide variety of bacterial isolates and laboratory mouse strains. As such, it is the ideal model to study both virulence strategies used by L. monocytogenes to promote intestinal colonization, as well as the host response to invasive food borne bacterial infection.     

Omics of root-to-shoot signaling under salt stress and water deficit

Maximizing crop yield depends on the leaves receiving an optimal supply of water, mineral nutrients, small organic molecules, proteins, and hormones from the root system via the xylem. Soil drying and salinization alter these xylem fluxes, and modern omics techniques offer unparalleled opportunities to understand the complexity of these responses. Although absolute xylem concentrations of any constituent depend on the genotype and xylem sap sampling methodology, analysis of the relative changes in concentrations has revealed some conserved behavior. Typically, these stresses increase xylem concentrations of the plant hormone abscisic acid (ABA) that limits crop water loss, but decrease the concentrations of certain cytokinins that stimulate expansive growth and prevent premature leaf senescence. Further understanding of the ionic and biophysical alterations in the rhizosphere environment that cause increased xylem concentrations of the ethylene precursor (ACC) is needed. Interactions of these plant hormones with plant nutrient status and xylem nutrient delivery may be important in tuning plant responses to their environment. Xylem proteomics is an emerging area that will help understand mechanisms of plant stress adaptation. Using omics techniques to underpin rootstock-mediate plant improvement is likely to improve crop yields in dry or saline soil.     

A radial glia-specific role of RhoA in double cortex formation

The positioning of neurons in the cerebral cortex is of crucial importance for its function as highlighted by the severe consequences of migrational disorders in patients. Here we show that genetic deletion of the small GTPase RhoA in the developing cerebral cortex results in two migrational disorders: subcortical band heterotopia (SBH), a heterotopic cortex underlying the normotopic cortex, and cobblestone lissencephaly, in which neurons protrude beyond layer I at the pial surface of the brain. Surprisingly, RhoA(-/-) neurons migrated normally when transplanted into wild-type cerebral cortex, whereas the converse was not the case. Alterations in the radial glia scaffold are demonstrated to cause these migrational defects through destabilization of both the actin and the microtubules cytoskeleton. These data not only demonstrate that RhoA is largely dispensable for migration in neurons but also showed that defects in radial glial cells, rather than neurons, can be sufficient to produce SBH.