Ultrahigh CO2 levels enhances cuphea growth and morphogenesis

Applications of ultrahigh CO₂ treatments accelerated cuphea (Cuphea viscosissima × C. lanceolata ‘PSR23’) growth and development and aided in seedling establishment. The growth (fresh weight) and morphogenesis (number of leaves and roots and seedling length) were determined in cuphea seedlings exposed to 350, 1500, 3000, 10,000, or 30,000 μmol mol⁻¹ CO₂ for 30 days under greenhouse conditions. Greater CO₂ levels, especially the ultrahigh levels (i.e. ≥3000 μmol mol⁻¹ CO₂) resulted in significantly higher (P ≤ 0.05) fresh weights, leaf numbers, root numbers, and seedling lengths compared to seedlings grown under ambient air (350 μmol mol⁻¹ CO₂). For example, cuphea ‘PSR23’ Morris heavy seedlings showed the greatest seedling fresh weight, leaf number, root number, and seedling length when supplemented with 10,000 μmol mol⁻¹ CO₂ increasing 607%, 184%, 784%, and 175%, respectively, when compared to seedlings grown without CO₂ enrichment.     

Role of native soil biology in Brassicaceous seed meal-induced weed suppression

Biologically based weed control strategies are needed in organic and low-input systems. One promising practice is the application of Brassicaceous seed meal (BSM) residue, a byproduct of biodiesel production. When applied as a soil amendment, BSM residue has exhibited potential bioherbicide activity. In this study, tree fruit orchard soils were treated with various BSMs and the impact of Pythium on weed suppression was examined in field and greenhouse studies. Although weed control obtained in response to Brassicaceous residue amendments has been repeatedly attributed solely to release of allelopathic phytochemicals, multiple lines of evidence acquired in these studies indicate the involvement of a microbiological component. Reduced weed emergence and increased weed seedling mortality were not related to BSM glucosinolate content but were correlated with significant increases in resident populations of Pythium spp. in three different orchard soils. Seed meal of Brassica juncea did not amplify resident Pythium populations and did not suppress weed emergence. Application of Glycine max SM did stimulate Pythium spp. populations and likewise suppressed weed emergence. Application of a mefenoxam drench to Pythium-enriched soil significantly reduced weed suppression. These studies indicate that a microbial mechanism is involved in SM-induced weed suppression and that selective enhancement of resident pathogenic Pythium spp. can be utilized for the purpose of weed control.     

Serum complement activity in the three-toed amphiuma (Amphiuma tridactylum)

Some animals routinely endure serious injuries from predators or during intraspecific territorial conflicts. Such is the case for Amphiuma tridactylum, an aquatic salamander that lives in an environment rich in potentially infectious microbes, apparently with rare or no pathogenic infection. Some vertebrates possess innate immune mechanisms, but whether this is the case for Amphiuma is unknown. To assess this potential, plasma from 19 A. tridactylum was pooled and used for characterisation of serum complement activity. The ability of A. tridactylum plasma to hemolyse unsensitised sheep red blood cells (SRBCs) was titer-dependent, with low activity observed even at high plasma titers. The kinetic characterisation of SRBC hemolysis revealed that significant activity could be measured within 10 min of incubation, and maximal activity occurred within 60 min. The SRBC hemolysis by A. tridactylum plasma was also temperature-dependent, with maximal activity at 30 °C. In addition, this activity was sensitive to mild heat treatment, with 96% of activity inhibited by incubation at 56 °C for 30 min. The SRBC hemolysis could also be inactivated by pretreatment of the plasma with proteases, indicating that this activity was protein dependent. The activity required divalent metals ions, with activity inhibited by EDTA, citrate, or phosphate. However, the chelator-inhibited activity could be restored by the addition of excess Ca²⁺ or Mg²⁺, but not Cu²⁺ or Ba²⁺, indicating specificity of the divalent metal ion requirement. The sensitivity to heat, proteases, and divalent metal ion chelators strongly suggests that A. tridactylum plasma-mediated hemolysis of SRBCs is mediated by the serum complement system of proteins.     

Spatial patterns of shrub cover after different fire disturbances in the Pyrenees

? Woody encroachment into grasslands is a worldwide phenomenon. In the Pyrenees, fire has been used as a management tool to transform part of the encroached land to grassland.

? This study aims to compare the spatial patterns of shrub cover 4 y after 4 different fire disturbances (prescribed burning, repeated prescribed burning, wildfire in 20 year-old shrubs and wildfire in 5 year-old shrubs); and also to compare shrub cover after different fire disturbances, accounting for spatial autocorrelation. The study focuses on the shrub Cytisus balansae. Two-dimensional transects (20 × 0.5 m) were established to monitor shrub cover for 4 y after each disturbance type. Autoregressive models and Markov models were used with a Monte Carlo procedure to account for the presence of spatial autocorrelation.

? Shrub cover was greater after prescribed burning than after repeated prescribed burning, and it increased with shrub age before disturbance. Differences in spatial patterns were detected in shrub patch size, with repeated prescribed fires and wildfires reducing shrub patch size by half in comparison with prescribed burning.

? From the management point of view, the effects of repeated prescribed burning were similar to those of a wildfire on reducing shrub cover and shrub patch size.

     

Development of Contamination-Free Restriction Fragment Length Polymorphism Probes for the Obligate Biotroph Peronospora tabacina, an Oomycete Causing Blue Mold of Tobacco

ABSTRACT Peronospora tabacina is an obligately parasitic oomycete that causes blue mold, a devastating disease of tobacco. Genetic studies of this pathogen have been hampered by the lack of molecular markers. We generated a set of molecular markers for P. tabacina by collecting sporangiospores from infected tobacco leaves, extracting spore DNA, and cloning it in a plasmid vector. The resulting clones were then used to probe DNA from a collection of P. tabacina isolates to survey for polymorphisms. Most probes gave unexpected hybridization patterns with signal intensities that varied significantly from one DNA sample to another or between different DNA preparations of the same isolate. These results indicated that certain DNA preparations contained DNA from a source other than P. tabacina, which in turn suggested that some probes might have been derived from contaminating organisms present in the spore suspensions. Therefore, we characterized the inserts of several recombinant plasmids to determine their origins. Sequence analysis revealed that several of the inserts encoded peptides with similarity to bacterial proteins, suggesting that they were derived from bacterial contaminants. Of the remaining clones, five exhibited similarity to retroelements, one resembled eukaryotic helicase genes, and nine had no similarity to sequences in the databases. These were postulated to be true P. tabacina DNA clones. Verification of the origin of each probe was achieved by filtering a spore suspension, extracting DNA from the retentate and filtrate, and probing Southern blots of these DNA samples. These experiments confirmed the probe origins predicted by sequence analysis, resulting in the generation of 20 different restriction fragment length polymorphism probes that are specific for P. tabacina DNA. These probes should enable identification of reliable genetic markers for population studies of the blue mold organism.     

Effects of induction treatments on flowering in Populus deltoides

Stimulation of early flowering is required to shorten breeding cycles of eastern cottonwood (Populus deltoides Bartr. ex Marsh. var. deltoides), a commercially important and fast-growing hardwood species. A series of experiments was conducted to evaluate the influence of various treatments on flowering in rooted cuttings from mature and juvenile trees. A combined treatment of water stress, root pruning and paclobutrazol was applied to 3-month-old rooted cuttings from mature trees. These cuttings had been subjected to root restriction and long days. All treated plants flowered, whereas no untreated plants formed flower buds. One-year-old rooted cuttings from juvenile trees did not flower when treated with either paclobutrazol, paclobutrazol plus water stress, paclobutrazol plus root pruning, or paclobutrazol plus girdling. This was true both under continuous or periodic growth. Assessment of the lack of flowering in juvenile trees may require an integrated approach that investigates environmental or physiological stimuli, assimilate shift, gibberellic acid type and concentration, and flowering-time gene activity in the new shoots of mature and juvenile cottonwood trees.     

Isolation and characterization of pediatric canine bone marrow CD34+ cells

Historically, the dog has been a valuable model for bone marrow transplantation studies, with many of the advances achieved in the dog being directly transferable to human clinical bone marrow transplantation protocols. In addition, dogs are also a source of many well-characterized homologues of human genetic diseases, making them an ideal large animal model in which to evaluate gene therapy protocols. It is generally accepted that progenitor cells for many human hematopoietic cell lineages reside in the CD34+ fraction of cells from bone marrow, cord blood, or peripheral blood. In addition, CD34+ cells are the current targets for human gene therapy of diseases involving the hematopoietic system. In this study, we have isolated and characterized highly enriched populations of canine CD34+ cells isolated from dogs 1 week to 3 months of age. Bone marrow isolated from 2- to 3-week-old dogs contained up to 18% CD34+ cells and this high percentage dropped sharply with age. In in vitro 6-day liquid suspension cultures, CD34+ cells harvested from 3-week-old dogs expanded almost two times more than those from 3-month-old dogs and the cells from younger dogs were also more responsive to human Flt-3 ligand (Flt3L). In culture, the percent and number of CD34+ cells from both ages of dogs dropped sharply between 2 and 4 days, although the number of CD34+ cells at day 6 of culture was higher for cells harvested from the younger dogs. CD34+ cells harvested from both ages of dogs had similar enrichment and depletion values in CFU-GM methylcellulose assays. Canine CD34+/Rho123lo cells expressed c-kit mRNA while the CD34+/Rhohi cells did not. When transplanted to a sub-lethally irradiated recipient, CD34+ cells from 1- to 3-week-old dogs gave rise to both myeloid and lymphoid lineages in the periphery. This study demonstrates that canine CD34+ bone marrow cells have similar in vitro and in vivo characteristics as human CD34+ cells. In addition, ontogeny-related functional differences reported for human CD34+ cells appear to exist in the dog as well, suggesting pediatric CD34+ cells may be better targets for gene transfer than adult bone marrow. The demonstration of similarities between canine and human CD34+ cells enhances the dog as a large, preclinical model to evaluate strategies for improving bone marrow transplantation protocols, for gene therapy protocols that target CD34+ cells, and to study the engraftment potential of various cell populations that may contain hematopoietic progenitor cell activity.