THE COMPARATIVE DEMOGRAPHY OF RECIPROCALLY SOWN POPULATIONS OF PHLOX DRUMMONDII HOOK. I. SURVIVORSHIPS,FECUNDITIES, AND FINITE RATES OF INCREASE

Comparative demography of reciprocally sown populations for all stages of the life cycle of the winter annual, Phlox drummondii, was recorded for two seasons in natural sites. The sites investigated covered the natural range of the species and were separated by linear distances ranging from 10 to over 500 kilometers. Interpopulational variation was observed in all stages of the life cycle. Prereproductive survivorship ranged from 0 to 92 percent. Fecundity per plant ranged from 0 to 81 seeds. Finite rates of increase ranged from 0 to 34.1 yr^?1. The experimental populations with low values were growing in sites that received little rainfall or had experienced an insect or fungal infestation. The populations with high growth rates occurred in the northern sites which received greater rainfall. The relative fitness of individuals from the alien populations was compared to the local populations for all stages of the life cycle. The alien relative fitness for survivorship averaged 0.72. The average relative fitness of aliens for fecundity was 0.71 and that for finite rate of increase was 0.57. The life history parameters found in Phlox populations differ from one part of the range to another so that aliens have lower relative fitnesses than individuals indigenous to the site.     

WNK1 is an assembly factor for the human ER membrane protein complex

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Antioxidant mechanisms of polyphenolic caffeic acid oligomers, constituents of Salvia officinalis

Caffeic acid, rosmarinic acid and oligomers of caffeic acid with multiple catechol groups are all constituents of Salvia officinalis. Their antioxidant potential was investigated with regard to their radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic studies revealed very high rate constants with hydroxyl radicals. Evidence from kinetic modeling calculations suggested an unusual complex behavior due to the presence of both O4- and O3-semiquinones and formation and decay of a hydroxyl radical adduct at the vinyl side chain. The radical structures observed by EPR spectroscopy after autoxidation in slightly alkaline solutions were only partially identified due to their instability and generally represented dissociated O4-semiquinones. Hybrid density-functional calculations of the potential radical structures showed distinct differences between the resonance stabilization of the O4- and O3-semiquinones of caffeic and dihydrocaffeic acids, reflected also in the considerably faster decay of the O3-semiquinone observed by pulse radiolysis. No evidence was found for dimerization reactions via Cbeta radicals typical for lignin biosynthesis.     

Anthropogenic N deposition and the fate of 15NO 3 − in a northern hardwood ecosystem

Human activity has substantially increased atmospheric NO ₃ ^– deposition in many regions of the Earth, which could lead to the N saturation of terrestrial ecosystems. Sugar maple (Acer saccharum Marsh.) dominated northern hardwood forests in the Upper Great Lakes region may be particularly sensitive to chronic NO ₃ ^– deposition, because relatively moderate experimental increases (three times ambient) have resulted in substantial N leaching over a relatively short duration (5–7 years). Although microbial immobilization is an initial sink (i.e., within 1–2 days) for anthropogenic NO ₃ ^– in this ecosystem, we have an incomplete understanding of the processes controlling the longer-term (i.e., after 1 year) retention and flow of anthropogenic N. Our objectives were to determine: (i) whether chronic NO ₃ ^– additions have altered the N content of major ecosystem pools, and (ii) the longer-term fate of ¹⁵NO ₃ ^– in plots receiving chronic NO ₃ ^– addition. We addressed these objectives using a field experiment in which three northern hardwood plots receive ambient atmospheric N deposition (ca. 0.9 g N m^–2 year^–1) and three plots which receive ambient plus experimental N deposition (3.0 g NO₃ ^–-N m^–2 year^–1). Chronic NO ₃ ^– deposition significantly increased the N concentration and content (g N/m²) of canopy leaves, which contained 72% more N than the control treatment. However, chronic NO ₃ ^– deposition did not significantly alter the biomass, N concentration or N content of any other ecosystem pool. The largest portion of ¹⁵N recovered after 1 year occurred in overstory leaves and branches (10%). In contrast, we recovered virtually none of the isotope in soil organic matter (SOM), indicating that SOM was not a sink for anthropogenic NO ₃ ^– over a 1 year duration. Our results indicate that anthropogenic NO ₃ ^– initially assimilated by the microbial community is released into soil solution where it is subsequently taken up by overstory trees and allocated to the canopy. Anthropogenic N appears to be incorporated into SOM only after it is returned to the forest floor and soil via leaf litter fall. Short- and long-term isotope tracing studies provided very different results and illustrate the need to understand the physiological processes controlling the flow of anthropogenic N in terrestrial ecosystems and the specific time steps over which they operate.     

Metabolic biotinylation as a probe of supramolecular structure of the triad junction in skeletal muscle

Excitation-contraction coupling in skeletal muscle involves conformational coupling between dihydropyridine receptors (DHPRs) in the plasma membrane and ryanodine receptors (RyRs) in the sarcoplasmic reticulum. However, it remains uncertain what regions, if any, of the two proteins interact with one another. Toward this end, it would be valuable to know the spatial interrelationships of DHPRs and RyRs within plasma membrane/sarcoplasmic reticulum junctions. Here we describe a new approach based on metabolic incorporation of biotin into targeted sites of the DHPR. To accomplish this, cDNAs were constructed with a biotin acceptor domain (BAD) fused to selected sites of the DHPR, with fluorescent protein (XFP) attached at a second site. All of the BAD-tagged constructs properly targeted to junctions (as indicted by small puncta of XFP) and were functional for excitation-contraction coupling. To determine whether the introduced BAD was biotinylated and accessible to avidin (approximately 60 kDa), myotubes were fixed, permeablized, and exposed to fluorescently labeled avidin. Upon expression in beta1-null or dysgenic (alpha1S-null) myotubes, punctate avidin fluorescence co-localized with the XFP puncta for BAD attached to the beta1a N- or C-terminals, or the alpha1S N-terminal or II-III loop. However, BAD fused to the alpha1S C-terminal was inaccessible to avidin in dysgenic myotubes (containing RyR1). In contrast, this site was accessible to avidin when the identical construct was expressed in dyspedic myotubes lacking RyR1. These results indicate that avidin has access to a number of sites of the DHPR within fully assembled (RyR1-containing) junctions, but not to the alpha1S C-terminal, which appears to be occluded by the presence of RyR1.     

Thrombospondin-2 and SPARC/osteonectin are critical regulators of bone remodeling

Thrombospondin-2 (TSP2) and osteonectin/BM-40/SPARC are matricellular proteins that are highly expressed by bone cells. Mice deficient in either of these proteins show phenotypic alterations in the skeleton, and these phenotypes are most pronounced under conditions of altered bone remodeling. For example, TSP2-null mice have higher cortical bone volume and are resistant to bone loss associated with ovariectomy, whereas SPARC-null mice have decreased trabecular bone volume and fail to demonstrate an increase in bone mineral density in response to a bone-anabolic parathyroid hormone treatment regimen. In vitro, marrow stromal cell (MSC) osteoprogenitors from TSP2-null mice have increased proliferation but delayed formation of mineralized matrix. Similarly, in cultures of SPARC-null MSCs, osteoblastic differentiation and mineralized matrix formation are decreased. Overall, both TSP2 and SPARC positively influence osteoblastic differentiation. Intriguingly, both of these matricellular proteins appear to impact MSC fate through mechanisms that could involve the Notch signaling system. This review provides an overview of the role of TSP2 and SPARC in regulating bone structure, function, and remodeling, as determined by both in vitro and in vivo studies.     

Ecological investigations on the zooplankton community of Balsfjorden,northern Norway: Generation cycles,and variations in body weight and body content of carbon and nitrogen related to overwintering and reproduction in the copepod Calanus finmarchicus (Gunnerus)

The generation cycles of Calanus finmarchicus (Gunnerus) are described together with the seasonal variations in length, wet wt, dry wt, carbon content, nitrogen content and $\text{C}\text{N}$ ratio in copepodite stage IV, V and stage VI males and females from Balsfjorden (69°21′N: 19°06′E), a subarctic fjord in northern Norway. C. finmarchicus overwinters in copepodite stage IV (≈ 20%) or V (≈80%) and produces one generation a year. Variations in body weight and body content of carbon and nitrogen in the different copepodite stages showed a pronounced seasonal pattern. For instance, the $\text{C}\text{N}$ ratio was lowest (4.9) in adult females during the spawning period. Copepodite stage IV and V had higher $\text{C}\text{N}$ values in summer and autumn (12 to 14) than in spring (8 to 10). Variations in length, weight and chemical composition revealed that the overwintering stock of C. finmarchicus went through two growth phases during this period. From September to January no significant changes in the measured variables were detected. During the second phase of the overwintering period, January to April, the different stages showed a profound decrease in weight and change in chemical composition. This seemed to be connected with the onset of sexual differentiation in stage V starting in January, subsequent moulting into adults and gonad maturation in these adults. These results are further discussed in relation to the different prevailing hypotheses concerning overwintering strategy in Calanus species.     

A BioBrick compatible strategy for genetic modification of plants

ABSTRACT: BACKGROUND: Plant biotechnology can be leveraged to produce food, fuel, medicine, and materials. Standardized methods advocated by the synthetic biology community can accelerate the plant design cycle, ultimately making plant engineering more widely accessible to bioengineers who can contribute diverse creative input to the design process. RESULTS: This paper presents work done largely by undergraduate students participating in the 2010 International Genetically Engineered Machines (iGEM) competition. Described here is a framework for engineering the model plant Arabidopsis thaliana with standardized, BioBrick compatible vectors and parts available through the Registry of Standard Biological Parts (www.partsregistry.org). This system was used to engineer a proof-of-concept plant that exogenously expresses the taste-inverting protein miraculin. CONCLUSIONS: Our work is intended to encourage future iGEM teams and other synthetic biologists to use plants as a genetic chassis. Our workflow simplifies the use of standardized parts in plant systems, allowing the construction and expression of heterologous genes in plants within the timeframe allotted for typical iGEM projects.     

Predicting plant responses to mycorrhizae: integrating evolutionary history and plant traits

We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.