Metal Tolerance and Accumulation Ability of the Ni Hyperaccumulator Streptanthus polygaloides Gray (Brassicaceae)

High concentrations of metals occur in some plant species (termed hyperaccumulators), such as the Ni hyperaccumulator Streptanthus polygaloides. We determined the tolerance of S. polygaloides to, and its accumulation abilities for, six metals (Ni, Zn, Cu, Co, Mn, and Pb). Potting mix concentrations used for all metals ranged from 0 to 1200 μg/g dry weight. For Ni, a treatment of 1600 μg/g was included. For Mn, treatments of 1600, 2000, and 2500 μg/g also were used, and for Pb these concentrations plus 3500 μg/g were included. Germination, plant number per pot, and size at days 30 and 39, number of plants at the end of the experiment (day 49), flower production, and metal concentration in the aboveground biomass were documented. Lead and Ni showed no consistent effects on plant performance, but yielded increased tissue metal concentrations. Streptanthus polygaloides was more sensitive to Co, Cu, and Zn, as ≥ 400 mg/g significantly suppressed plant growth, survival, and flower production. Tissue metal concentrations also were increased to maxima of 1500 μg Co/g, 120 μg Cu/g, and 6000 μg Zn/g. Manganese affected S. polygaloides less markedly, as ≥ 800 mg/kg decreased growth, survival, and flower production. Maximum tissue Mn concentration was 2900 μg/g. We concluded that S. polygaloides would be an appropriate phytoextractor for soils contaminated with Ni or low levels of Co but would not be useful for Cu, Zn, Mn, and Pb.     

Nickel hyperaccumulation by Streptanthus polygaloides protects against the folivore Plutella xylostella (Lepidoptera: Plutellidae)

We determined the effectiveness of Ni as an elemental defence of Streptanthus polygaloides (Brassicaceae) against a crucifer specialist folivore, diamondback moth (DBM), Plutella xylostella. An oviposition experiment used arrays of S. polygaloides grown on Ni-amended (high-Ni) soil interspersed with plants grown on unamended (low-Ni) soil and eggs were allowed to hatch and larvae fed freely among plants in the arrays. We also explored oviposition preference by allowing moths to oviposit on foil sheets coated with high- or low-Ni plant extract. This was followed by an experiment using low-Ni plant extract to which varying amounts of Ni had been added and an experiment using sheets coated with sinigrin (allyl glucosinolate) as an oviposition stimulant. Diamondback moths laid 2.5-fold more eggs on low-Ni plants than on high-Ni plants and larval feeding was greater on low-Ni plants. High-Ni plants grew twice as tall, produced more leaves, and produced almost 3.5-fold more flowers. Low-Ni plants contained more allyl glucosinolate than high-Ni plants and moths preferred to oviposit on foil sheets dipped in low-Ni plant extract. Moths showed no preference when Ni concentration of low-Ni extract was varied and overwhelmingly preferred sinigrin coated sheets. We conclude that Ni hyperaccumulation is an effective elemental defence against this herbivore, increasing plant fitness through a combination of toxicity to DBM larvae and decreased oviposition by adults.     

ANTIOXIDANT ENZYMES AS DEFENSE MECHANISM AGAINST OXIDATIVE STRESS IN MIDGUT TISSUE AND HEMOCYTES OF Bombyx mori LARVAE SUBJECTED TO VARIOUS STRESSORS

In this study, larvae of silkworm Bombyx mori were subjected to low temperature, hypoxia, and viral infection to evaluate stressor‐mediated oxidative stress (OS) and the induction of antioxidant enzymes (AOEs). Exposure to cold, hypoxia, and nuclear polyhedral virus for 24 h resulted in a significant increase in hydrogen peroxide generation with concomitant increase in lipid peroxidation (LPO) and protein carbonyl levels in midgut and hemocytes. AOEs such as superoxide dismutase and catalase also increased significantly in both the tissues and the increased AOEs reverted to control values during recovery. Ontogenic stages of the larvae showed a diminishing ability of the tissues to overcome OS induced by the stressors. A significant increase in AOE activity during short stress period indicated a possible transitory defense mechanism to avoid OS‐induced cell damage.     

Outline of A New Approach to Evaluate Ecological Integrity of Salt Marshes

The integrity of coastal salt marshes can be determined from the extent to which they provide key ecosystem services: food and habitat for fish and wildlife, good water quality, erosion and flood control, and recreation and cultural use. An outline of a new approach for linking ecosystem services with metrics of structure and function to evaluate the ecological integrity of salt marshes is described. One main objective of the approach is to determine whether differences in structure and function can be detected among salt marshes with similar geomorphology and hydrology but different degrees of anthropogenic stress. The approach is currently being applied to salt marshes of Narragansett Bay, RI, USA. Stable nitrogen isotopic ratios of the marsh biota reflected the nitrogen sources from the adjacent watersheds and were significantly correlated with percent residential land use. Results show that plant zonation significantly ( r = —0.82; p < 0.05) relates with percent residential land use and is potentially a sensitive indicator of anthropogenic disturbance of New England salt marshes. We are currently examining species diversity, denitrification rates, and susceptibility to erosion among the sites for additional indicators of salt marsh condition. Our results to date suggest that this approach will provide the methods needed for managers to systematically monitor and evaluate the integrity of salt marshes     

Influence of Herbicide Application to Soybeans on Soybean Cyst Nematode Egg Hatching

The hatching of Heterodera glycines eggs in soybean root exudates collected after postemergence application of three herbicides, and the hatching potential of H. glycines eggs from females feeding on herbicide-treated plants, were measured in vitro. Hatching in all root exudate solutions (RES) was greater than in deionized water but less than in 0.003 M ZnSO₄ solution. Filtering RES with a 0.22-μm-filter increased H. glycines hatching in RES. Application of acifluorfen, bentazon, and lactofen to foliage of soybean plants inhibited hatching of H. glycines eggs from the same plants. Hatching in RES from the different herbicide-treated soybeans was similar. Application of crop oil concentrate and non-ionic surfactant adjuvant to foliage did not affect hatching of H. glycines eggs from soybean plants.     

Determination of platelet-activating factor and alkyl-ether phospholipids by gas chromatography-mass spectrometry via direct derivatization

A mass spectrometric method has been developed for the quantitative analysis of platelet-activating factor (PAF) and lyso-platelet-activating factor (lyso-PAF) based on electron-capture gas chromatography-mass spectrometry using a stable-isotope dilution technique. The cleavage and derivatization was accomplished in a single step by direct reaction of phospholipid with pentafluorobenzoyl chloride at 150 degrees C. Spectroscopic and chromatographic data indicated that PAF and lyso-PAF were converted into derivatives containing a pentafluorobenzoyl group in place of the original phosphocholine group with 95 and 51% yield, respectively. Additionally, in the lyso-PAF derivative, the free hydroxyl group was found to be replaced by chlorine. Phosphatidylcholines containing an arachidonoyl group can be derivatized with a solution of PFBCl/chloroform at 120 degrees C for 18 h, producing 90% derivative. Analysis by GC/MS and LC/MS allowed the detection of 1 or 250 pg derivative, respectively, injected onto the column with S/N greater than 3. Newly available analogues of high isotopic purity containing either three or four deuterium atoms located in the 1-O-hexadecyl chain were used as internal standards. The developed GC/MS assay was used to quantitate PAF and lyso-PAF in rabbit leukocytes before and after stimulation with calcium ionophore. The levels of PAF in unstimulated cells were in the order of 2.27 pmol/10(6) cells and increased about 17-fold during 10-min stimulation with 2 microM ionophore A23187. The lyso-PAF levels in resting cells were in the order of 3.76 pmol/10(6) cells and increased 1.7-fold during stimulation. This assay exhibited satisfactory sensitivity, reproducibility, and accuracy.     

Properties of P-form DNA as revealed by circular dichroism

Investigations of DNA using CD spectroscopy show that the P-form is available in a wide variety of methanol–ethanol mixtures when the water content is low. Increasing the temperature or the ethanol content of a 95% methanol solution causes DNA to undergo a cooperative transition to the P-form. However, this transition cannot be reversed on cooling, or on adding methanol. Thus P-form DNA appears to be stable at high methanol concentrations, but it is usually not observed because the DNA is trapped by a kinetic barrier. P-form DNA will instantaneously assume the native B-form on addition of water, confirming earlier reports that P-form DNA is not strand separated [E. Kay (1976) Biochemistry 15 , 5241]. CD spectra extended to 190 nm show that there is no base–base interaction in the P-form. However, the P-form is extremely stable to heat denaturation in solvents which promote hydrogen bonding between the base pairs. A number of models that can account for the properties of P-form DNA are discussed.     

Determination of trans-arachidonic acid isomers in human blood plasma

Endogenous trans fatty acids originate from diet, but recent studies also suggest that cis-trans isomerization of fatty acids is possible by nitrogen dioxide radical, a product of NO and nitrite oxidation. We developed a method for quantitative analysis of four trans-arachidonic acids (TAA) in human plasma using isotopic dilution gas chromatography/mass spectrometry (GC/MS) with deuterium-labeled internal standard. Esterification of the plasma fatty acid extract with pentafluorobenzyl (PFB) bromide followed by high-performance liquid chromatography purification yielded a fairly pure fraction containing TAA-PFB esters that was analyzed by GC/MS. Partial separation of the TAA isomers was obtained on various GC columns. Comparison of the retention time with the synthetic standards revealed that all four TAA isomers are present in human plasma. The mean concentration of TAA in human plasma was 20.2ng/ml. The levels of isomers were 12.48+/-1.28, 2.75+/-0.39, and 4.99+/-0.74ng/ml for 5E-AA + 11E-AA, 8E-AA, and 14E-AA, respectively. The identification of TAA in plasma suggests that isomerization of arachidonic acid occurs in vivo. Our method allows distinguishing between the dietary and the NO(2)-dependent mechanisms of trans fatty acid formation and will be useful in defining the role of TAA as an in vivo marker of nitrooxidative stress in clinical and experimental settings.     

Rap1 maintains adhesion between cells to affect Egfr signaling and planar cell polarity in Drosophila

The small GTPase Rap1 affects cell adhesion and cell motility in numerous developmental contexts. Loss of Rap1 in the Drosophila wing epithelium disrupts adherens junction localization, causing mutant cells to disperse, and dramatically alters epithelial cell shape. While the adhesive consequences of Rap1 inactivation have been well described in this system, the effects on cell signaling, cell fate specification, and tissue differentiation are not known. Here we demonstrate that Egfr-dependent cell types are lost from Rap1 mutant tissue as an indirect consequence of DE-cadherin mislocalization. Cells lacking Rap1 in the developing wing and eye are capable of responding to an Egfr signal, indicating that Rap1 is not required for Egfr/Ras/MAPK signal transduction. Instead, Rap1 regulates adhesive contacts necessary for maintenance of Egfr signaling between cells, and differentiation of wing veins and photoreceptors. Rap1 is also necessary for planar cell polarity in these tissues. Wing hair alignment and ommatidial rotation, functional readouts of planar cell polarity in the wing and eye respectively, are both affected in Rap1 mutant tissue. Finally, we show that Rap1 acts through the effector Canoe to regulate these developmental processes.     

Isotopic evidence of dietary variations and weaning practices in the Gaya cemetery at Yeanri,Gimhae, South Korea

Stable carbon and nitrogen isotope analyses were conducted to investigate dietary variation in human skeletons (n = 109) from the Gaya cemetery at Yeanri located near Gimhae City, South Korea. The cemetery contained three distinct grave types dating to 4th–7th century AD. The main purposes of this research were to reconstruct palaeodiet in the Gaya population and to explore correlations between stable isotope compositions and burial types, inferred age, and sex of these individuals. The isotopic data indicate that the people at Yeanri consumed a predominantly C₃‐based terrestrial diet supplemented with freshwater and/or marine resources. The comparison of isotopic results reveals significant differences in δ¹³C values among three adult burial types (wood‐cist coffin: ?18.5 ± 0.5‰, stone‐cist coffin: ?18.1 ± 0.6‰, mausoleum: ?17.8 ± 0.9‰). Males in wood‐cist and stone‐cist coffins have relatively more elevated mean δ¹³C and δ¹⁵N values than females. The isotopic ratios from the two adult age groups (21–40 years and 40–60 years) indicate that there was no significant dietary change in individuals with age. The isotope data from the infants and children suggest the weaning was a gradual process that was completed between 3 and 4 years of age in the Gaya population. This evidence indicates that the dietary variations within the cemetery reflect social status, sex, and childhood consumption patterns. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.