Assessing the risk of invasive success in Pinus and Banksia in South African mountain fynbos

Abstract. South African mountain fynbos has been severely invaded by trees and shrubs introduced from other mediterranean-climate regions. Management of these invasions should involve controlling current invaders and screening future introductions. Invasion windows are described and functional groups are defined for pines based on life history attributes important for invasion in the fire-prone mountain fynbos. The most successful invasive pines here (Pinus halepensis, P. pinaster and P. radiata) are fire-resilient and have small seeds, low seed-wing loadings, short juvenile periods, moderate to high degrees of serotiny and relatively poor fire-tolerance as adults. Other species with these attributes, especially from mediterranean-climate regions, wouldbe high-risk introductions. Taxa in other functional groups have not become major weeds even with widespread man-aided dissemination. Experience with pine invaders was used to define functional groups in western Australian Banksia species (Proteaceae), shrubs and trees which include taxa with similar attributes to fynbos invaders (e.g. Hakea and Pinus spp.). Banksias have only recently been introduced to the Cape, and are likely to be increasingly cultivated for the cut flower market. Tall serotinous shrubs with many small seeds per plant, short juvenile periods and low fire tolerance were identified as high risk introductions. This group includes thicket-forming species which maintain very large viable seed banks, e.g. Banksia burdettii, B. hookeriana and B. leptophylla. Low sprouting shrubs with few large seeds per plant and long juvenile periods are unlikely to become invasive in mountain fynbos. The approach of defining functional groups based on life history attributes and invasion windows is valuable for predicting the probability of invasive success. Chance interactions suchas an opportunistic dispersal mutualism between Pinus pinea and an introduced squirrel sometimes confound these predictions and underscore the idiosyncracies inherent in biological invasions.     

Genetic variation in the horsetail Equisetum variegatum Schleich., an endangered species in the Parisian region

Equisetum variegatum Schleicher is a circumboreale species of horsetail. In France, it typically grows at high elevations but is very rare in lowlands. The genetic variation of these populations is described using isozyme electrophoresis and PCR-RFLP of chloroplast DNA. Sampled sites were chosen to represent central vs. marginal and/or endangered parts of the distribution area. Extensive clonal multiplication of plants together with the absence of local recruitment by sexual reproduction seem to be responsible for the low genetic diversity observed within populations. Since adaptive response to environmental changes ultimately relies on the presence of genetic variability, clonal populations of E. variegatum may be particularly vulnerable to disturbance. Moreover, in lowland populations, isolation gives no chance to recover new genotypes through migration events. The preservation of the two endangered populations is proposed by propagation by cuttings of all extant genetic individuals. In the case of a disappearance of one genotype in the field, a replacement will be possible. This plan may be sufficient to preserve E. variegatum in the French lowland for several years.     

Chronic Exposure of NG108-15 Cells to Amyloid β Peptide (Aβ1–42) Abolishes Calcium Influx via N-Type Calcium Channels

We investigated whether amyloid--peptide (A_1–42) has an effect on the elevations of the intracellular concentration of Ca²⁺ ions ([Ca²⁺]_i) induced by depolarizations of NG108-15 cells and on related Ca²⁺ channels. A_1–42 (10-1000 nM) had no immediate effect on depolarization-induced [Ca²⁺]_i elevations. [Ca²⁺]_i increases were slightly diminished in cells grown in the presence of 100 or 1000 nM A_1–42. Nifedipine (1 M) reduced these elevations equally in cells grown in the absence or presence of A_1–42. In contrast, the ability of -conotoxin GVIA to diminish the depolarization-induced [Ca²⁺]_i responses became lost in cells grown in the presence of 100 nM A_1–42. This indicates that the influx of calcium through the N-type Ca²⁺ channels was compromised by the chronic exposure of cells to a submicromolar concentration of A_1–42, presumably because of impairement of their function or diminished expression. This may be important in the pathogeny of Alzheimer's dementia in view of the pivotal role of N-type Ca²⁺ channels in neurotransmitter release.     

Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism. VI. Enzymatic studies of two mutants unable to convert inosinic acid to adenylic acid

Ade^–H and ade^–I are two auxotrophic mutants of Chinese hamster ovary (CHO-K1) cells which specifically require adenine as the purine source to grow. The enzymatic defects of these mutants were examined in cell-free extracts. It was found that ade^–H did not have any detectable adenylosuccinate synthetase activity and ade^–I was defective in the adenylosuccinate lyase enzyme. The relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discussed.This work was supported by research grants from the National Institute of Aging (AG00029) and the National Foundation, March of Dimes (1-423), and by a contract from the Center for Toxicological Research, Food and Drug Administration (72-213). David Patterson is a recipient of a Research Career Development Award from the National Institute of Arthritis, Metabolic and Digestive Diseases (AM00044).Contribution (No. 218) from the Eleanor Roosevelt Institute for Cancer Research.     

Expression of gibberellin 2-oxidase 4 from Arabidopsis under the control of a senescence-associated promoter results in a dominant semi-dwarf plant with normal flowering

Gibberellin (GA), a plant hormone, is involved in many aspects of plant growth and development both in vegetative and reproductive phases. GA2-oxidase plays a key role in the GA catabolic pathway to reduce bioactive GAs. We produced transgenic Arabidopsis plants expressing GA2-oxidase 4 (AtGA2ox4) under the control of a senescenceassociated promoter (SEN1). As we hypothesized, transgenic plants (SEN1::AtGA2ox4) exhibited a dominant semi-dwarf phenotype with a decrease of bioactive GAs (e.g., GA4 and GA1) up to two-fold compared to control plants. Application of bioactive GA3 resulted in increased shoot length, indicating that the GA signaling pathway functions normally in the SEN1::AtGA2ox4 plants. Expressions of other members of GA2-oxidase family, such as AtGA2ox1, AtGA2ox3, AtGA2ox6, and AtGA2ox8, were decreased slightly in the flower and silique tissues while GA biosynthetic genes (e.g., AtGA20ox1, AtGA20ox2 and AtGA3ox1) were not significantly changed in the SEN::AtGA2ox4 plants. Using proteome profiling (2-D PAGE followed by MALDI-TOF/MS), we identified 29 protein spots that were increased in the SEN1::AtGA2ox4 plants, but were decreased to wild-type levels by GA3 treatment. The majority were found to be involved in photosynthesis and carbon/energy metabolism. Unlike the previous constitutive over-expression of GA2-oxidases, which frequently led to floral deformity and/or loss of fertility, the SEN1::AtGA2ox4 plants retained normal floral morphology and seed production. Accordingly, the expressions of FT and CO genes remained unchanged in the SEN1::AtGA2ox4 plants. Taken together, our results suggest that the dominant dwarf trait carried by SEN1::AtGA2ox4 plants can be used as an efficient dwarfing tool in plant biotechnological applications.     

Evaluation of bacterial and archaeal diversity in the rumen of Xiangxi yellow cattle (Bos taurus) fed Miscanthus sinensis or common mixed feedstuff

Miscanthus sinensis is a potential biofuel that is distributed widely in China, but with difficulties for decomposition and utilization due to the complexity of its fibrous cell walls. To detect whether M. sinensis could increase the population of rumen fibrolitic microbes, two16S rRNA gene libraries were constructed using ruminal samples from Xiangxi yellow cattle fed with either common mixed feedstuff (group C) or M. sinensis (group M), and the diversity of ruminal bacteria and archaea in the rumens of cattle of both groups was identified. Based on the comparative analysis of these two groups, the microbial composition in group C/M was found to be: Bacteroidetes (16.33 %/28.15 %), Firmicutes (68.88 %/60.92 %), Proteobacteria (10.71 %/3.78 %), Planctomycetes (0/0.84 %), Lentisphaerae (0/0.42 %), Spirochaetes (1.02 %/0) in the Bacteria domain and Thermoplasmata (13.09 %/46.67 %), Methanomicrobia (57.14 %/12.22 %) and uncultured archaea (29.76 %/41.11 %) in the Archaea domain, respectively. Moreover, through phylogenetic analysis, we also detected the increase of Bacteroidetes and the decrease of Methanomicrobia in group M. These results indicated that feeding cattle with M. sinensis will change the microbial composition in the rumen; the increased bacteroidetes may be responsible for digesting M. sinensis, which will benefit us in further screening for potentially valuable bio-enzymes.     

Bacterial iron detoxification at the molecular level

Iron is an essential micronutrient, and, in the case of bacteria, its availability is commonly a growth-limiting factor. However, correct functioning of cells requires that the labile pool of chelatable “free” iron be tightly regulated. Correct metalation of proteins requiring iron as a cofactor demands that such a readily accessible source of iron exist, but overaccumulation results in an oxidative burden that, if unchecked, would lead to cell death. The toxicity of iron stems from its potential to catalyze formation of reactive oxygen species that, in addition to causing damage to biological molecules, can also lead to the formation of reactive nitrogen species. To avoid iron-mediated oxidative stress, bacteria utilize iron-dependent global regulators to sense the iron status of the cell and regulate the expression of proteins involved in the acquisition, storage, and efflux of iron accordingly. Here, we survey the current understanding of the structure and mechanism of the important members of each of these classes of protein. Diversity in the details of iron homeostasis mechanisms reflect the differing nutritional stresses resulting from the wide variety of ecological niches that bacteria inhabit. However, in this review, we seek to highlight the similarities of iron homeostasis between different bacteria, while acknowledging important variations. In this way, we hope to illustrate how bacteria have evolved common approaches to overcome the dual problems of the insolubility and potential toxicity of iron.     

Mapping Quantitative Trait Loci for Omega-3 Fatty Acids in Asian Seabass

Omega-3 fatty acids are essential fatty acids for human health. Therefore, increasing both percentage of omega-3 and a better fatty acid profile in fish fillets is one of the breeding goals in aquaculture. However, it is difficult to increase the omega-3 content in fish fillets, as the phenotypic selection of these traits is not easily feasible. To facilitate the genetic improvement of the Asian seabass for optimal fatty acid profiles, a genome-wide scan for quantitative trait loci (QTL) affecting fatty acid level in the flesh of the Asian seabass was performed on an F₂ family containing 314 offspring. All family members were genotyped using 123 informative microsatellites and 22 SNPs. High percentages of n-3 polyunsaturated fatty acids (PUFA), especially C22:6 (DHA 16.48?±?3.09 %) and C20:5 (EPA 7.19?±?0.86 %) were detected in the flesh. One significant and 54 suggestive QTL for different fatty acids and a water content trait were detected on the whole genome. QTL for C18:0b was located on linkage groups (LG) 5. QTL for total n-3 PUFA content in flesh were mapped onto LG6 and LG23 with the phenotypic variance explained ranging from 3.8 to 6.3 %. Four QTL for C22:6 were detected on LG6, LG23, and LG24, explaining 3.9 to 4.9 % of the phenotypic variance, respectively. Mapping of QTL for contents of different fatty acids is the first step towards improving the omega-3 content in the fillets of fish by using marker-assisted selection and is important for understanding the biology of fatty acid deposition.     

Comparative EPR studies on the nitrite reductases from Escherichia coli and Wolinella succinogenes

Hexaheme nitrite reductases purified to homogeneity from Escherichia coli K-12 and Wolinella succinogenes were studied by low-temperature EPR spectroscopy. In their isolated states, the two enzymes revealed nearly identical EPR spectra when measured at 12 K. Both high-spin and low-spin ferric heme EPR resonances with g values of 9.7, 3.7, 2.9, 2.3 and 1.5 were observed. These signals disappeared upon reduction by dithionite. Reaction of reduced enzyme with nitrite resulted in the formation of ferrous heme-NO complexes with distinct EPR spectral characteristics. The heme-NO complexes formed with the two enzymes differed, however, in g values and line-shapes. When reacted with hydroxylamine, reduced enzymes also showed the formation of ferrous heme-NO complexes. These results suggested the involvement of an enzyme-bound NO intermediate during the six-electron reduction of nitrite to ammonia catalyzed by these two hexaheme nitrite reductases. Heme proteins that can either expose bound NO to reduction or release it are significant components of both assimilatory and dissimilatory metabolisms of nitrate. The different ferrous heme-NO complexes detected for the two enzymes indicated, nevertheless, their subtle variation in heme reactivity during the reduction reaction.     

Circumferential analysis of digitalized gamma angiocardiography by assessment of regional left ventricular contraction

After acquisition of a digital equilibrium gamma-angiocardiographie, circumferential analysis of end-diastolic and end-systolic frames gives 120 points diastolic and systolic curves. Their difference represents systolic volume and leads to regional left ventricular ejection fraction assessment at the considered radius level. The circumferential analysis evolute gives the regional left ventricular ejection fraction representative curves which allows especially differential diagnosis between left ventricular akinesia and dyskinesia.