Oxygen isotope fractionation between human phosphate and water revisited

The oxygen isotope composition of human phosphatic tissues (δ¹⁸O_P) has great potential for reconstructing climate and population migration, but this technique has not been applied to early human evolution. To facilitate this application we analyzed δ¹⁸O_P values of modern human teeth collected at 12 sites located at latitudes ranging from 4°N to 70°N together with the corresponding oxygen composition of tap waters (δ¹⁸O_W) from these areas. In addition, the δ¹⁸O of some raw and boiled foods were determined and simple mass balance calculations were performed to investigate the impact of solid food consumption on the oxygen isotope composition of the total ingested water (drinking water + solid food water). The results, along with those from three, smaller published data sets, can be considered as random estimates of a unique δ¹⁸O_W/δ¹⁸O_P linear relationship: δ¹⁸O_W = 1.54(±0.09) × δ¹⁸O_P−33.72(±1.51) (R² = 0.87: p [H₀:R² = 0] = 2 × 10⁻¹⁹). The δ¹⁸O of cooked food is higher than that of the drinking water. As a consequence, in a modern diet the δ¹⁸O of ingested water is +1.05 to 1.2‰ higher than that of drinking water in the area. In meat-dominated and cereal-free diets, which may have been the diets of some of our early ancestors, the shift is a little higher and the application of the regression equation would slightly overestimate δ¹⁸O_W in these cases.     

Acquisition and Evolution of Plant Pathogenesis–Associated Gene Clusters and Candidate Determinants of Tissue-Specificity in Xanthomonas

Background

Xanthomonas is a large genus of plant-associated and plant-pathogenic bacteria. Collectively, members cause diseases on over 392 plant species. Individually, they exhibit marked host- and tissue-specificity. The determinants of this specificity are unknown.

Methodology/Principal Findings

To assess potential contributions to host- and tissue-specificity, pathogenesis-associated gene clusters were compared across genomes of eight Xanthomonas strains representing vascular or non-vascular pathogens of rice, brassicas, pepper and tomato, and citrus. The gum cluster for extracellular polysaccharide is conserved except for gumN and sequences downstream. The xcs and xps clusters for type II secretion are conserved, except in the rice pathogens, in which xcs is missing. In the otherwise conserved hrp cluster, sequences flanking the core genes for type III secretion vary with respect to insertion sequence element and putative effector gene content. Variation at the rpf (regulation of pathogenicity factors) cluster is more pronounced, though genes with established functional relevance are conserved. A cluster for synthesis of lipopolysaccharide varies highly, suggesting multiple horizontal gene transfers and reassortments, but this variation does not correlate with host- or tissue-specificity. Phylogenetic trees based on amino acid alignments of gum, xps, xcs, hrp, and rpf cluster products generally reflect strain phylogeny. However, amino acid residues at four positions correlate with tissue specificity, revealing hpaA and xpsD as candidate determinants. Examination of genome sequences of xanthomonads Xylella fastidiosa and Stenotrophomonas maltophilia revealed that the hrp, gum, and xcs clusters are recent acquisitions in the Xanthomonas lineage.

Conclusions/Significance

Our results provide insight into the ancestral Xanthomonas genome and indicate that differentiation with respect to host- and tissue-specificity involved not major modifications or wholesale exchange of clusters, but subtle changes in a small number of genes or in non-coding sequences, and/or differences outside the clusters, potentially among regulatory targets or secretory substrates.     

An alternative HPLC method for the quantification of floridoside in salt-stressed cultures of the red alga Grateloupia doryphora

The floridoside content of the marine red alga Grateloupiadoryphora was measured using a new, alternative High PerformanceLiquid Chromatography method suitable for the analysis of a large number ofsamples. This assay was to study the quantitative changes in floridosideconcentration in G. doryphora cultivated in differentsalinities for 10 days. Marked changes in floridoside concentration occurredrapidly observed in reponse to osmotic stress, providing evidence of itsosmoregulatory function. Interestingly, after a rapid decrease at low salinityand a strong increase at high salinity, the floridoside content then slowlyreturned to its initial level over the last 3 days of culture. This observationconfirms the high physiological capacity of G. doryphoratowithstand environmental variations and probably contributes to its actualproliferation along French coasts.     

Shoot regeneration capacity from roots and transgenic hairy roots of tomato cultivars and wild related species

The organogenetic competence of roots and Agrobacterium rhizogenes-induced hairy roots of twelve Lycopersicon genotypes was investigated. Both roots and hairy roots of L. peruvianum, L. chilense, L. hirsutum and two L. peruvianum-derived genotypes regenerated shoots after 2–4 weeks of incubation on zeatin-contained medium. Anatomical analysis showed that shoot regeneration in roots could be direct or indirect, depending on the genotype considered. Hairy roots showed considerable differences in their morphogenetic responses, when compared to the corresponding non-transgenic roots. The differences observed may reflect the influence of the introduced rol genes on hormonal metabolism/sensitivity. Hairy root-derived T0 plants had shortened internodes, wrinkled leaves and abundant root initiation, and most produced flowers and fruits with viable seeds. The hairy root syndrome was detected early in germinating T1 seedlings as a strong reduction in the hypocotyl length. Our data point to the possibility of the use of A. rhizogenes, combined with regenerating Lycopersicon genotypes, in a very simple protocol, based on genetic capacity instead of special procedures for regeneration, to produce transgenic tomato plants expressing rol genes, as well as, genes present in binary vectors. Furthermore, the regeneration differences observed in each Lycopersicon genotype and in transgenic materials expressing rol genes open the possibility for their use in the analysis of both the biochemical and the genetic background of organogenetic competence. This revised version was published online in June 2006 with corrections to the Cover Date.     

Potential invasion of China by exotic insect pests associated with tree seeds

A total of 39 insect species, mostly seed chalcids in the genus Megastigmus (Hymenoptera), but also midges (Diptera), are listed as potential seed-borne invaders of Chinese conifers. Although the number of native seed insects per conifer genus does not differ between China and other biogeographical regions, there are significantly fewer seed insects associated with each conifer genus in China than potential invaders. The eventual success of the invaders is likely to depend on the presence of native Chinese conifers that are congeneric with the original host, or on the presence of the original host as an exotic. When a substantial entomofauna is already associated with cones, competition for seed resources may limit the potential impact of invaders because seed insects are usually the last organisms to colonize the cone. A survey of 26 fir species, both native and introduced to Europe, showed that overall seed infestation by five species of exotic chalcids is negatively correlated to levels of damage by native insects, except on the original hosts of the chalcids. Similar patterns are hypothesized for native firs, spruces, Douglas firs, and larches in China. Uncontrolled importation of seeds and nuts of broad-leaved trees could also facilitate the introduction of seed chalcids, seed bruchids, tortricid moths and nut weevils into China. Only six species of seed chalcids are present in China, out of the 72 known to attack broad-leaved seeds over the world.     

Comparative immunohistochemical localization of fibronectin and actin in human breast tumor cells in vivo and in vitro

The presence and distribution of fibronectin and actin in breast fibroadenoma cells have been investigated in frozen sections and primocultures of the same samples, by means of indirect immunofluorescence techniques. In the tissue cells, epithelial cells were negative whereas myoepithelial cells were positive with the two antibodies. Moreover, fibronectin was mainly distributed in basal lamina of ducts and ductules whereas actin appeared to label stroma cells. In primocultures obtained from the same samples of fibroadenomas, the labelled patterns of fibronectin and actin were not really distinguishable between cells; the two protein distributions were quite usual. Our data on human breast fibroadenoma cells are in agreement with the concepts of cellular adaptation or selection in culture and emphasize the difficulty in correlating results of "in vitro" and "in vivo" studies.     

Characterization of N-methyl-L-methionine sulfoxide and isethionic acid from the red alga Grateloupia doryphora

Isethionic acid (2‐hydroxyethane sulfonic acid) and N‐methyl‐L‐methionine sulfoxide (4‐methane sulfinyl‐2‐methylamino butyric acid) were isolated from the red alga Grateloupia doryphora (Cryptonemiales) collected from Brittany (France); they were identified as major organic solutes together with floridoside (α‐D‐galacto‐pyranosyl‐(1–2)‐glycerol). The presence of isethionic acid has recently been reported in certain red algae, however, the occurrence of N‐methyl‐L‐methionine sulfoxide is still very rare. This report deals with the first isolation of isethionic acid and N‐methyl‐L‐methionine sulfoxide from G. doryphora and their subsequent NMR characterization.