Diversity and ecology of algae from the Nahal Qishon river,northern Israel

In 59 samples of periphyton and phytoplankton collected in 2002 - 2003 from the Nahal Qishon (Qishon River), northern Israel, we found 178 species from seven divisions of algae and cyanoprocaryotes. Diatoms, clorophytes, and cyanoprocaryotes prevail. Nitzschia and Navicula (Bacillariophyta) are the most abundant. Most of the species are cosmopolitan or widespread, except Lagynion janei (Chrysophyta), which is endemic for the Mediterranean Realm. About 17% of species (26) are new for Israel and five of them represent the first recorded genera: Crinalium endophyticum Crow, Actinocyclus normanii (Gregory) Hustedt, Rhizoclonium hieroglyphicum (Agardh) Kütz (Chlorophyta), Lagynion janei Bourelly, and Stylococcus aureus Chodat. Most of them come from a rare riverine assemblage with red alga Audouinella pygmea, as well as from the estuarine assemblage. Alkaliphiles predominate among the indicators of acidity, with few acidophiles confined to the communities under the impact of industrial wastes. Among the indicators of salinity, most numerous are the oligohalobien-indifferents and species adapted to a moderate salinity level. The relative species richness of ecological groups and the indices of saprobity are correlated with changes in conductivity, pH, and N-nitrate concentration. Indicators of organic pollution fall in the range of betameso- to alfamesosaprobic self-purification grades. Our studies show ecological significance of the Nahal Qishon as a model for a strongly disturbed aquatic ecosystem in the coastal zone of eastern Mediterranean.     

Identification and characterisation of seed storage protein transcripts from Lupinus angustifolius

Background  

In legumes, seed storage proteins are important for the developing seedling and are an important source of protein for humans and animals. Lupinus angustifolius (L.), also known as narrow-leaf lupin (NLL) is a grain legume crop that is gaining recognition as a potential human health food as the grain is high in protein and dietary fibre, gluten-free and low in fat and starch.     

Intensive nitrogen loss over the Omani Shelf due to anammox coupled with dissimilatory nitrite reduction to ammonium

A combination of stable isotopes (¹⁵N) and molecular ecological approaches was used to investigate the vertical distribution and mechanisms of biological N₂ production along a transect from the Omani coast to the central–northeastern (NE) Arabian Sea. The Arabian Sea harbors the thickest oxygen minimum zone (OMZ) in the world''s oceans, and is considered to be a major site of oceanic nitrogen (N) loss. Short (<48 h) anoxic incubations with ¹⁵N-labeled substrates and functional gene expression analyses showed that the anammox process was highly active, whereas denitrification was hardly detectable in the OMZ over the Omani shelf at least at the time of our sampling. Anammox was coupled with dissimilatory nitrite reduction to ammonium (DNRA), resulting in the production of double-¹⁵N-labeled N₂ from ¹⁵NO₂⁻, a signal often taken as the lone evidence for denitrification in the past. Although the central–NE Arabian Sea has conventionally been regarded as the primary N-loss region, low potential N-loss rates at sporadic depths were detected at best. N-loss activities in this region likely experience high spatiotemporal variabilities as linked to the availability of organic matter. Our finding of greater N-loss associated with the more productive Omani upwelling region is consistent with results from other major OMZs. The close reliance of anammox on DNRA also highlights the need to take into account the effects of coupling N-transformations on oceanic N-loss and subsequent N-balance estimates.     

1,3-Butadiene: Biomarkers and application to risk assessment

1,3-Butadiene (BD) is a known rodent and human carcinogen that is metabolized mainly by P450 2E1 to three epoxides, 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB) and 1,2-epoxy-3,4-butanediol (EB-diol). The individual epoxides vary up to 200-fold in their mutagenic potency, with DEB being the most mutagenic metabolite. It is important to understand the internal formation of the individual epoxides to assign the relative risk for each metabolite and to understand the molecular mechanisms responsible for major species differences in carcinogenicity. We have conducted extensive exposure-biomarker studies on mice, rats and humans. Using low exposures that range from current occupational levels to human exposures from tobacco smoke has provided evidence that mice are very different from humans, with mice forming ～200 times more DEB than humans at exposures of 0.1-1.5ppm BD. While no gender differences have been noted in mice and rats for globin adducts or N-7 guanine adducts, female rats and mice had 2-3-fold higher Hprt mutations and DNA-DNA cross-links, suggesting a gender difference in DNA repair. Numerous molecular epidemiology studies have evaluated globin adducts and Hprt mutations, SCEs and chromosomal abnormalities. None of the blinded studies have shown evidence of human genotoxicity at current occupational exposures and studies of globin adducts have shown similar or lower formation of adducts in females than males. If one calculates the EB dose-equivalents for the three species, mice clearly differ from rats and humans, being ～44 and 174 times greater than rats and humans, respectively. These data provide a scientific basis for improved risk assessment of BD.     

Naphthoquinone-mediated Inhibition of Lysine Acetyltransferase KAT3B/p300, Basis for Non-toxic Inhibitor Synthesis

Hydroxynaphthoquinone-based inhibitors of the lysine acetyltransferase KAT3B (p300), such as plumbagin, are relatively toxic. Here, we report that free thiol reactivity and redox cycling properties greatly contribute to the toxicity of plumbagin. A reactive 3rd position in the naphthoquinone derivatives is essential for thiol reactivity and enhances redox cycling. Using this clue, we synthesized PTK1, harboring a methyl substitution at the 3rd position of plumbagin. This molecule loses its thiol reactivity completely and its redox cycling ability to a lesser extent. Mechanistically, non-competitive, reversible binding of the inhibitor to the lysine acetyltransferase (KAT) domain of p300 is largely responsible for the acetyltransferase inhibition. Remarkably, the modified inhibitor PTK1 was a nearly non-toxic inhibitor of p300. The present report elucidates the mechanism of acetyltransferase activity inhibition by 1,4-naphthoquinones, which involves redox cycling and nucleophilic adduct formation, and it suggests possible routes of synthesis of the non-toxic inhibitor.     

Effects of jasmonate-induced defenses in tomato on the potato aphid, Macrosiphum euphorbiae

Jasmonates such as jasmonic acid (JA) are plant‐signaling compounds that trigger induced resistance (IR) to a broad range of arthropod herbivores. JA‐dependent defenses are known to reduce the growth and survivorship of many chewing insects, but their impact on piercing–sucking insects such as aphids has not been extensively investigated. In this study, induced resistance was activated in tomato (Lycopersicon esculentum Mill) (Solanaceae) using a foliar application of synthetic JA, and control plants were treated with carrier solution. The life parameters of individual potato aphids and their progeny (Macrosiphum euphorbiae Thomas) (Hemiptera: Aphididae) were evaluated on the unsprayed leaves of plants in order to access the systemic effects of the foliar treatments. IR significantly reduced the longevity and net reproduction of adult aphids, as well as the percentage of juveniles to survive to maturity. These results indicate that JA application induces systemic defenses in tomato that have a direct negative impact on aphid survivorship. This study also examined aphid honeydew excretion, in order to evaluate the potential influence of induced resistance on aphid feeding behavior. The average honeydew production per aphid was comparable on plants with or without JA treatment, indicating that JA‐dependent defenses did not deter feeding. This suggests that the observed effects of JA on aphid survivorship were due to antibiotic rather than antixenotic factors. In addition to studying the effects of JA treatment on a tomato cultivar that is susceptible to aphids, this study also examined the effects of exogenous application of JA on tomato plants that carry the aphid resistance gene, Mi‐1.2. JA application did not significantly enhance or inhibit aphid control on resistant tomato. These findings expand our understanding of the effects of JA‐dependent defenses on piercing–sucking insects, and of the potential interactions between induced resistance and R‐gene mediated aphid resistance in tomato.     

Green and blue light photoreceptors are involved in maintenance of dormancy in imbibed annual ryegrass (Lolium rigidum) seeds

Light plays an important role in two separate processes within the seeds of Lolium rigidum (annual ryegrass). Dormant seeds of L. rigidum remain dormant when imbibed in the light, but once seeds have lost dormancy through dark-stratification, light stimulates their germination. This study characterizes the light qualities and quantities which are effective in maintenance of dormancy. Dormant seeds were stratified under narrow- and broad-waveband light to identify the potential photoreceptors involved in dormancy maintenance, and to determine whether dark-induced dormancy loss is reversible by light. Blue and green light both mediated dormancy maintenance in a far-red-independent manner. Red light resulted in dormancy maintenance only when far-red wavelengths were excluded, suggesting a redundant function of phytochrome. At low fluence rates, white light was more effective than monochromatic light, suggesting the action of multiple photoreceptors in dormancy maintenance. By contrast, nondormant seeds did not germinate unless provided with red light. These results indicate that seed dormancy maintenance is potentially mediated through the actions of blue and green light photoreceptors. Seed dormancy could thus be added to the growing list of plant responses that may be mediated by green light in a cryptochrome-independent manner.     

Potential risk of biologic pollution associated to the introduction of <i>Pinus radiata</i> in grassland areas

Afforestation is a recommended practice to mitigate global warming. However, their implementation may generate undesirable impacts, mostly if exotic species are used. Plantations of Pinus radiata D Don in Ventania (Bs. As., Argentina) soils showed notorious increments of extractable P (Pe), which could affect the dynamic of this element as well as the degree of phosphorus saturation (GSP_Bray). The objectives of this study were: i) to quantify the GSP_Bray in Mollisols afforested with P. radiata comparing the results with those coming from adjacent, natural grassland areas (base line); ii) to evaluate the potential environmental risk induced by afforestation through the identification of a change point (PC) in the GSP_Bray indicative of a phosphate leaching increment. Treatments included mature stands of P. radiata (TB) and adjacent areas with natural grassland vegetation (TP). Samples were taken at 0-15; 15-30 and 30-45 cm soil depth, and texture, pH, total organic carbon (COT), Pe, soluble reactive phosphorus (PSR), phosphorus sorption index (ISP) and GSP_Bray were determined. The results showed a significant acidification in TB and an increase in the COT stock, indicating an additional atmospheric CO₂ sequestration by the trees. The Pe and PSR values were notoriously higher in TB, and they were reflected in a significant increment in the GSP_Bray with respect to TP. The detection of a significant PC in the GSP_Bray-PSR regression indicates higher chances of phosphate leaching in the forest stands, which could reach water courses, lakes and artificial reservoirs promoting their eutrophication. Because of the potential environmental pollution risk of biologic origin derived from the afforestation with P. radiata in Mollisols areas, their inclusion in clean development practices must be reconsidered.