Arabidopsis T-DNA insertional lines for CDC25 are hypersensitive to hydroxyurea but not to zeocin or salt stress

Background and Aims

In yeasts and animals, cyclin-dependent kinases are key regulators of cell cycle progression and are negatively and positively regulated by WEE1 kinase and CDC25 phosphatase, respectively. In higher plants a full-length orthologue of CDC25 has not been isolated but a shorter gene with homology only to the C-terminal catalytic domain is present. The Arabidopis thaliana;CDC25 can act as a phosphatase in vitro. Since in arabidopsis, WEE1 plays an important role in the DNA damage/DNA replication checkpoints, the role of Arath;CDC25 in conditions that induce these checkpoints or induce abiotic stress was tested.

Methods

arath;cdc25 T-DNA insertion lines, Arath;CDC25 over-expressing lines and wild type were challenged with hydroxyurea (HU) and zeocin, substances that stall DNA replication and damage DNA, respectively, together with an abiotic stressor, NaCl. A molecular and phenotypic assessment was made of all genotypes

Key Results

There was a null phenotypic response to perturbation of Arath;CDC25 expression under control conditions. However, compared with wild type, the arath;cdc25 T-DNA insertion lines were hypersensitive to HU, whereas the Arath;CDC25 over-expressing lines were relatively insensitive. In particular, the over-expressing lines consistently outgrew the T-DNA insertion lines and wild type when challenged with HU. All genotypes were equally sensitive to zeocin and NaCl.

Conclusions

Arath;CDC25 plays a role in overcoming stress imposed by HU, an agent know to induce the DNA replication checkpoint in arabidopsis. However, it could not enhance tolerance to either a zeocin treatment, known to induce DNA damage, or salinity stress.     

Antifouling activities against colonizer marine bacteria of extracts from marine invertebrates collected in the Colombian Caribbean Sea and on the Brazilian coast (Santa Catarina)

The growth inhibition of 12 native marine bacteria isolated from Aplysina sponge surfaces, the shell of a bivalve, and Phytagel immersed for 48 h in sea water were used as indicator of the antifouling activity of the extracts of 39 marine organisms (octocorals, sponges, algae, and zoanthid) collected in the Colombian Caribbean Sea and on the Brazilian coast (Santa Catarina). Gram-negative bacteria represented 75% of the isolates; identified strains belonged to Oceanobacillus iheyensis, Ochrobactrum pseudogrignonense, Vibrio campbellii, Vibrio harveyi, and Bacillus megaterium species and seven strains were classified at genus level by the 16S rRNA sequencing method. The extracts of the octocorals Pseudopterogorgia elisabethae, four Eunicea octocorals, and the sponges Topsentia ophiraphidites, Agelas citrina, Neopetrosia carbonaria, Monanchora arbuscula, Cliona tenuis, Iotrochota imminuta, and Ptilocaulis walpersii were the most active, thus suggesting those species as antifoulant producers. This is the first study of natural antifoulants from marine organisms collected on the Colombian and Brazilian coasts.     

Hypervariability of the human thyroid peroxidase gene in Italy

Using a PCR based method, we determined hypervariable markers of the Thyroid Peroxidase gene (TPO-VNTR markers) by size classification of alleles in a total of 146 blood samples (76 from Sicily and 70 from Lombardy, South and North Italy respectively). A total of 22 alleles were identified. They varied in size from 6 (0.4 Kbp) to 27 (1.5 Kbp) repeats and showed a unimodal distribution (peak at 15 repeat number). Data were compared with those previously obtained in two other Italian samples from Calabria (South Italy) and from Sardinia. Heterogeneity G tests on allele frequency distributions led to the following conclusions: 1) as observerd for the majority of the known polymorphisms, the Sardinian sample is clearly distinguishable from all the others; 2) although on the whole no significant heterogeneity emerges from the comparison between southern and northern Italians, certain allelic frequencies are able to distinguish between groups.     

New fatty acids from Colombian Caribbean Sea sponges

The fatty acid composition of whole phospholipids from marine sponges collected from the Colombian Caribbean Sea was determined as part of our studies on the order Halichondrida: Halichondria magniconulosa, Halichondria lutea, Petromica ciocalyptoides, Axinyssa ambrosia, Didiscus oxeata and Dragmaxia undata. Structure elucidation was accomplished by means of gas chromatography retention parameters and GCMS. Eight new fatty acids were identified by their methyl esters and N-acylpyrrolidide derivatives (i.e. 5-methyl-6-octadecenoic, 16-methyl-11-heptadecenoic, 8-methyl-4-tetracosenoic, 8,17-dimethyl-5-octadecenoic, 23-methyl-8-tetracosenoic, 20-methyl-18-tetracosenoic, 4,17-tetracosadienoic and 22,27-dimethyl-5,9-octacosadienoic acids). These findings establish alternative fatty acid biosynthetic possibilities for these organisms.     

Complement Receptor 1 Is a Sialic Acid-Independent Erythrocyte Receptor of Plasmodium falciparum

Plasmodium falciparum is a highly lethal malaria parasite of humans. A major portion of its life cycle is dedicated to invading and multiplying inside erythrocytes. The molecular mechanisms of erythrocyte invasion are incompletely understood. P. falciparum depends heavily on sialic acid present on glycophorins to invade erythrocytes. However, a significant proportion of laboratory and field isolates are also able to invade erythrocytes in a sialic acid-independent manner. The identity of the erythrocyte sialic acid-independent receptor has been a mystery for decades. We report here that the complement receptor 1 (CR1) is a sialic acid-independent receptor for the invasion of erythrocytes by P. falciparum. We show that soluble CR1 (sCR1) as well as polyclonal and monoclonal antibodies against CR1 inhibit sialic acid-independent invasion in a variety of laboratory strains and wild isolates, and that merozoites interact directly with CR1 on the erythrocyte surface and with sCR1-coated microspheres. Also, the invasion of neuraminidase-treated erythrocytes correlates with the level of CR1 expression. Finally, both sialic acid-independent and dependent strains invade CR1 transgenic mouse erythrocytes preferentially over wild-type erythrocytes but invasion by the latter is more sensitive to neuraminidase. These results suggest that both sialic acid-dependent and independent strains interact with CR1 in the normal red cell during the invasion process. However, only sialic acid-independent strains can do so without the presence of glycophorin sialic acid. Our results close a longstanding and important gap in the understanding of the mechanism of erythrocyte invasion by P. falciparum that will eventually make possible the development of an effective blood stage vaccine.     

Bioenergy production and sustainable development: science base for policymaking remains limited

The possibility of using bioenergy as a climate change mitigation measure has sparked a discussion of whether and how bioenergy production contributes to sustainable development. We undertook a systematic review of the scientific literature to illuminate this relationship and found a limited scientific basis for policymaking. Our results indicate that knowledge on the sustainable development impacts of bioenergy production is concentrated in a few well‐studied countries, focuses on environmental and economic impacts, and mostly relates to dedicated agricultural biomass plantations. The scope and methodological approaches in studies differ widely and only a small share of the studies sufficiently reports on context and/or baseline conditions, which makes it difficult to get a general understanding of the attribution of impacts. Nevertheless, we identified regional patterns of positive or negative impacts for all categories – environmental, economic, institutional, social and technological. In general, economic and technological impacts were more frequently reported as positive, while social and environmental impacts were more frequently reported as negative (with the exception of impacts on direct substitution of GHG emission from fossil fuel). More focused and transparent research is needed to validate these patterns and develop a strong science underpinning for establishing policies and governance agreements that prevent/mitigate negative and promote positive impacts from bioenergy production.     

Reconstituted skin from murine embryonic stem cells

Embryonic stem (ES) cell lines can be expanded indefinitely in culture while maintaining their potential to differentiate into any cell type. During embryonic development, the skin forms as a result of reciprocal interactions between mesoderm and ectoderm. Here, we report the in vitro differentiation and enrichment of keratinocytes from murine ES cells seeded on extracellular matrix (ECM) in the presence of Bone Morphogenic Protein-4 (BMP-4) or ascorbate. The enriched preparation of keratinocytes was able to form an epidermal equivalent composed of a stratified epithelium when cultured at the air-liquid interface on a collagen-coated acellular substratum. Interestingly, an underlying cellular compartment that belongs to the fibroblast lineage was systematically formed between the reconstituted epidermis and the inert membrane. The resulting tissue displayed morphological patterns similar to normal embryonic skin, as evidenced by light and transmission electron microscopy. Immunohistochemical studies revealed expression patterns of cytokeratins, basement membrane (BM) proteins and late differentiation markers of epidermis, as well as fibroblast markers, similar to native skin. The results demonstrate the capacity of ES cells to reconstitute in vitro a fully differentiated skin. This ES-derived bioengineered skin provides a powerful tool for studying the molecular mechanisms controlling epidermal and dermal commitments.