Sequence‐level comparative analysis of the Brassica napus genome around two stearoyl‐ACP desaturase loci

We conducted a sequence‐level comparative analyses, at the scale of complete bacterial artificial chromosome (BAC) clones, between the genome of the most economically important Brassica species, Brassica napus (oilseed rape), and those of Brassica rapa, the genome of which is currently being sequenced, and Arabidopsis thaliana. We constructed a new B. napus BAC library and identified and sequenced clones that contain homoeologous regions of the genome including stearoyl‐ACP desaturase‐encoding genes. We sequenced the orthologous region of the genome of B. rapa and conducted comparative analyses between the Brassica sequences and those of the orthologous region of the genome of A. thaliana. The proportion of genes conserved (～56%) is lower than has been reported previously between A. thaliana and Brassica (～66%). The gene models for sets of conserved genes were used to determine the extent of nucleotide conservation of coding regions. This was found to be 84.2 ± 3.9% and 85.8 ± 3.7% between the B. napus A and C genomes, respectively, and that of A. thaliana, which is consistent with previous results for other Brassica species, and 97.5 ± 3.1% between the B. napus A genome and B. rapa, and 93.1 ± 4.9% between the B. napus C genome and B. rapa. The divergence of the B. napus genes from the A genome and the B. rapa genes was greater than anticipated and indicates that the A genome ancestor of the B. napus cultivar studied was relatively distantly related to the cultivar of B. rapa selected for genome sequencing.     

Differential Modulation of Angiogenesis by Erythropoiesis-Stimulating Agents in a Mouse Model of Ischaemic Retinopathy

Background

Erythropoiesis stimulating agents (ESAs) are widely used to treat anaemia but concerns exist about their potential to promote pathological angiogenesis in some clinical scenarios. In the current study we have assessed the angiogenic potential of three ESAs; epoetin delta, darbepoetin alfa and epoetin beta using in vitro and in vivo models.

Methodology/Principal Findings

The epoetins induced angiogenesis in human microvascular endothelial cells at high doses, although darbepoetin alfa was pro-angiogenic at low-doses (1–20 IU/ml). ESA-induced angiogenesis was VEGF-mediated. In a mouse model of ischaemia-induced retinopathy, all ESAs induced generation of reticulocytes but only epoetin beta exacerbated pathological (pre-retinal) neovascularisation in comparison to controls (p<0.05). Only epoetin delta induced a significant revascularisation response which enhanced normality of the vasculature (p<0.05). This was associated with mobilisation of haematopoietic stem cells and their localisation to the retinal vasculature. Darbepoetin alfa also increased the number of active microglia in the ischaemic retina relative to other ESAs (p<0.05). Darbepoetin alfa induced retinal TNFα and VEGF mRNA expression which were up to 4 fold higher than with epoetin delta (p<0.001).

Conclusions

This study has implications for treatment of patients as there are clear differences in the angiogenic potential of the different ESAs.     

A rapidly evolving secretome builds and patterns a sea shell

Background  

Instructions to fabricate mineralized structures with distinct nanoscale architectures, such as seashells and coral and vertebrate skeletons, are encoded in the genomes of a wide variety of animals. In mollusks, the mantle is responsible for the extracellular production of the shell, directing the ordered biomineralization of CaCO₃ and the deposition of architectural and color patterns. The evolutionary origins of the ability to synthesize calcified structures across various metazoan taxa remain obscure, with only a small number of protein families identified from molluskan shells. The recent sequencing of a wide range of metazoan genomes coupled with the analysis of gene expression in non-model animals has allowed us to investigate the evolution and process of biomineralization in gastropod mollusks.     

Opposing effects of estrogen and progestins on LDL oxidation and vascular wall cytotoxicity: implications for atherogenesis

Estrogens are widely regarded as beneficial to arterial wall health. Among the mechanisms of this benefit are antioxidant effects on LDL and the arterial wall. Because progestins oppose the effect of estrogen in several systems, we asked if progestins oppose the antioxidant effect of estrogen. To study this question, LDL and various female sex hormones were incubated alone and combined in the absence or presence of bovine aortic endothelial cells, placental trophoblast, or macrophages, and LDL oxidation and cytotoxicity were quantitated. In the absence of cells, LDL incubated with copper in phosphate-buffered saline enhanced the oxidation of LDL. When 17beta-estradiol was added to this system, an antioxidant effect was observed. Progestins inhibited this protective estrogenic effect. In endothelial cell culture, progestins also opposed the antioxidant effect of estrogen, with the strongest antiestrogenic effect seen with the synthetic progestins, levonorgestrel and medroxyprogesterone acetate (MPA). Endothelial cell cytotoxicity was proportional to the enhanced lipid peroxide formation observed with progestins or estrogen. Similar opposing effects were seen when estrogen and progesterone were added to primary cultures of placental trophoblast or macrophages. Thus, three cell culture systems modeling circulating arterial blood contact with cell surfaces demonstrated opposing effects of estrogens and progestins on LDL oxidation and cell cytotoxicity. These studies are in keeping with published reports that female sex steroids influence LDL oxidation in vivo and consequent arterial wall injury.     

Origin and maintenance of a broad-spectrum disease resistance locus in Arabidopsis

The broad-spectrum mildew resistance genes RPW8.1 and RPW8.2 define a unique type of plant disease resistance (R) gene, and so far homologous sequences have been found in Arabidopsis thaliana only, which suggests a recent origin. In addition to RPW8.1 and RPW8.2, the RPW8 locus contains three homologs of RPW8, HR1, HR2, and HR3, which do not contribute to powdery mildew resistance. To investigate whether RPW8 has originated recently, and if so the processes involved, we have isolated and analyzed the syntenic RPW8 loci from Arabidopsis lyrata, and from Brassica rapa and B. oleracea. The A. lyrata locus contains four genes orthologous to HR1, HR2, HR3, and RPW8.2, respectively. Two syntenic loci have been characterized in Brassica; one locus contains three genes and is present in both B. oleracea and B. rapa, and the other locus contains a single gene and is detected in B. rapa only. The Brassica homologs have highest similarity to HR3. Sequence analyses suggested that the RPW8 gene family in Brassicaceae originated from an HR3-like ancestor gene through a series of duplications and that RPW8.1 and RPW8.2 evolved from functional diversification through positive selection several MYA. Examination of the sequence polymorphism of 32 A. thaliana accessions at the RPW8 locus and their disease reaction phenotypes revealed that the polymorphic RPW8 locus defines a major source of resistance to powdery mildew diseases. A possible evolutionary mechanism by which functional polymorphism at the AtRPW8 locus has been maintained in contemporary populations of A. thaliana is discussed.     

Teratogenic actions of thermally-stressed culinary oils in rats

Lipid oxidation products (LOPs), generated in culinary oils during episodes of thermal stressing can give rise to cellular damage. The aims of this study were to determine whether orally-administered, LOP-containing thermally-stressed safflower oil exerts teratogenic actions in rats, and whether this effect could be prevented by co-administration of alpha-tocopherol (alpha-TOH). Safflower oil was heated for a period of 20 min according to standard frying practices and stored at -20 degrees C under N2. Four experimental groups of pregnant Wistar rats were employed; two received 0.30 ml of pre-heated oil (HO), one of which was also supplemented with 150 mg of alpha-TOH (HOE), and two served as controls, one treated with the non-heated oil (O) and the other without any treatment (C). The oil was administered daily by gavage from day 1 of pregnancy to day 11.5, when the animals were killed and the embryos examined. LOPs and alpha-TOH were determined both in the heated and non-heated oils. The percentage of embryo malformations and reabsorptions were determined in the above four experimental groups. Heating the oil substantially increased its concentration of LOPs and decreased its alpha-TOH content. The percentage of embryo malformations in the HO group was 21.73%, compared with 5.6 and 7% in the O and C groups, respectively. Supplementation of the pre-heated oil with alpha-TOH was found to decrease the percentage of malformations to 7%. The results obtained from these investigations indicate that LOPs detectable at millimolar levels in the heated cooking oils administered (e.g. saturated and alpha,beta-unsaturated aldehydes, and/or their conjugated hydroperoxydiene precursors) exert potent teratogenic actions in experimental animals which are at least partially circumventable by co-administration of the chain-breaking antioxidant alpha-TOH. Plausible mechanisms for these processes and their health relevance to humans regarding diet and methods of frying/cooking are discussed.