Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Rtt107/Esc4 binds silent chromatin and DNA repair proteins using different BRCT motifs

Background  

By screening a plasmid library for proteins that could cause silencing when targeted to the HMR locus in Saccharomyces cerevisiae, we previously reported the identification of Rtt107/Esc4 based on its ability to establish silent chromatin. In this study we aimed to determine the mechanism of Rtt107/Esc4 targeted silencing and also learn more about its biological functions.     

Ca2+ responses to thyrotropin-releasing hormone and angiotensin II: the role of plasma membrane integrity and effect of G11alpha protein overexpression on homologous and heterologous desensitization

The molecular mechanisms involved in GPCR-initiated signaling cascades where the two receptors share the same signaling cascade, such as thyrotropin-releasing hormone (TRH) and angiotensin II (ANG II), are still far from being understood. Here, we analyzed hormone-induced Ca(2+) responses and the process of desensitization in HEK-293 cells, which express endogenous ANG II receptors. These cells were transfected to express exogenously high levels of TRH receptors (clone E2) or both TRH receptors and G(11)alpha protein (clone E2M11). We observed that the characteristics of the Ca(2+) response, as well as the process of desensitization, were both strongly dependent on receptor number and G(11)alpha protein level. Whereas treatment of E2 cells with TRH or ANG II led to significant desensitization of the Ca(2+) response to subsequent addition of either hormone, the response was not desensitized in E2M11 cells expressing high levels of G(11)alpha. In addition, stimulation of both cell lines with THR elicited a clear heterologous desensitization to subsequent stimulation with ANG II. On the other hand, ANG II did not affect a subsequent response to TRH. ANG II-mediated signal transduction was strongly dependent on plasma membrane integrity modified by cholesterol depletion, but signaling through TRH receptors was altered only slightly under these conditions. It may be concluded that the level of expression of G-protein-coupled receptors and their cognate G-proteins strongly influences not only the magnitude of the Ca(2+) response but also the process of desensitization and resistance to subsequent hormone addition.     

Defective F pili and other characteristics of Flac and Hfr Escherichia coli mutants resistant to bacteriophage R17.

Mutants resistant to the donor-specific bacteriophage R17 were isolated from Hfr and Flac-containing strains of Escherichia coli K-12. Thirty-five mutants were examined for the presence of F pili by electron microscopy. The pilus morphology was studied, as were the abilities of the cells to retract their pili and to synthesize new pili. Measurements were made of the efficiency of the conjugal deoxyribonucleic acid transfer and of M13 and R17 phage infection. All mutants had noticeable defects in pilus production, structure, or function. Mutants were found which produced unusually long pili, displayed wide variations in the number of pili per cell, and were deficient in pilus retraction and synthesis. Evidence is presented that there may be two pathways of pilus retraction.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Association of 25-Hydroxyvitamin D status and genetic variation in the vitamin D metabolic pathway with FEV1 in the Framingham Heart Study

Background

Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.

Methods

We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV₁) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV₁ in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV₁ in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.

Results

We found a positive cross-sectional association between 25(OH)D and FEV₁ in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV₁ in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV₁ (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV₁ in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).

Conclusions

Serum 25(OH)D status was associated with cross-sectional FEV₁, but not longitudinal change in FEV₁. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV₁ and is a promising candidate gene for further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users.     

Reconstructing marine plankton food web interactions using DNA metabarcoding

Knowledge of zooplankton in situ diet is critical for accurate assessment of marine ecosystem function and structure, but due to methodological constraints, there is still a limited understanding of ecological networks in marine ecosystems. Here, we used DNA‐metabarcoding to study trophic interactions, with the aim to unveil the natural diet of zooplankton species under temporal variation of food resources. Several target consumers, including copepods and cladocerans, were investigated by sequencing 16S rRNA and 18S rRNA genes to identify prokaryote and eukaryote potential prey present in their guts. During the spring phytoplankton bloom, we found a dominance of diatom and dinoflagellate trophic links to copepods. During the summer period, zooplankton including cladocerans showed a more diverse diet dominated by cyanobacteria and heterotrophic prey. Our study suggests that copepods present trophic plasticity, changing their natural diet over seasons, and adapting their feeding strategies to the available prey spectrum, with some species being more selective. We did not find a large overlap of prey consumed by copepods and cladocerans, based on prey diversity found in their guts, suggesting that they occupy different roles in the trophic web. This study represents the first molecular approach to investigate several zooplankton–prey associations under seasonal variation, and highlights how, unlike other techniques, the diversity coverage is high when using DNA, allowing the possibility to detect a wide range of trophic interactions in plankton communities.