Water deficit tolerance in sugarcane is dependent on the accumulation of sugar in the leaf

Sugarcane productivity is severely affected by the occurrence of water deficit in the field, causing inhibition of growth and sugar production. Evaluating physiological responses of sugarcane under water deficit conditions is essential to understand physiological variables responsible for reaching homeostasis. Therefore, we analysed physiological traits of two sugarcane genotypes, RB835486 (Tolerant) and RB855453 (Susceptible), under water deficit conditions: well-watered (WW-Control), water deficit (WD) and rewatered (RW). The physiological response was evaluated using linear regression and multivariate analysis. Some characteristics such as water potential in leaves, photosynthesis, chlorophyll fluorescence, chlorophyll index, sucrose and starch contents did not show differences between the genotypes under water deficit conditions. However, the tolerant genotype showed increased reducing sugars content in the leaves, whereas the susceptible genotype had increased non-photochemical quenching (qN). After rewatering, the susceptible sugarcane genotype showed higher electron transport rate (ETR) and efficiency of PSII (Y). Multivariate analysis revealed that non-photochemical quenching and reducing sugars in the leaves were physiological variables responsible for reaching homestasis under water deficit conditions. Therefore, the reducing sugars concentration should be considered a physiological variable responsible for the adjustment made by the tolerant sugarcane genotype when submitted to water deficit.     

Assessment of systematic effects of methodological characteristics on candidate genetic associations

Candidate genetic association studies have been found to have a low replication rate in the past. Here, we aimed to assess whether aspects of reported methodological characteristics in genetic association studies may be related to the magnitude of effects observed. An observational, literature-based investigation of 511 case–control studies of genetic association studies indexed in 2007, was undertaken. Meta-regression analyses were used to assess the relationship between 23 reported methodological characteristics and the magnitude of genetic associations. The 511 studies had been conducted in 52 countries and were published in 220 journals (median impact factor 5.1). The multivariate meta-regression model of methodological characteristics plus disease category accounted for 17.2 % of the between-study variance in the magnitude of the reported genetic associations. Our findings are consistent with the view that better conducted and better reported genetic association research may lead to less inflated results.     

Ethylenedioxy-PIP2 Oxalate Reduces Ganglioside Storage in Juvenile Sandhoff Disease Mice

Sandhoff disease is an incurable neurodegenerative disorder caused by mutations in the lysosomal hydrolase β-hexosaminidase. Deficiency in this enzyme leads to excessive accumulation of ganglioside GM2 and its asialo derivative, GA2, in brain and visceral tissues. Small molecule inhibitors of ceramide-specific glucosyltransferase, the first committed step in ganglioside biosynthesis, reduce storage of GM2 and GA2. Limited brain access or adverse effects have hampered the therapeutic efficacy of the clinically approved substrate reduction molecules, eliglustat tartrate and the imino sugar NB-DNJ (Miglustat). The novel eliglustat tartrate analog, 2-(2,3-dihydro-1H-inden-2-yl)-N-((1R,2R)-1-(2,3-dihydrobenzo[b][1, 4]dioxin-6-yl)-1-hydroxy-3-(pyrrolidin-1-yl)propan-2-yl)acetamide (EtDO-PIP2, CCG-203586 or “3h”), was recently reported to reduce glucosylceramide in murine brain. Here we assessed the therapeutic efficacy of 3h in juvenile Sandhoff (Hexb?/?) mice. Sandhoff mice received intraperitoneal injections of phosphate buffered saline (PBS) or 3h (60 mg/kg/day) from postnatal day 9 (p-9) to postnatal day 15 (p-15). Brain weight and brain water content was similar in 3h and PBS-treated mice. 3h significantly reduced total ganglioside sialic acid, GM2, and GA2 content in cerebrum, cerebellum and liver of Sandhoff mice. Data from the liver showed that 3h reduced the key upstream ganglioside precursor (glucosylceramide), providing evidence for an on target mechanism of action. No significant differences were seen in the distribution of cholesterol or of neutral and acidic phospholipids. These data suggest that 3h can be an effective alternative to existing substrate reduction molecules for ganglioside storage diseases.     

Shifts in Antarctic megabenthic structure after ice-shelf disintegration in the Larsen area east of the Antarctic Peninsula

The aim of this study was to contribute to a general understanding of the response of the Antarctic macrobenthos to environmental variability and climate-induced changes. The change in population size of selected macrobenthic organisms was investigated in the Larsen A area east of the Antarctic Peninsula in 2007 and 2011 using ROV-based imaging methods. The results were complemented by data from the Larsen B collected in 2007 to allow a conceptual reconstruction of the environment-driven changes before the period of investigation. Both Larsen areas are characterised by ice-shelf disintegration in 1995 and 2002, respectively, as well as high inter-annual variability in sea-ice cover and oceanographic conditions. In 2007 one ascidian species, Molgula pedunculata, was abundant north and south of the stripe of remaining ice shelf between Larsen A and B. Population densities decreased drastically in the Larsen A between 2007 and 2011, coincident with the decrease in Corella eumyota, another ascidian. Among the ophiuroids, the population of deposit feeders increased, while suspension feeders halved their abundance. Current measurements indicated a northward flow between the Larsen B and Larsen A, suggesting that a major physical forcing on benthic population development comes from the South. The results demonstrate that Antarctic macrobenthic populations can exhibit dramatic population dynamics. Analyses of sea-ice dynamics, salinity, temperature and surprisingly ice-shelf disintegration history, however, did not provide any clear evidence for environmental drivers underlying the apparent changes.     

Multi-environment analysis and improved mapping of a yield-related QTL on chromosome 3B of wheat

Improved mapping, multi-environment quantitative trait loci (QTL) analysis and dissection of allelic effects were used to define a QTL associated with grain yield, thousand grain weight and early vigour on chromosome 3BL of bread wheat (Triticum aestivum L.) under abiotic stresses. The QTL had pleiotropic effects and showed QTL x environment interactions across 21 diverse environments in Australia and Mexico. The occurrence and the severity of water deficit combined with high temperatures during the growing season affected the responsiveness of this QTL, resulting in a reversal in the direction of allelic effects. The influence of this QTL can be substantial, with the allele from one parent (RAC875) increasing grain yield by up to 12.5 % (particularly in environments where both heat and drought stress occurred) and the allele from the other parent (Kukri) increasing grain yield by up to 9 % in favourable environments. With the application of additional markers and the genotyping of additional recombinant inbred lines, the genetic map in the QTL region was refined to provide a basis for future positional cloning.     

Isolation of sulfate‐reducing bacteria from deep sediment layers of the pacific ocean

Bacterial populations exist at great depths in marine sediments, but little is known about the type and characteristics of organisms in this unique bacterial environment. Cascadia Margin sediments from the Pacific Ocean have deep bacterial activity and bacterial populations, which are stimulated around a gas hydrate zone (215–225 m below sea floor [mbsf]). Bacterial sulfate reduction is the dominant anaerobic process within these sediments, and the depth distribution of sulfate‐reducing activity corresponds with distributions of viable sulfate‐reducing bacteria (SRB). Anaerobically stored sediments from this site were used to isolate sulfate‐reducing bacteria using a temperature‐gradient system, elevated pressure and temperatures, different media, and a range of growth substrates. A variety of enrichments on lactate were obtained from 0.5 and 222 mbsf, with surprisingly more rapid growth from the deeper sediments. The temperature range of enrichments producing strong growth from 222 mbsf was markedly wider than those from the near surface sediment (15–45°C and 9–19°C, respectively). This presumably reflects a temperature increase in deeper sediments. Only a few of these enrichments were successfully isolated due to very slow or no growth on subculture, despite the use of a wide range of different media and growth conditions. Psychrophilic and mesophilic sulfate‐reducing isolates were obtained from 0.5 m depth. As the minimum growth temperature of the mesophile (probably a Desulfotomaculum sp.) was above the in situ temperature of 3°C, it must have been present in the sediment as spores. A larger number of isolates (23) was obtained from 222 mbsf, and these barophilic SRB were closely related (based on 16S rRNA gene analysis), but not identical to, Desulfovibrio profundus, recently isolated from deep sediments from the Japan Sea. Bacteria related to D. profundus may be widespread in deep marine sediments.     

Biochemical Analysis of the Plasmodium falciparum Erythrocyte-binding Antigen-175 (EBA175)-Glycophorin-A Interaction: IMPLICATIONS FOR VACCINE DESIGN*?

PfEBA175 has an important role in the invasion of human erythrocytes by Plasmodium falciparum and is therefore considered a high priority blood-stage malaria vaccine candidate. PfEBA175 mediates adhesion to erythrocytes through binding of the Duffy-binding-like (DBL) domains in its extracellular domain to Neu5Acα2–3Gal displayed on the O-linked glycans of glycophorin-A (GYPA). Because of the difficulties in expressing active full-length (FL) P. falciparum proteins in a recombinant form, previous analyses of the PfEBA175-GYPA interaction have largely focused on the DBL domains alone, and therefore they have not been performed in the context of the native protein sequence. Here, we express the entire ectodomain of PfEBA175 (PfEBA175 FL) in soluble form, allowing us to compare the biochemical and immunological properties with a fragment containing only the tandem DBL domains (“region II,” PfEBA175 RII). Recombinant PfEBA175 FL bound human erythrocytes in a trypsin and neuraminidase-sensitive manner and recognized Neu5Acα2–3Gal-containing glycans, confirming its biochemical activity. A quantitative binding analysis showed that PfEBA175 FL interacted with native GYPA with a K_D ∼0.26 μm and is capable of self-association. By comparison, the RII fragment alone bound GYPA with a lower affinity demonstrating that regions outside of the DBL domains are important for interactions with GYPA; antibodies directed to these other regions also contributed to the inhibition of parasite invasion. These data demonstrate the importance of PfEBA175 regions other than the DBL domains in the interaction with GYPA and merit their inclusion in an EBA175-based vaccine.     

Insights into β-Lactamases from Burkholderia Species,Two Phylogenetically Related yet Distinct Resistance Determinants

Burkholderia cepacia complex and Burkholderia pseudomallei are opportunistic human pathogens. Resistance to β-lactams among Burkholderia spp. is attributable to expression of β-lactamases (e.g. PenA in B. cepacia complex and PenI in B. pseudomallei). Phylogenetic comparisons reveal that PenA and PenI are highly related. However, the analyses presented here reveal that PenA is an inhibitor-resistant carbapenemase, most similar to KPC-2 (the most clinically significant serine carbapenemase), whereas PenI is an extended spectrum β-lactamase. PenA hydrolyzes β-lactams with k_cat values ranging from 0.38 ± 0.04 to 460 ± 46 s⁻¹ and possesses high k_cat/k_inact values of 2000, 1500, and 75 for β-lactamase inhibitors. PenI demonstrates the highest k_cat value for cefotaxime of 9.0 ± 0.9 s⁻¹. Crystal structure determination of PenA and PenI reveals important differences that aid in understanding their contrasting phenotypes. Changes in the positioning of conserved catalytic residues (e.g. Lys-73, Ser-130, and Tyr-105) as well as altered anchoring and decreased occupancy of the deacylation water explain the lower k_cat values of PenI. The crystal structure of PenA with imipenem docked into the active site suggests why this carbapenem is hydrolyzed and the important role of Arg-220, which was functionally confirmed by mutagenesis and biochemical characterization. Conversely, the conformation of Tyr-105 hindered docking of imipenem into the active site of PenI. The structural and biochemical analyses of PenA and PenI provide key insights into the hydrolytic mechanisms of β-lactamases, which can lead to the rational design of novel agents against these pathogens.