The bacterial yjdF riboswitch regulates translation through its tRNA-like fold

Unlike most riboswitches, which have one cognate effector, the bacterial yjdF riboswitch binds to diverse azaaromatic compounds, only a subset of which cause it to activate translation. We examined the yjdF aptamer domain by small-angle X-ray scattering and found that in the presence of activating ligands, the RNA adopts an overall shape similar to that of tRNA. Sequence analyses suggested that the yjdF aptamer is a homolog of tRNA^Lys, and that two of the conserved loops of the riboswitch are equivalent to the D-loop and T-loop of tRNA, associating to form an elbow-like tertiary interaction. Chemical probing indicated that this association is promoted by activating ligands such as chelerythrine and harmine. In its native mRNA context, activator ligands stabilize the tRNA-like fold of the yjdF aptamer, outcompeting the attenuated state in which its T-loop base pairs to the Shine–Dalgarno element of the mRNA. Moreover, we demonstrate that the liganded aptamer itself activates translation, as authentic tRNAs, when grafted into mRNA, can potently activate translation. Taken together, our data demonstrate the ability of tRNA to function as a small-molecule responsive cis regulatory element.     

Performance bonuses and the quality of primary health care delivered by family health teams in Brazil: A difference-in-differences analysis

BackgroundPay-for-performance (P4P) programmes to incentivise health providers to improve quality of care have been widely implemented globally. Despite intuitive appeal, evidence on the effectiveness of P4P is mixed, potentially due to differences in how schemes are designed. We exploited municipality variation in the design features of Brazil’s National Programme for Improving Primary Care Access and Quality (PMAQ) to examine whether performance bonuses given to family health team workers were associated with changes in the quality of care and whether the size of bonus mattered.Methods and findingsFor this quasi-experimental study, we used a difference-in-differences approach combined with matching. We compared changes over time in the quality of care delivered by family health teams between (bonus) municipalities that chose to use some or all of the PMAQ money to provide performance-related bonuses to team workers with (nonbonus) municipalities that invested the funds using traditional input-based budgets. The primary outcome was the PMAQ score, a quality of care index on a scale of 0 to 100, based on several hundred indicators (ranging from 598 to 660) of health care delivery. We did one-to-one matching of bonus municipalities to nonbonus municipalities based on baseline demographic and economic characteristics. On the matched sample, we used ordinary least squares regression to estimate the association of any bonus and size of bonus with the prepost change over time (between November 2011 and October 2015) in the PMAQ score. We performed subgroup analyses with respect to the local area income of the family health team. The matched analytical sample comprised 2,346 municipalities (1,173 nonbonus municipalities; 1,173 bonus municipalities), containing 10,275 family health teams that participated in PMAQ from the outset. Bonus municipalities were associated with a 4.6 (95% CI: 2.7 to 6.4; p < 0.001) percentage point increase in the PMAQ score compared with nonbonus municipalities. The association with quality of care increased with the size of bonus: the largest bonus group saw an improvement of 8.2 percentage points (95% CI: 6.2 to 10.2; p < 0.001) compared with the control. The subgroup analysis showed that the observed improvement in performance was most pronounced in the poorest two-fifths of localities. The limitations of the study include the potential for bias from unmeasured time-varying confounding and the fact that the PMAQ score has not been validated as a measure of quality of care.ConclusionsPerformance bonuses to family health team workers compared with traditional input-based budgets were associated with an improvement in the quality of care.

Nasser Fardousi and colleagues investigate the association between performance bonuses and the quality of primary health care delivered by family health teams in Brazil.     

Characterizing the Interaction between Root-knot Nematodes and Soil-borne Fungi which are Pathogenic to Passion Fruit (Passiflora Edulis)

For decades there have been anecdotal claims of synergistic interactions between plant-parasitic nematodes and soil-borne fungi causing decline of productivity of passion fruit (Passiflora edulis) orchards. An empirical confirmation of these disease complexes would impact disease management and plant breeding for resistance. To test those claims, we subjected passion fruit plants to single or concomitant parasitism by Meloidogyne javanica or M. incognita and Fusarium nirenbergiae or Neocosmospora sp. under controlled conditions. Non-inoculated plants served as control for the assays. The severity of shoot symptoms and variables related to plant growth, the extent of fungal lesions, and nematode reproduction were assessed to characterize the interactions. The shoot symptoms and effect on plant growth induced by the pathogens varied, but no synergy between the pathogens was observed. Moreover, the volume of tissue lesioned by the fungi was not affected by co-parasitism of the nematodes. Conversely, plant resistance to the nematodes was not affected by co-parasitism of the fungi. The interactions M. incognita-F. nirenbergiae, M. incognita-Neocosmospora sp., M. javanica-F. nirenbergiae, and M. javanica-Neocosmospora sp. were not synergistic as previously claimed, but instead neutral.     

Cucurbit Powdery Mildew: First Insights for the Identification of the Causal Agent and Screening for Resistance of Squash Genotypes (Cucurbita moschata (Duchesne ex Lam.) Duchesne ex Poir.) in Mendoza,Argentina

The cucurbit powdery mildew (CPM) caused by different fungal species is a major concern for cucurbit crops around the world. In Argentina CPM constitutes the most common and damaging disease for cucurbits, especially for squash crops (Cucurbita moschata). The present study displays initial insights into the knowledge of the disease in western Argentina, including the determination of the prevalent species causing CPM, as well as the evaluation of the resistance of squash cultivars and breeding lines. Fungal colonies were isolated from samples collected in Mendoza province, Argentina. A field trial was also performed to assess the resistance of five squash accessions, including commercial cultivars and breeding lines. The severity of CPM was analyzed and epidemiological models were built based on empirical data. The morphological determinations and analysis with specific molecular markers confirmed Podosphaera xanthi as the prevalent causal agent of CPM in Mendoza. The results od the field trial showed differences in the resistance trait among the squash accessions. The advanced breeding line BL717/1 showed promising results as source of CPM resistance for the future development of open pollinated resistant cultivars, a crucial tool for an integrative control of the disease.     

Leishmania braziliensis causing human disease in Northeast Brazil presents loci with genotypes in long-term equilibrium

BackgroundLeishmaniases are neglected tropical diseases that inflict great burden to poor areas of the globe. Intense research has aimed to identify parasite genetic signatures predictive of infection outcomes. Consistency of diagnostic tools based on these markers would greatly benefit from accurate understanding of Leishmania spp. population genetics. We explored two chromosomal loci to characterize a population of L. braziliensis causing human disease in Northeast Brazil.Methodology/Principal findingsTwo temporally distinct samples of L. braziliensis were obtained from patients attending the leishmaniasis clinic at the village of Corte de Pedra: (2008–2011) primary sample, N = 120; (1999–2001) validation sample, N = 35. Parasites were genotyped by Sanger’s sequencing of two 600 base pairs loci starting at nucleotide positions 3,074 and 425,451 of chromosomes 24 and 28, respectively. Genotypes based on haplotypes of biallelic positions in each locus were tested for several population genetic parameters as well as for geographic clustering within the region. Ample geographic overlap of genotypes at the two loci was observed as indicated by non-significant Cusick and Edward’s comparisons. No linkage disequilibrium was detected among combinations of haplotypes for both parasite samples. Homozygous and heterozygous genotypes displayed Hardy-Weinberg equilibrium (HWE) at both loci in the two samples when straight observed and expected counts were compared by Chi-square (p>0.5). However, Bayesian statistics using one million Monte-Carlo randomizations disclosed a less robust HWE for chromosome 24 genotypes, particularly in the primary sample (p = 0.04). Fixation indices (Fst) were consistently lower than 0.05 among individuals of the two samples at both tested loci, and no intra-populational structuralization could be detected using STRUCTURE software.Conclusions/SignificanceThese findings suggest that L. braziliensis can maintain stable populations in foci of human leishmaniasis and are capable of robust genetic recombination possibly due to events of sexual reproduction during the parasite’s lifecycle.     

Processing and characterization of porous structures from chitosan and starch for tissue engineering scaffolds

Natural biodegradable polymers were processed by different techniques for the production of porous structures for tissue engineering scaffolds. Potato, corn, and sweet potato starches and chitosan, as well as blends of these, were characterized and used in the experiments. The techniques used to produce the porous structures included a novel solvent-exchange phase separation technique and the well-established thermally induced phase separation method. Characterization of the open pore structures was performed by measuring pore size distribution, density, and porosity of the samples. A wide range of pore structures ranging from 1 to 400 microm were obtained. The mechanisms of pore formation are discussed for starch and chitosan scaffolds. Pore morphology in starch scaffolds seemed to be determined by the initial freezing temperature/freezing rate, whereas in chitosan scaffolds the shape and size of pores may have been determined by the processing route used. The mechanical properties of the scaffolds were assessed by indentation tests, showing that the indentation collapse strength depends on the pore geometry and the material type. Bioactivity and degradation of the potential scaffolds were assessed by immersion in simulated body fluid.     

Relationships between biological soil crusts,bacterial diversity and abundance,and ecosystem functioning: Insights from a semi‐arid Mediterranean environment

Questions: To what degree do biological soil crusts (BSCs), which are regulators of the soil surface boundary, influence associated microbial communities? Are these associations important to ecosystem functioning in a Mediterranean semi‐arid environment? Location: Gypsum outcrops near Belmonte del Tajo, Central Spain. Methods: We sampled a total of 45 (50 cm × 50 cm) plots, where we estimated the cover of every lichen and BSC‐forming lichen species. We also collected soil samples to estimate bacterial species richness and abundance, and to assess different surrogates of ecosystem functioning. We used path analysis to evaluate the relationships between the richness/abundance of above‐ and below‐ground species and ecosystem functioning. Results: We found that the greatest direct effect upon the ecosystem function matrix was that of the biological soil crust (BSC) richness matrix. A few bacterial species were sensitive to the lichen community, with a disproportionate effect of Collema crispum and Toninia sedifolia compared to their low abundance and frequency. The lichens Fulgensia subbracteata and Toninia spp. also had negative effects on bacteria, while Diploschistes diacapsis consistently affected sensitive bacteria, sometimes positively. Despite these results, very few of the BSC effects on ecosystem function could be ascribed to changes within the bacterial community. Conclusion: Our results suggest the primary importance of the richness of BSC‐forming lichens as drivers of small‐scale changes in ecosystem functioning. This study provides valuable insights on semi‐arid ecosystems where plant cover is spatially discontinuous and ecosystem function in plant interspaces is regulated largely by BSCs.     

Carbohydrates as regulatory factors on the rooting of <Emphasis Type="Italic">Eucalyptus saligna</Emphasis> Smith and <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> Labill

Comparisons between related species with different rooting capacities can provide insights into the mechanisms controlling adventitious root development. The availability of carbohydrates is often considered exclusively as an energetic requirement to drive root development; the major regulatory role in the process is often attributed to phytohormones, particularly auxin. The roles of light quantity (irradiance) and carbohydrate supply available to young aseptic donor-plants on the adventitious rooting response of Eucalyptus globulus (rooting recalcitrant) and Eucalyptus saligna (easy-to-root) were examined. The effects of the type of carbohydrate supply (sucrose or glucose) on the rooting response of cuttings was also evaluated. Light intensity supplied to mother-plants (30 or 60 mol m^–2 s^–1) had limited influence on the rooting response of both species, whereas dark periods were detrimental, particularly for E. globulus. In E. globulus, rooting was promoted by the absence of sucrose in donor-plant media. Presence of sucrose in donor plant medium promoted root number but did not affect rooting percentage of E. saligna. A positive effect of glucose on cutting rhizogenesis was found if this hexose was supplied during the root induction phase, followed by sucrose in the root formation step, especially for E. globulus. The same effect was not seen with fructose. The beneficial effect of glucose in the induction phase on root number was also evident under suboptimal auxin concentrations.     

A ubiquitous beta-tubulin disrupts microtubule assembly and inhibits cell proliferation

Vertebrate tubulin is encoded by a multigene family that produces distinct gene products, or isotypes, of both the alpha- and beta-tubulin subunits. The isotype sequences are conserved across species supporting the hypothesis that different isotypes subserve different functions. To date, however, most studies have demonstrated that tubulin isotypes are freely interchangeable and coassemble into all classes of microtubules. We now report that, in contrast to other isotypes, overexpression of a mouse class V beta-tubulin cDNA in mammalian cells produces a strong, dose-dependent disruption of microtubule organization, increased microtubule fragmentation, and a concomitant reduction in cellular microtubule polymer levels. These changes also disrupt mitotic spindle assembly and block cell proliferation. Consistent with diminished microtubule assembly, there is an increased tolerance for the microtubule stabilizing drug, paclitaxel, which is able to reverse many of the effects of class V beta-tubulin overexpression. Moreover, transfected cells selected in paclitaxel exhibit increased expression of class V beta-tubulin, indicating that this isotype is responsible for the drug resistance. The results show that class V beta-tubulin is functionally distinct from other tubulin isotypes and imparts unique properties on the microtubules into which it incorporates.     

Cultivating <Emphasis Type="Italic">in vitro</Emphasis> coconut palms (<Emphasis Type="Italic">Cocos nucifera</Emphasis>) under glasshouse conditions with natural light,improves <Emphasis Type="Italic">in vitro</Emphasis> photosynthesis nursery survival and growth

Plantlets of coconut were cultured in vitro under three different ambient conditions including a standard culture room, a culture room inside a glasshouse with natural light but controlled temperature, and a standard glasshouse with natural light and natural fluctuations of temperature. Plantlets from the 3 treatments were compared in terms of growth, plant survival as well as net photosynthesis and efficiency of PSII (Fv/Fm ratio) both at the end of the in vitro stage and at 3 stages of ex vitro acclimatization. At the end of the in vitro stage, plantlets cultured in vitro under glasshouse conditions showed the best performance showing the highest photosynthesis rate, dry weight and number of leaves. Plantlets from the standard culture room showed the lowest photosynthesis and growth rate. After 6 months of ex vitro acclimatization, plantlets originally grown in vitro under glasshouse conditions maintained better field survival and growth rates in terms of fresh weight, dry weight and leaf number than plantlets originally grown in vitro in the standard culture room. Although more studies are required to define the reason for this effect, it is clear that the conditions of standard culture rooms are not the best for in vitro cultivation of coconut and perhaps other tropical species.