Beginning to understand the role of sugar carriers in Colletotrichum lindemuthianum: the function of the gene mfs1

Fungi of the Colletotrichum genus are among the most prominent phytopathogens that cause diseases with a considerable economic impact, such as anthracnose. The hemibiotrophic fungus Colletotrichum lindemuthianum (teleomorph Glomerella cingulata f. sp. phaseoli) is the causal agent of the anthracnose of the common bean; and similarly to other phytopathogens, it uses multiple strategies to gain access to different carbon sources from its host. In this study, we examine mfs1, a newly identified C. lindemuthianum hexose transporter. The mfs1 gene is expressed only during the necrotrophic phase of the fungus’ interaction within the plant and allows it to utilize the available sugars during this phase. The deletion of mfs1 gene resulted in differential growth of the fungus in a medium that contained glucose, mannose or fructose as the only carbon source. This study is the first to describe a hexose transporter in the hemibiotrophic pathogen C. lindemuthianum and to demonstrate the central role of this protein in capturing carbon sources during the necrotrophic development of the plant/pathogen interaction.     

Volumetric-modulated arc therapy with RapidArc®: An evaluation of treatment delivery efficiency

Aim/background

To evaluate how the use of volumetric-modulated arc therapy (VMAT) with RapidArc^® can improve treatment delivery efficiency based on the analysis of the beam-on times and monitor units (MU) needed to deliver therapy for multiple clinical applications in a large patient population.

Materials and methods

A total of 898 treatment courses were delivered in 745 patients treated from October 2008 to March 2013 using RapidArc® treatment plans generated in Eclipse™ TPS. All patients were treated with curative or palliative intent using different techniques including conventional fractionation (83%) and radiosurgery or SBRT (17%), depending on the clinical indications. Treatment delivery was evaluated based on measured beam-on time and recorded MU values delivered on a Varian Trilogy™ linear accelerator.

Results

For conventional fractionation treatments using RapidArc®, the delivery times ranged from 38 s to 4 min and 40 s (average 2 min and 6 s). For radiosurgical treatments the delivery times ranged from 1 min and 42 s to 9 min and 22 s (average 4 min and 4 s). The average number of MU per Gy was 301 for the entire group, with 285 for the conventional group and 317 for the radiosurgical group.

Conclusions

In this study with a large heterogeneous population, treatments using RapidArc® were delivered with substantially less beam-on time and fewer MUs than conventional fractionation. This was highly advantageous, increasing flexibility of the scheduling allowing treatment of radiosurgery patients during the regular daily work schedule. Additionally, reduction of leakage radiation dose was achieved.     

Use of a Base-Labile Protected Derivative of 6-Mercaptohexanol for the Preparation of Oligonucleotides Containing a Thiol Group at the 5′-End

Abstract

The preparation of a base-labile (Dnpe) protected derivative of 6-mercaptohexanol is described. The use of the phosphoramidite derivative of this compound improves both yields and the time needed for the preparation of oligonucleotides containing a thiol group at the 5′-end.     

EPR detection of paramagnetic chromium in liver of fish (Anguilla anguilla) treated with dichromate(VI) and associated oxidative stress responses—Contribution to elucidation of toxicity mechanisms

The impact of chromium (Cr) on fish health has been the subject of numerous investigations, establishing a wide spectrum of toxicity, attributed particularly to the hexavalent form [Cr(VI)]. However, reports on the simultaneous assessment of Cr toxicity in fish and its toxico-kinetics, namely involving metal speciation, are scarce. Therefore, keeping in view the understanding of the mechanisms of Cr(VI) toxicity, this work intended to detect the formation of paramagnetic Cr species in liver of Anguilla anguilla following short-term dichromate(VI) intraperitoneal treatment (up to 180 min), assessing simultaneously the pro-oxidant properties. The formation of Cr(V) and Cr(III) was examined by electron paramagnetic resonance (EPR), as an innovative approach in the context of fish toxicology, and related with the levels of total Cr. Cr(V) was successfully detected and quantified by EPR spectrometry, showing a transient occurrence, mostly between 15 and 90 min post-injection, with a peak at 30 min. The limitations of EPR methodology towards the detection and quantification of Cr(III) were confirmed. Although Cr(VI) exposure induced the antioxidant system in the eel's liver, the oxidative deterioration of lipids was not prevented. Overall, the results suggested that Cr(V), as a short-lived species, did not appear to be directly and primarily responsible for the cellular damaging effects observed, since stress responses persisted up to the end of exposure regardless Cr(V) drastic decay. Though further research is needed, ROS mediated pathways (suggested by superoxide dismutase and catalase activity induction) and formation of Cr(III) complexes emerged as the most plausible mechanisms involved in Cr(VI) toxicity.     

Growth and temperature‐related phenotypic plasticity in the cyanobacterium Cylindrospermopsis raciborskii

Cylindrospermopsis raciborskii is an invasive and potentially toxic cyanobacterium, which has recently spread worldwide, mainly because of its tolerance to a wide range of climatic conditions. C. raciborskii is able to change several traits in response to environmental changes and its morphology is also affected by these changes (especially in nutrients). We also expected temperature to affect the morphology of this cyanobacterium. We examined the growth and morphology of C. raciborskii at different temperatures and compared laboratory results to the morphology of this cyanobacterium in situ. As expected, growth rates increased with temperature. In addition, a high carrying capacity at 32°C suggests that this cyanobacterium is able to form more dense blooms at high temperatures. Fragile trichomes and low growth rates were observed at 12°C. An increase in the growth rate related to temperature resulted in a decrease in trichome length, with shorter trichomes at 32°C. The same pattern was observed in wild populations of C. raciborskii in a tropical reservoir, where shorter trichomes were observed in warmer months, when biomass was highest. This species' high ability to adapt to different environmental conditions throughout the year (i.e., nutrients, temperature) may have provided it with an additional advantage to increase its perennial blooms, mainly in tropical regions.     

Mantel test in population genetics

The comparison of genetic divergence or genetic distances, estimated by pairwise F_ST and related statistics, with geographical distances by Mantel test is one of the most popular approaches to evaluate spatial processes driving population structure. There have been, however, recent criticisms and discussions on the statistical performance of the Mantel test. Simultaneously, alternative frameworks for data analyses are being proposed. Here, we review the Mantel test and its variations, including Mantel correlograms and partial correlations and regressions. For illustrative purposes, we studied spatial genetic divergence among 25 populations of Dipteryx alata (“Baru”), a tree species endemic to the Cerrado, the Brazilian savannas, based on 8 microsatellite loci. We also applied alternative methods to analyze spatial patterns in this dataset, especially a multivariate generalization of Spatial Eigenfunction Analysis based on redundancy analysis. The different approaches resulted in similar estimates of the magnitude of spatial structure in the genetic data. Furthermore, the results were expected based on previous knowledge of the ecological and evolutionary processes underlying genetic variation in this species. Our review shows that a careful application and interpretation of Mantel tests, especially Mantel correlograms, can overcome some potential statistical problems and provide a simple and useful tool for multivariate analysis of spatial patterns of genetic divergence.     

Atlantic moonfishes: independent pathways of karyotypic and morphological differentiation

Fish of the genus Selene, known as lookdowns or moonfish, are one of the most morphologically derived groups of the family Carangidae, whose phylogenetic relationships are still largely unknown. In this study, we discuss karyoevolutionary aspects of three representatives of this genus from the Western Atlantic: Selene brownii (2n = 48; FN = 48), Selene setapinnis (2n = 46; FN = 48), and Selene vomer (2n = 48; FN = 50). Their body patterns were also investigated and compared to one another and in relation to two other species of different genera. Two mechanisms of karyotypic evolution seem to have acted in the diversification of this genus, namely pericentric inversions and centric fusions. Mapping of rDNA sequences showed that chromosome pairs bearing 5S rDNA sites are similar, whereas those bearing 18 rDNA sites are morphologically distinct while apparently also exhibiting interspecies synteny. Although the nucleolar organizer-bearing chromosomes are extremely efficient cytotaxonomic markers among Selene species, others cytogenetic patterns of these species are relatively conserved. Hybridization with telomeric probes (TTAGGG)_n did not exhibit interstitial telomeric sites (ITS), especially in S. setapinnis, where, along with a reduction in diploid number, a large metacentric pair derived from centric fusion is present. Data obtained by geometric morphometrics enable a clear morphological distinction among the three species, as well as in relation to two other species of the genus Caranx and Oligoplites. Data obtained suggest that morphologic evolution in Selene species was primarily dissociated from visible changes that occurred at the chromosomal level.     

A highly conserved mycobacterial cholesterol catabolic pathway

Degradation of the cholesterol side‐chain in Mycobacterium tuberculosis is initiated by two cytochromes P450, CYP125A1 and CYP142A1, that sequentially oxidize C26 to the alcohol, aldehyde and acid metabolites. Here we report characterization of the homologous enzymes CYP125A3 and CYP142A2 from Mycobacterium smegmatis mc² 155. Heterologously expressed, purified CYP125A3 and CYP142A2 bound cholesterol, 4‐cholesten‐3‐one, and antifungal azole drugs. CYP125A3 or CYP142A2 reconstituted with spinach ferredoxin and ferredoxin reductase efficiently hydroxylated 4‐cholesten‐3‐one to the C‐26 alcohol and subsequently to the acid. The X‐ray structures of both substrate‐free CYP125A3 and CYP142A2 and of cholest‐4‐en‐3‐one‐bound CYP142A2 reveal significant differences in the substrate binding sites compared with the homologous M. tuberculosis proteins. Deletion only of cyp125A3 causes a reduction of both the alcohol and acid metabolites and a strong induction of cyp142 at the mRNA and protein levels, indicating that CYP142A2 serves as a functionally redundant back up enzyme for CYP125A3. In contrast to M. tuberculosis, the M. smegmatis Δcyp125Δcyp142 double mutant retains its ability to grow on cholesterol albeit with a diminished capacity, indicating an additional level of redundancy within its genome.