Mode of action of chlorsulfuron in a sensitive wheat (Triticum aestivum) cultivar: primary and secondary effects on nitrogen assimilation

Chlorsulfuron (15 g a.i. ha^-1) inhibited growth of wheat (Triticurn aestivum L. cv. Rongotea) especially on high nitrate (NO₃) supply. Decreased growth at high NO^-₃ was associated with higher concentrations of reduced nitrogen (N) and NO^-₃ in the shoots. Seven days after spraying (DAS), shoot dry weight (dry wt) of sprayed plants was similar with NO^-₃ or branched chain amino acids as main N supply but 28 DAS, shoot dry wt was greater with the amino acid treatment. One DAS, chlorsulfuron caused substantial decreases in extension of the youngest leaf and acetolactate synthase activity and valine content of shoots of plants supplied with NO^-₃ or branched chain amino acids. Total amino acid content of shoots was greater in sprayed plants than in unsprayed plants 1 DAS. Acetolactate synthase activity of sprayed plants supplied low NO^-₃ returned to normal 14–21 DAS. For sprayed plants transferred from low to high NO^-₃ supply 7, 14 or 21 DAS, shoot dry wt 50 DAS increased with increased time of transfer to high NO^-₃ while shoot NO^-₃ content decreased. Shoot NO₃ content of sprayed plants transferred to high NO^-₃ supply 7 or 14 DAS was similar to that in unsprayed plants at applied NO^-₃ concentrations which inhibited growth. It is concluded that inhibition of acetolactate synthase is likely to be the primary mode of action of chlorsulfuron in this wheat cultivar; data are consistent with the proposal that subsequent NO^-₃ accumulation can also inhibit growth.     

In silico single strand melting curve: a new approach to identify nucleic acid polymorphisms in Totiviridae

Background

The PCR technique and its variations have been increasingly used in the clinical laboratory and recent advances in this field generated new higher resolution techniques based on nucleic acid denaturation dynamics. The principle of these new molecular tools is based on the comparison of melting profiles, after denaturation of a DNA double strand. Until now, the secondary structure of single-stranded nucleic acids has not been exploited to develop identification systems based on PCR. To test the potential of single-strand RNA denaturation as a new alternative to detect specific nucleic acid variations, sequences from viruses of the Totiviridae family were compared using a new in silico melting curve approach. This family comprises double-stranded RNA virus, with a genome constituted by two ORFs, ORF1 and ORF2, which encodes the capsid/RNA binding proteins and an RNA-dependent RNA polymerase (RdRp), respectively.

Results

A phylogenetic tree based on RdRp amino acid sequences was constructed, and eight monophyletic groups were defined. Alignments of RdRp RNA sequences from each group were screened to identify RNA regions with conserved secondary structure. One region in the second half of ORF2 was identified and individually modeled using the RNAfold tool. Afterwards, each DNA or RNA sequence was denatured in silico using the softwares MELTSIM and RNAheat that generate melting curves considering the denaturation of a double stranded DNA and single stranded RNA, respectively. The same groups identified in the RdRp phylogenetic tree were retrieved by a clustering analysis of the melting curves data obtained from RNAheat. Moreover, the same approach was used to successfully discriminate different variants of Trichomonas vaginalis virus, which was not possible by the visual comparison of the double stranded melting curves generated by MELTSIM.

Conclusion

In silico analysis indicate that ssRNA melting curves are more informative than dsDNA melting curves. Furthermore, conserved RNA structures may be determined from analysis of individuals that are phylogenetically related, and these regions may be used to support the reconstitution of their phylogenetic groups. These findings are a robust basis for the development of in vitro systems to ssRNA melting curves detection.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2105-15-243) contains supplementary material, which is available to authorized users.     

Regulation of IFN response gene activity during infliximab treatment in rheumatoid arthritis is associated with clinical response to treatment

Introduction  

Cross-regulation between TNF and type I IFN has been postulated to play an important role in autoimmune diseases. Therefore, we determined the effect of TNF blockade in rheumatoid arthritis (RA) on the type I IFN response gene activity in relation to clinical response.     

Disease-modifying antirheumatic drugs are associated with a reduced risk for cardiovascular disease in patients with rheumatoid arthritis: a case control study

Rheumatoid arthritis (RA) is characterized by inflammation and an increased risk for cardiovascular disease (CVD). This study investigates possible associations between CVD and the use of conventional disease-modifying antirheumatic drugs (DMARDs) in RA. Using a case control design, 613 RA patients (5,649 patient-years) were studied, 72 with CVD and 541 without CVD. Data on RA, CVD and drug treatment were evaluated from time of RA diagnosis up to the first cardiovascular event or the end of the follow-up period. The dataset was categorized according to DMARD use: sulfasalazine (SSZ), hydroxychloroquine (HCQ) or methotrexate (MTX). Odds ratios (ORs) for CVD, corrected for age, gender, smoking and RA duration, were calculated per DMARD group. Patients who never used SSZ, HCQ or MTX were used as a reference group. MTX treatment was associated with a significant CVD risk reduction, with ORs (95% CI): 'MTX only', 0.16 (0.04 to 0.66); 'MTX and SSZ ever', 0.20 (0.08 to 0.51); and 'MTX, SSZ and HCQ ever', 0.20 (0.08 to 0.54). The risk reductions remained significant after additional correction for the presence of rheumatoid factor and erosions. After correction for hypertension, diabetes and hypercholesterolemia, 'MTX or SSZ ever' and 'MTX, SSZ and HCQ ever' showed significant CVD risk reduction. Rheumatoid factor positivity and erosions both increased CVD risk, with ORs of 2.04 (1.02 to 4.07) and 2.36 (0.92 to 6.08), respectively. MTX and, to a lesser extent, SSZ were associated with significantly lower CVD risk compared to RA patients who never used SSZ, HCQ or MTX. We hypothesize that DMARD use, in particular MTX use, results in powerful suppression of inflammation, thereby reducing the development of atherosclerosis and subsequently clinically overt CVD.     

The effects of different external nitrate concentrations on growth of Phaseolus vulgaris cv. Seafarer at chilling temperatures

The effects of different applied nitrate concentrations (1 to 50 mol m³) on growth of Phaseolus vulgaris cv. Seafarer at temperatures around 15°C was examined. Total plant dry weight and carbon content decreased sharply with increased applied nitrate 1 to 10 mol m^-3 then decreased slightly with further increases in applied N. Total plant reduced -N content increased sharply with increased applied nitrate concentration from 1 to 5 mol m^-3, changed little with increased applied nitrate from 5 to 25 mol m^-3, then increased when applied nitrate was increased from 25 to 50 mol m^-3. Nitrate concentration in all tissues increased sharply with applied nitrate increased from 1 to 10 mol m³ and showed a further increase at 50 mol m³ applied nitrate. Fresh weight to dry weight ratio for all leaves and specific leaf area for all secondary leaves increased sharply with applied nitrate concentration from 1 to 5 mol m^-3 then decreased with applied nitrate 25 to 50 mol m³ Secondary leaf chlorophyll concentration decreased sharply when applied nitrate increased from 1 to 5 mol m^-3 but increased with applied nitrate from 25 to 50 mol m^-3. Initially, the rate of leaf extension was greater at 20 mol m^-3 applied nitrate than 1 mol m^-3 applied nitrate. It is proposed that decreased growth with increased applied nitrate in the range 1 to 10 mol m^-3 is due to increased leaf damage caused by a greater rate of leaf expansion.     

Studies of the transmissibility of the agent of bovine spongiform encephalopathy to the domestic chicken

Background

Escherichia coli O157:H7 is the most common serovar of enterohemorrhagic E. coli associated with serious human disease outbreaks. Cattle are the main reservoir with E. coli O157:H7 inducing hemorrhagic enteritis in persistent shedding beef cattle, however little is known about how this pathogen affects cattle health. Jejunal Hemorrhage Syndrome (JHS) has unclear etiology but the pathology is similar to that described for E. coli O157:H7 challenged beef cattle suggestive that E. coli O157:H7 could be involved. There are no effective treatments for JHS however new approaches to managing pathogen issues in livestock using prebiotics and probiotics are gaining support. The first objective of the current study was to characterize pathogen colonization in hemorrhaged jejunum of dairy cattle during natural JHS outbreaks. The second objective was to confirm the association of mycotoxigenic fungi in feeds with the development of JHS and also to identify the presence of potential mycotoxins. The third objective was to determine the impact of a prebiotic, Celmanax?, or probiotic, Dairyman's Choice? paste, on the cytotoxicity associated with feed extracts in vitro. The fourth objective was to determine the impact of a prebiotic or a probiotic on E. coli O157:H7 colonization of mucosal explants and a bovine colonic cell line in vitro. The final objective was to determine if prebiotic and probiotic feed additives could modify the symptoms that preceded JHS losses and the development of new JHS cases.

Findings

Dairy cattle developed JHS after consuming feed containing several types of mycotoxigenic fungi including Fusarium culmorum, F. poae, F. verticillioides, F. sporotrichioides, Aspergillus flavus, Penicillium roqueforti, P. crustosum, P. paneum and P. citrinum. Mixtures of Shiga toxin - producing Escherichia coli (STEC) colonized the mucosa in the hemorrhaged tissues of the cattle and no other pathogen was identified. The STECs expressed Stx1 and Stx2, but more significantly, Stxs were also present in the blood clot blocking the jejunum. Mycotoxin analysis of the corn crop confirmed the presence of fumonisin, NIV, ZEAR, DON, 15-ADON, 3-ADON, NEO, DAS, HT-2 and T-2. Feed extracts were toxic to enterocytes and 0.1% Celmanax? removed the cytotoxicity in vitro. There was no effect of Dairyman's Choice? paste on feed-extract activity in vitro. Fumonisin, T-2, ZEAR and DON were toxic to bovine cells and 0.1% Celmanax? removed the cytotoxicity in vitro. Celmanax? also directly decreased E. coli O157:H7 colonization of mucosal explants and a colonic cell line in a dose-dependent manner. There was no effect of Dairyman's Choice? paste on E. coli O157:H7 colonization in vitro. The inclusion of the prebiotic and probiotic in the feed was associated with a decline in disease.

Conclusion

The current study confirmed an association between mycotoxigenic fungi in the feed and the development of JHS in cattle. This association was further expanded to include mycotoxins in the feed and mixtures of STECs colonizing the severely hemorrhaged tissues. Future studies should examine the extent of involvement of the different STEC in the infection process. The prebiotic, Celmanax?, acted as an anti-adhesive for STEC colonization and a mycotoxin binder in vitro. Future studies should determine the extent of involvement of the prebiotic in altering disease.     

How Do Plants Survive Ice?

Plant species have had to adapt to freezing and the presenceof ice in many climatic zones. Annual plants avoid ice by seeddispersal but, for biennials and perennials to survive theymust cope with ice in various forms. Most plants that are regularlyexposed to ice during their life cycles have acquired a dormantor quiescent winter period, when they are more tolerant to freezingtemperatures. This Botanical Briefing explores some associationsbetween plants and ice, with an emphasis on processes in plantsthat alleviate stress imposed by ice cover. Examples are takenfrom winter cereals which must reach an equilibrium both withice and with freezing temperatures for survival and economicproductivity. Acclimation; anaerobiosis; anoxia; cold; flooding; hypoxia; ice; ice encasement; winter survival     

Thermal performance of squamate embryos with respect to climate,adult life history,and phylogeny

Reptiles are important model systems for examining the effect of temperature during development on the phenotype of individuals after hatching or birth. To assess whether squamate embryos exhibit adaptive variation in thermal biology, we derived three parameters: an index of developmental rate (DRI), the upper thermal limit for successful incubation, and the lower thermal limit for development for 28 species of lizard and 12 species of snake. The associations between developmental parameters and climatic and life‐history variables were examined using both conventional statistics and phylogenetically controlled analyses. Residual DRI (i.e. DRI corrected for stage at oviposition and hatchling mass) was strongly associated with phylogenetic relationship. By contrast, the upper limit for development was negatively related to the amount of precipitation during the warmest quarter of the year, and the lower thermal limit for development was positively related to temperature during the warmest quarter of the year and the activity body temperatures of adults. These latter observations indicate that embryonic thermal physiology is adapted to large‐scale environmental patterns, and that global climate change will impact embryonic development directly through impacts on nest temperature per se, as well as indirectly through impacts on the ability of gravid females to select suitable nest sites. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.