The generation of oxygen radicals during host plant responses to infection

Recent evidence points to significant oxygen radical production by some plant tissues in response to pathogenic challenge. These findings have proved quite controversial, in part because of an inadequate appreciation of the behaviour of oxygen radicals in biological systems. This review critically discusses the evidence to date and outlines several potential roles for oxygen species in host-pathogen interactions. The production of oxygen radicals during plant defence responses is compared to the respiratory burst of mammalian phagocytic cells

One-pot multi-reaction processes: synthesis of natural products and drug-like scaffolds

One-pot multi-reaction processes involving Overman rearrangements, metathesis cyclizations, and Diels–Alder reactions have been developed for the rapid and efficient synthesis of amino-substituted carbocyclic and heterocyclic compounds. This account describes the development and optimization of these processes, as well as their applications in the synthesis of natural products and drug-like scaffolds

The crown rot ‘deadhead’ phenomenon in durum wheat

[INTRODUCTION] Crown rot of wheat, caused by Fusarium pseudograminearum (Fp), is a serious disease threat across the Australian wheat belt, particularly in durum wheat. Control of this disease is primarily based on crop rotations and reducing inoculum, with a continued goal of producing crops with increased resistance. Plant reactions to disease are typically described using stem browning, sometimes coinciding with the production of ‘deadheads’, or stems undergoing premature senescence due to infection. The mechanism by which crown rot causes yield loss has not yet been clearly described, however evidence is emerging indicating fungal blockage of both xylem and phloem tissues (1). It would be logical to infer that ‘deadhead’ stems had more Fp biomass and greater vascular tissue colonisation, resulting in their premature death. It must, however, be demonstrated. The information gained by examining ‘deadheads’ may be applied to less extreme infections as an explanation for the physiological effects behind crown rot associated yield loss. The idea behind this experiment was to investigate the levels of colonisation of stems of durum plants exhibiting ‘deadheads’ in the field and compare these to stems of the same plants which were still living. Microscopic assessment of stem sections is also planned

Assessing spot blotch resistance in barley

This workshop will discuss the nature and stability of resistance to spot blotch (Bipolaris sorokiniana/Cochliobolus sativus) in barley, with particular emphasis on the range of international resistance sources and the types of resistance characterized to date by both molecular and pathogenicity studies. One goal is to begin developing an international differential set that can be used for characterizing fungal isolates with respect to their pathogenicity in the presence of major resistance genes. The workshop format will encourage debate of the issues based around a series of short 5-10 minute presentations

Colonization of durum wheat (Triticum turgidum L. var. durum) culms exhibiting premature senescence (dead heads) associated with Fusarium pseudograminearum crown rot

Fusarium crown rot is a significant disease of durum wheat (Triticum turgidum L. var. durum), which exhibits high levels of disease susceptibility. The most extreme symptom of crown rot is a prematurely senescing culm which typically fails to set grain. Individual crown rot-affected durum wheat plants displaying both non-senescent and prematurely senescent culms were harvested to compare visual discoloration, Fusarium pseudograminearum biomass and vascular colonization in culm sections sampled at three different heights above the crown. Field samples of EGA Bellaroi were collected at Wellcamp, Queensland, in 2011, 2012, 2013 and 2014, and of Hyperno at Narrabri, New South Wales, in 2014. Prematurely senescent culms exhibited greater visual discoloration, Fusarium pseudograminearum biomass and vascular colonization than non-senescent culms in each year they were examined. The extent of these differences varied between environments and timing of collection in each year. Vascular colonization initially occurred in xylem vessels and spread into phloem tissues as disease severity increased. The increased presence of hyphae in vascular bundles of prematurely senescing culms provides strong evidence for the hypothesis that restriction of water and nutrient movement in a diseased culm is a key factor in crown rot severity

The Effects of Fish Trap Mesh Size on Reef Fish Catch off Southeastern Florida

Catch and mesh selectivity of wire-meshed fish traps were tested for eleven different mesh sizes ranging from 13 X 13 mm (0.5 x 0.5") to 76 x 152 mm (3 X 6"). A total of 1,810 fish (757 kg) representing 85 species and 28 families were captured during 330 trap hauls off southeastern Florida from December 1986 to July 1988. Mesh size significantly affected catches. The 1.5" hexagonal mesh caught the most fish by number, weight, and value. Catches tended to decline as meshes got smaller or larger. Individual fish size increased with larger meshes. Laboratory mesh retention experiments showed relationships between mesh shape and size and individual retention for snapper (Lutjanidae), grouper (Serranidae), jack (Carangidae), porgy (Sparidae), and surgeonfish (Acanthuridae). These relationships may be used to predict the effect of mesh sizes on catch rates. Because mesh size and shape greatly influenced catchability, regulating mesh size may provide a useful basis for managing the commercial trap fishery

Post-head-emergence frost in wheat and barley: defining the problem, assessing the damage, and identifying resistance

Radiant frost is a significant production constraint to wheat (Triticum aestivum) and barley (Hordeum vulgare), particularly in regions where spring-habit cereals are grown through winter, maturing in spring. However, damage to winter-habit cereals in reproductive stages is also reported. Crops are particularly susceptible to frost once awns or spikes emerge from the protection of the flag leaf sheath. Post-head-emergence frost (PHEF) is a problem distinct from other cold-mediated production constraints. To date, useful increased PHEF resistance in cereals has not been identified. Given the renewed interest in reproductive frost damage in cereals, it is timely to review the problem. Here we update the extent and impacts of PHEF and document current management options to combat this challenge. We clarify terminology useful for discussing PHEF in relation to chilling and other freezing stresses. We discuss problems characterizing radiant frost, the environmental conditions leading to PHEF damage, and the effects of frost at different growth stages. PHEF resistant cultivars would be highly desirable, to both reduce the incidence of direct frost damage and to allow the timing of crop maturity to be managed to maximize yield potential. A framework of potential adaptation mechanisms is outlined. Clarification of these critical issues will sharpen research focus, improving opportunities to identify genetic sources for improved PHEF resistance

Segregation of glutenins in wheat × maize-derived doubled haploid wheat populations

The segregation of both high and low molecular weight glutenin subunits across 7 F1 wheat (Triticum aestivum L.) × maize (Zea mays L.) derived doubled haploid populations was examined. The F1 wheats used in each population were produced from parents of interest to Australian wheat breeding programs. The parents varied by up to 5 glutenin subunit loci. Examination of subunits individually within each population using a chi-square analysis revealed that all but 2 of the 26 pairs of alleles analysed fitted the expected 1 : 1 segregation ratio. Glutenin profiles were examined for each cross individually and all but one (Sonalika/Hartog) fitted the expected Mendelian segregation pattern. The analysis of allele distribution of the 6 glutenin loci across all 7 crosses showed all falling well within expected segregation ratios. Closer examination of parental lines and populations revealed irregularities which conflict with original assumptions and provide a valid explanation for the few segregation distortions observed. It is concluded that wheat × maize-derived doubled haploid populations represent a unbiased assortment of parental gametes on both arms of Group 1 chromosomes

A moderate increase in dietary zinc reduces DNA strand breaks in leukocytes and alters plasma proteins without changing plasma zinc concentrations.

BackgroundFood fortification has been recommended to improve a population's micronutrient status. Biofortification techniques modestly elevate the zinc content of cereals, but few studies have reported a positive impact on functional indicators of zinc status.ObjectiveWe determined the impact of a modest increase in dietary zinc that was similar to that provided by biofortification programs on whole-body and cellular indicators of zinc status.DesignEighteen men participated in a 6-wk controlled consumption study of a low-zinc, rice-based diet. The diet contained 6 mg Zn/d for 2 wk and was followed by 10 mg Zn/d for 4 wk. To reduce zinc absorption, phytate was added to the diet during the initial period. Indicators of zinc homeostasis, including total absorbed zinc (TAZ), the exchangeable zinc pool (EZP), plasma and cellular zinc concentrations, zinc transporter gene expression, and other metabolic indicators (i.e., DNA damage, inflammation, and oxidative stress), were measured before and after each dietary-zinc period.ResultsTAZ increased with increased dietary zinc, but plasma zinc concentrations and EZP size were unchanged. Erythrocyte and leukocyte zinc concentrations and zinc transporter expressions were not altered. However, leukocyte DNA strand breaks decreased with increased dietary zinc, and the level of proteins involved in DNA repair and antioxidant and immune functions were restored after the dietary-zinc increase.ConclusionsA moderate 4-mg/d increase in dietary zinc, similar to that which would be expected from zinc-biofortified crops, improves zinc absorption but does not alter plasma zinc. The repair of DNA strand breaks improves, as do serum protein concentrations that are associated with the DNA repair process. This trial was registered at clinicaltrials.gov as NCT02861352

What has preclinical systematic review ever done for us?

Systematic review and meta-analysis are a gift to the modern researcher, delivering a crystallised understanding of the existing research data in any given space. This can include whether candidate drugs are likely to work or not and which are better than others, whether our models of disease have predictive value and how this might be improved and also how these all interact with disease pathophysiology. Grappling with the literature needed for such analyses is becoming increasingly difficult as the number of publications grows. However, narrowing the focus of a review to reduce workload runs the risk of diminishing the generalisability of conclusions drawn from such increasingly specific analyses. Moreover, at the same time as we gain greater insight into our topic, we also discover more about the flaws that undermine much scientific research. Systematic review and meta-analysis have also shown that the quality of much preclinical research is inadequate. Systematic review has helped reveal the extent of selection bias, performance bias, detection bias, attrition bias and low statistical power, raising questions about the validity of many preclinical research studies. This is perhaps the greatest virtue of systematic review and meta-analysis, the knowledge generated ultimately helps shed light on the limitations of existing research practice, and in doing so, helps bring reform and rigour to research across the sciences. In this commentary, we explore the lessons that we have identified through the lens of preclinical systematic review and meta-analysis