A Case of Occupational Rhinitis Induced by Maize Pollen Exposure in a Farmer: Detection of IgE-Binding Components

Corn is a major staple food, along with rice and wheat, in many parts of the world. There are several reports of hypersensitivity to maize pollen. However, cases of occupational allergic rhinitis induced by inhalation of maize pollen are very rare. We herein report the case of a 67-year-old male with occupational rhinitis caused by occupational exposure to maize pollen in a cornfield. He showed positive responses to maize pollen, as well as grass pollens, in skin prick tests. A high level of serum immunoglobulin E (IgE) specific to maize pollen extracts was detected by an enzyme-linked immunosorbent assay (ELISA). Laboratory tests showed a high serum level of total IgE (724 kU/L) and a high level of IgE specific to maize pollen (8.32 kU/L) using the Immuno-CAP system. Occupational rhinitis was confirmed by a nasal provocation test with maize pollen extracts. IgE ELISA inhibition tests showed antibody cross-reactivity between maize pollen and grass pollen extracts. IgE immunoblotting using maize pollen extracts demonstrated a 27 kDa IgE-binding component. These findings suggest that maize pollen can induce IgE-mediated occupational rhinitis in exposed workers.     

世界稻米、小麦、玉米加工业发展趋势与我国发展的战略

介绍了世界稻米、小麦、玉米加工业的现状与发展趋势及我国3大粮食加工业未来10年的发展目标与战略.     

An isoleucine/leucine residue in the carboxyltransferase domain of acetyl-CoA carboxylase is critical for interaction with aryloxyphenoxypropionate and cyclohexanedione inhibitors

cDNA fragments encoding the carboxyltransferase domain of the multidomain plastid acetyl-CoA carboxylase (ACCase) from herbicide-resistant maize and from herbicide-sensitive and herbicide-resistant Lolium rigidum were cloned and sequenced. A Leu residue was found in ACCases from herbicide-resistant plants at a position occupied by Ile in all ACCases from sensitive grasses studied so far. Leu is present at the equivalent position in herbicide-resistant ACCases from other eukaryotes. Chimeric ACCases containing a 1000-aa fragment of two ACCase isozymes found in a herbicide-resistant maize were expressed in a yeast ACC1 null mutant to test herbicide sensitivity of the enzyme in vivo and in vitro. One of the enzymes was resistant/tolerant, and one was sensitive to haloxyfop and sethoxydim, rendering the gene-replacement yeast strains resistant and sensitive to these compounds, respectively. The sensitive enzyme has an Ile residue, and the resistant one has a Leu residue at the putative herbicide-binding site. Additionally, a single Ile to Leu replacement at an equivalent position changes the wheat plastid ACCase from sensitive to resistant. The effect of the opposite substitution, Leu to Ile, makes Toxoplasma gondii apicoplast ACCase resistant to haloxyfop and clodinafop. In this case, inhibition of the carboxyltransferase activity of ACCase (second half-reaction) of a large fragment of the Toxoplasma enzyme expressed in Escherichia coli was tested. The critical amino acid residue is located close to a highly conserved motif of the carboxyltransferase domain, which is probably a part of the enzyme active site, providing the basis for the activity of fop and dim herbicides.     

不同枣粮间作模式物质积累及产量成因分析

在枣粮间作模式下对间作作物的物质积累及产量成因进行对比分析,以玉米品种先育335、高粱品种沈杂5号为试材,分别对其在出苗后45、60、75、90 d和105 d的净光合速率、干物质积累、产量构成因素、株高和茎粗等指标进行了测定与分析。结果表明：在枣粮间作模式下,玉米和高粱分别在ZY4和ZG8模式下粮食产量最高;高粱在各生育时期内的光合速率均高于玉米,在不同生长时期内差异较小,相对玉米可适当密植;在ZY4和ZG8的模式下玉米和高粱干物质积累平均速率高,为高产量的形成奠定物质基础;穗数和粒重受密度影响较大,穗粒数影响较小,ZY4和ZG8模式下枣树、玉米、高粱三者配置模式较好。     

Characterization of maize chitinase‐A,a tough allergenic molecule

Food allergies are recognized as an increasing health concern. Proteins commonly identified as food allergens tend to have one of about 30 different biochemical activities. This leads to the assumption that food allergens must have specific structural features which causes their allergenicity. But these structural features are not completely understood. Uncovering the structural basis of allergenicity would allow improved diagnosis and therapy of allergies and would provide insights for safer food production. The availability of recombinant food allergens can accelerate their structural analysis and benefit specific studies in allergology. Plant chitinases are an example of food allergenic proteins for which structural analysis of allergenicity has only partially been reported. The recombinant maize chitinase, rChiA, was purified from Pichia pastoris extracellular medium by differential precipitation and cation exchange chromatography. Enzyme activity was evaluated by halo‐assays and microcalorimetric procedures. rChiA modeling was performed by a two‐step procedure, using the Swiss‐Model server and Modeller software. Allergenicity of rChiA was verified by immunoblot assays with sera from allergic subjects. rChiA is active in the hydrolysis of glycol chitin and tetra‐N‐acetylchitotetraose and maintains its activity at high temperatures (70°C) and low pH (pH 3). The molecule is also reactive with IgE from sera of maize‐allergic subjects. rChiA is a valuable molecule for further studies on structure‐allergenicity relationships and as a tool for diagnosing allergies.     

Recombination in diverse maize is stable,predictable, and associated with genetic load

Among the fundamental evolutionary forces, recombination arguably has the largest impact on the practical work of plant breeders. Varying over 1,000-fold across the maize genome, the local meiotic recombination rate limits the resolving power of quantitative trait mapping and the precision of favorable allele introgression. The consequences of low recombination also theoretically extend to the species-wide scale by decreasing the power of selection relative to genetic drift, and thereby hindering the purging of deleterious mutations. In this study, we used genotyping-by-sequencing (GBS) to identify 136,000 recombination breakpoints at high resolution within US and Chinese maize nested association mapping populations. We find that the pattern of cross-overs is highly predictable on the broad scale, following the distribution of gene density and CpG methylation. Several large inversions also suppress recombination in distinct regions of several families. We also identify recombination hotspots ranging in size from 1 kb to 30 kb. We find these hotspots to be historically stable and, compared with similar regions with low recombination, to have strongly differentiated patterns of DNA methylation and GC content. We also provide evidence for the historical action of GC-biased gene conversion in recombination hotspots. Finally, using genomic evolutionary rate profiling (GERP) to identify putative deleterious polymorphisms, we find evidence for reduced genetic load in hotspot regions, a phenomenon that may have considerable practical importance for breeding programs worldwide.Although the selective pressures contributing to its origin and persistence continue to be debated, recombination is widely recognized for its roles in promoting the diversity necessary to respond to continually shifting environments, in addition to preventing the build-up of genetic load by decoupling linked deleterious and beneficial variants (1–3). In practice, increased local recombination enhances breeders’ abilities to map quantitative traits and introduce favorable alleles into breeding lines.Recombination’s importance has spurred interest in the causes and predictability of the local recombination frequency, which is usually characterized by hotspots with cross-over rates of up to several hundred-fold the genomic background (4–6). The predictability across diverse sources of germplasm is particularly salient in maize, a species with many large structural variants in which the average genetic distance between two inbred lines exceeds that between humans and chimpanzees (7). Moreover, elevated residual heterozygosity within low-recombining regions of maize recombinant inbred lines (RILs) suggests that heterosis in maize results from complementation of alternative deleterious alleles within these regions by dominant beneficial alleles segregating in repulsion (8–10). These low-recombination regions include the large [∼100 megabases (Mb)] pericentromeres harbored by all chromosomes, which collectively contain ∼20% of the gene space (9). Despite high theoretical interest for over 50 y and the practical utility of deleterious variant discovery, the genome-wide relationship between recombination rate and genetic load is poorly studied in plant genomes with the size, repeat composition, and genetic diversity typical of maize.On a molecular level, chromatin structure heavily influences the cross-over rate in plants. Not only are heterochromatic regions generally depleted of cross-overs (11), but KO of cytosine-DNA-methyl-transferase (MET1) in Arabidopsis thaliana leads to both genome-wide CpG hypomethylation and a relative increase in the proportion of cross-overs within the euchromatic chromosomal arms (12–14). Nucleotide content may also be associated with the local frequency of recombination, potentially due to the effect of GC-biased gene conversion (bGC) during resolution of heteroduplexes that form at cross-over junctions (15).In this study we use genotyping-by-sequencing (GBS) data (16) to identify the locations of 136,000 cross-over events in the US and Chinese (CN) maize nested association mapping (NAM) populations, two sets of RILs derived from crosses of inbred maize founder lines to distinct common parents. We show that despite the tremendous diversity among NAM founders within and between these two families, recombination is remarkably consistent and associated with a number of genomic features on a fine scale, including probable deleterious variation.     

An analysis of ozone damage to historical maize and soybean yields in the United States

Numerous controlled experiments find that elevated ground-level ozone concentrations ([O₃]) damage crops and reduce yield. There have been no estimates of the actual yield losses in the field in the United States from [O₃], even though such estimates would be valuable for projections of future food production and for cost–benefit analyses of reducing ground-level [O₃]. Regression analysis of historical yield, climate, and [O₃] data for the United States were used to determine the loss of production due to O₃ for maize (Zea mays) and soybean (Glycine max) from 1980 to 2011, showing that over that period production of rain-fed fields of soybean and maize were reduced by roughly 5% and 10%, respectively, costing approximately $9 billion annually. Maize, thought to be inherently resistant to O₃, was at least as sensitive as soybean to O₃ damage. Overcoming this yield loss with improved emission controls or more tolerant germplasm could substantially increase world food and feed supply at a time when a global yield jump is urgently needed.The United States accounts for over one-third of global maize production and almost one-third of soybean production. It is also the largest exporter of both commodities (1). Numerous controlled environment and field studies have shown that current ozone concentrations ([O₃]) are damaging to the yields of both crops (synthesized by refs. 2 and 3), although soybean is reportedly more sensitive than maize, based on manipulative dose–response experiments (2). This has important implications for current crop production considering that ground-level [O₃] during the Northern Hemisphere growing seasons frequently exceed 40 ppb (4), the threshold concentration for a cumulative exposure index used in Europe, as well as the concentration above which prolonged exposure leads to significant crop yield loss (5, 6). Globally, [O₃] is projected to increase over this century if current high emissions continue (7). Although crop loss from O₃ has been estimated by extrapolating from experimental data to field conditions (8), until recently it has not been possible to quantitatively define crop loss due to O₃ pollution from actual yield data across the major US growing region.Ozone causes damage by entering leaf intercellular air spaces via stomata, where it reacts with compounds in the exposed wet cell-wall surfaces, causing the production of damaging radicals and signaling that accelerates senescence (9, 10). It also causes chain reactions, creating other reactive oxygen species, which can cause further damage, and large doses of O₃ can induce programmed cell death (11). Because the route of entry is through the stomata, O₃ damage is dependent on stomatal conductance, which is itself dependent on environmental conditions such as water availability. As such, O₃ damage is strongly dependent on environmental conditions and physiological plant properties that affect stomatal conductance. This has led to the expectation that O₃ damage will be less for C₄ species such as maize, given their intrinsically lower stomatal conductance, as well as for plants under drought stress, and in response to rising [CO₂] (9, 12).Estimating the loss of crop production from ground-level O₃ is valuable for understanding the potential benefits of reducing [O₃] and for projecting future food supply (13). Even though manipulative experiments clearly indicate that elevated [O₃] reduces soybean yields, and to a lesser extent maize yields (2), deriving field-level estimates using data from experimental studies is problematic. The environmental conditions of controlled environment studies represent only a small range of the conditions experienced by crops in fields, and because of the interactions between the effects of [O₃] and microclimate, extrapolating from controlled environment experiments to open-air field conditions is uncertain (14). The few field studies that have been conducted were done at a limited number of locations and with a limited number of genotypes. Dose–response functions created from such studies do not account for the interactions between environment and O₃ damage described above, potentially making extrapolation of losses to entire growing regions unreliable. Multivariable models that include environmental variables as well as [O₃] can account for these interactions, providing better estimates of O₃ damage.As an alternative to manipulative experiments, studies have used long-term datasets to examine the effects of temperature, precipitation, and [CO₂] on crop yield (15, 16). Ground-level [O₃] has been monitored widely in the United States for the past 30 y, and coupled with long-term county yield records, there is a new opportunity to determine the effect of [O₃] on yields by quantifying the covariance between [O₃] and yield. Using historical [O₃] and yield records requires an accounting of variation in the numerous other factors that affect yield (13, 16, 17). However, this approach has the substantial advantage of allowing for estimation of effects over most of the US growing region, given simultaneous records of surface [O₃]. Furthermore, because these estimates are independent of experimental studies, they provide a separate test and quantification of the damaging effects of O₃ on crop yields.In this study, we use [O₃] data from the Environmental Protection Agency (EPA) coupled with crop yield data from the National Agriculture Statistics Service and climate data from the Climate Research Unit to estimate production loss of maize and soybean in the United States over the past 30 y by creating a statistical model that accounts for climate, [O₃] and improvements in agronomy, with the objective of estimating production losses of these two crops due to ground-level [O₃]. Results show that from 1980 to 2011 O₃ has reduced maize yields by 10% and soybean by 5%. On a relative basis, both crops are more sensitive to [O₃] in extreme temperatures and dry conditions, and maize is more sensitive to [O₃] than soybean.     

Challenges in testing genetically modified crops for potential increases in endogenous allergen expression for safety

Premarket, genetically modified (GM) plants are assessed for potential risks of food allergy. The major risk would be transfer of a gene encoding an allergen or protein nearly identical to an allergen into a different food source, which can be assessed by specific serum testing. The potential that a newly expressed protein might become an allergen is evaluated based on resistance to digestion in pepsin and abundance in food fractions. If the modified plant is a common allergenic source (e.g. soybean), regulatory guidelines suggest testing for increases in the expression of endogenous allergens. Some regulators request evaluating endogenous allergens for rarely allergenic plants (e.g. maize and rice). Since allergic individuals must avoid foods containing their allergen (e.g. peanut, soybean, maize, or rice), the relevance of the tests is unclear. Furthermore, no acceptance criteria are established and little is known about the natural variation in allergen concentrations in these crops. Our results demonstrate a 15‐fold difference in the major maize allergen, lipid transfer protein between nine varieties, and complex variation in IgE binding to various soybean varieties. We question the value of evaluating endogenous allergens in GM plants unless the intent of the modification was production of a hypoallergenic crop.     

Nutritional and Sensory Properties of High Energy/Nutrient Dense Composite Flour Porridges from Germinated Maize and Roasted Beans for Child-Weaning in Developing Countries: A Case for Uganda

The study aimed at increasing the energy and nutrient density of traditional weaning porridges from germinated maize and decorticated bean flours. Proximate analysis showed that the porridge from the composite flour had a higher protein and energy density than typical weaning porridges made from maize alone. For a breastfed infant, the blend could meet 75% of the remaining required energy, compared to 52% provided by the porridge from maize alone. Untrained sensory evaluation panelists scored the porridge from the blend as acceptable. This blend therefore has great potential as a weaning food in resource-poor and technologically under-developed countries.