Enzymatic degradation is an effective means to reduce aflatoxin contamination in maize

Background Aflatoxins are carcinogenic compounds produced by certain species of Aspergillus fungi. The consumption of crops contaminated with this toxin cause serious detrimental health effects, including death, in both livestock and humans. As a consequence, both the detection and quantification of this toxin in food/feed items is tightly regulated with crops exceeding the allowed limits eliminated from food chains. Globally, this toxin causes massive agricultural and economic losses each year. Results In this paper we investigate the feasibility of using an aflatoxin-degrading enzyme strategy to reduce/eliminate aflatoxin loads in developing maize kernels. We used an endoplasmic reticulum (ER) targeted sub-cellular compartmentalization stabilizing strategy to accumulate an aflatoxin-degrading enzyme isolated from the edible Honey mushroom Armillariella tabescens and expressed it in embryo tissue in developing maize kernels. Three transgenic maize lines that were determined to be expressing the aflatoxin-degrading enzyme both at the RNA and protein level, were challenged with the aflatoxin-producing strain Aspergillus flavus AF13 and shown to accumulate non-detectable levels of aflatoxin at 14-days post-infection and significantly reduced levels of aflatoxin at 30-days post-infection compared to nontransgenic control Aspergillus-challenged samples. Conclusions The expression of an aflatoxin-degrading enzyme in developing maize kernels was shown to be an effective means to control aflatoxin in maize in pre-harvest conditions. This aflatoxin-degradation strategy could play a significant role in the enhancement of both US and global food security and sustainability.

High Maternal Serum Estradiol in First Trimester of Multiple Pregnancy Contributes to Small for Gestational Age via DNMT1-Mediated CDKN1C Upregulation

High maternal serum estradiol (E2) levels in the first trimester of pregnancy are associated with a high incidence of low birth weight (LBW) and small for gestational age (SGA). This study aimed to investigate the effect of first-trimester high maternal serum E2 levels on fetal growth and the underlying mechanisms in multiple pregnancies. Maternal serum E2 levels of women at 8 weeks of gestation were measured. The expression levels of imprinted genes and DNMT1 were determined by RT-qPCR, and KvDMR1 methylation in embryo tissue, placenta, and newborn cord blood samples was examined by bisulfite sequencing PCR. The effect of E2 on CDKN1C expression was investigated in HTR8 cells. The incidence of SGA was significantly higher in multiple pregnancies reduced to singleton than that in primary singleton pregnancies (11.4% vs. 2.9%) (P < 0.01) and multiple pregnancies reduced to twins than primary twins (38.5% vs. 27.3%) (P < 0.01). The maternal serum E2 level at 8 weeks of gestation increased with the number of fetuses and was negatively correlated with offspring birth weight. CDKN1C and DNMT1 expression was significantly upregulated in embryo tissue, placenta, and cord blood from multiple pregnancies. Furthermore, there was a positive correlation between CDKN1C mRNA expression and KvDMR1 methylation levels. In HTR8 cells, DNMT1 mediated the estrogen-induced upregulation of CDKN1C, which might contribute to SGA. To minimize the risks of LBW and SGA, our findings suggest that abnormally high maternal serum E2 levels should be avoided during the first trimester of multiple pregnancies from assisted reproductive technology (ART).

The dorsal blastopore lip is a source of signals inducing PCP in the Xenopus neural plate

Coordinated polarization of cells in the tissue plane, known as planar cell polarity (PCP), is associated with a signaling pathway critical for the control of morphogenetic processes. Although the segregation of PCP components to opposite cell borders is believed to play a critical role in this pathway, whether PCP derives from egg polarity or preexistent long-range gradient, or forms in response to a localized cue remains a challenging question. Here we investigate the Xenopus neural plate, a tissue that has been previously shown to exhibit PCP. By imaging Vangl2 and Prickle3, we show that PCP is progressively acquired in the neural plate and requires a signal from the posterior region of the embryo. Tissue transplantations indicated that PCP is triggered in the neural plate by a planar cue from the dorsal blastopore lip. The PCP cue did not depend on the orientation of the graft and was distinct from neural inducers. These observations suggest that neuroectodermal PCP is not instructed by a preexisting molecular gradient, but induced by a signal from the dorsal blastopore lip.

The dorsal blastopore lip is a source of signals inducing PCP in the Xenopus neural plate

Coordinated polarization of cells in the tissue plane, known as planar cell polarity (PCP), is associated with a signaling pathway critical for the control of morphogenetic processes. Although the segregation of PCP components to opposite cell borders is believed to play a critical role in this pathway, whether PCP derives from egg polarity or preexistent long-range gradient, or forms in response to a localized cue remains a challenging question. Here we investigate the Xenopus neural plate, a tissue that has been previously shown to exhibit PCP. By imaging Vangl2 and Prickle3, we show that PCP is progressively acquired in the neural plate and requires a signal from the posterior region of the embryo. Tissue transplantations indicated that PCP is triggered in the neural plate by a planar cue from the dorsal blastopore lip. The PCP cue did not depend on the orientation of the graft and was distinct from neural inducers. These observations suggest that neuroectodermal PCP is not instructed by a preexisting molecular gradient, but induced by a signal from the dorsal blastopore lip.

Variation in zinc concentration of sweetcorn kernels reflects source–sink dynamics influenced by kernel number

Grain yield and mineral nutrient concentration in cereal crops are usually inversely correlated, undermining biofortification efforts. Here, sink size, expressed as kernel number per cob, was manipulated by controlling the time when the silks of sweetcorn (Zea mays) cv. Hybrix 5 and var. HiZeax 103146 were exposed to pollen. Twelve other varieties were manually pollinated to achieve the maximum potential kernel number per cob, and kernel Zn concentration was correlated with kernel number and kernel mass. As kernel number increased, kernel Zn concentration decreased, with the decrease occurring to similar extents in the embryo tissue and the rest of the kernel. However, total kernel Zn accumulated per cob increased with increasing kernel number, as the small decreases in individual kernel Zn concentration were more than offset by increases in kernel number. When both kernel number and mass were considered, 90% of the variation in kernel Zn concentration was accounted for. Differential distribution of assimilates and Zn to sweetcorn cobs led to significant decreases in kernel Zn concentration with increasing kernel number. This suggests there will be challenges to achieving high kernel Zn concentrations in modern high-yielding sweetcorn varieties unless genotypes with higher Zn translocation rates into kernels can be identified.

Reserve metabolism of stored and germinated Araucaria angustifolia seeds

Germination metabolism of recalcitrant seeds of Araucaria angustifolia is activated in storage, which complicates the seeds conservation and utilization. This study aimed to identify the changes in the reserve metabolites of A. angustifolia seeds throughout storage in order to understand the processes of hydrolysis caused by germination metabolism. Mature seeds were harvested in southern Brazil and stored in an ambient environment and cold chamber conditions. Biochemical analyses were performed for embryos and megagametophytes from seeds stored for 0, 15, 30, 45, and 90 days. Due to seeds being in advanced germination in storage, they were evaluated at 90 days in different early developmental categories: I – seeds with mature embryos, II – seeds with embryos showing apparent elongation along the embryonic axis, and III – seeds with root protrusion. Higher contents of carbohydrate, protein, and amino acids were observed in embryos compared to megagametophytes, and these metabolites were decreased after onset of germination, especially in the embryo tissue. Mobilization of metabolites in megagametophytes would probably increase in later stages of germination. It is suggested that such alterations are not due to deterioration of reserve components, but instead are based on seed metabolism, which remains active after harvest with hydrolysis of metabolites providing energy for germination.

Comparison of different cytogenetic methods and tissue suitability for the study of chromosomes in Cimex lectularius (Heteroptera, Cimicidae)

In the article we summarize the most common recent cytogenetic methods used in analysis of karyotypes in Heteroptera. We seek to show the pros and cons of the spreading method compared with the traditional squashing method. We discuss the suitability of gonad, midgut and embryo tissue inCimexlectulariusLinnaeus, 1758 chromosome research and production of figures of whole mitosis and meiosis, using the spreading method.The hotplate spreading technique has many advantages in comparison with the squashing technique. Chromosomal slides prepared from the testes tissue gave the best results, tissues of eggs and midgut epithelium are not suitable. Metaphase II is the only division phase in which sex chromosomes can be clearly distinguished. Chromosome number determination is easy during metaphase I and metaphase II. Spreading of gonad tissue is a suitable method for the cytogenetic analysis of holokinetic chromosomes ofCimexlectularius.

Postdispersal Infection and Disease Development of Pyrenophora semeniperda in Bromus tectorum Seeds

The Ascomycete fungus, Pyrenophora semeniperda, attacks a broad range of cool-season grasses. While leaf and predispersal infection of seeds (i.e., florets containing caryopses) have been previously characterized, little is known about the pathogenesis of mature seeds following dispersal. In this study, we examined infection and disease development of P. semeniperda on dormant seeds of Bromus tectorum. Inoculated seeds were hydrated at 20°C for up to 28 days. Disease development was characterized using scanning electron and light microscopy. P. semeniperda conidia germinated on the seed surface within 5 to 8 h. Hyphae grew on the seed surface and produced extracellular mucilage that eventually covered the seed. Appressoria formed on the ends of hyphae and penetrated through the lemma and palea, stomatal openings, and broken trichomes. The fungus then catabolized the endosperm, resulting in a visible cavity by 8 days. Pathogenesis of the embryo was associated with progressive loss of cell integrity and proliferation of mycelium. Beginning at approximately day 11, one to several stromata (approximately 150 μm in diameter and up to 4 mm in length) emerged through the lemma and palea. Degradation of embryo tissue was completed near 14 days. Conidiophores produced conidia between 21 and 28 days and often exhibited “Y-shaped” branching. This characterization of disease development corrects previous reports which concluded that P. semeniperda is only a weak seed pathogen with infection limited to the outermost seed tissues. In addition, the time required for disease development explains why infected dormant or slow-germinating seeds are most likely to experience mortality.

Evaluating different passive optical clearing protocols for two-photon deep tissue imaging in adult intact visceral and neuronal organs

Imaging cellular activities in an entire intact whole organ with light is a grand challenge in optical microscopy. To date, most passive clearing techniques were shown to transform brain, neuronal and embryo tissue into near transparent state for deep tissue imaging. Here, we expand these passive clearing protocol from neuronal tissue (brain and spinal cord) to other visceral organs such as liver and colon and further evaluate their ?depth-clearing performance? based on image contrast of endogenous fluorescence structures. We found that the SeeDB achieve highest depth in brain, 3DISCO is adept at clearing liver and spinal cord and ScaleViewA2 in colon. Overall, 3DISCO clears more rapidly than other agents at a higher cost, while ScaleViewA2 is the most economical but clears at a slower rate. This study, for the first time, provide a direct evaluation of imaging depth, cost and time amongst passive tissue clearing protocols for different intact organs.