Articles of the Month 2021
Archive of previous entries
Some of the most severe insect pests are invasive species such as Drosophila suzukii. Their invasive success is achieved in part due to their extremely robust immune system, which makes them difficult to control. In December's article of the month, Carrau et al. investigate the innate immunity of D. suzukii and reveal some of the underlying mechanisms. In the human immune system, one of the first lines of defense against invading bacteria is the activation of neutrophils, which catch bacteria in so-called neutrophil extracellular traps (NETs) formed from the cells' own DNA as they die. Carrau et al. found that the equivalent immune cells in D. suzukii (plasmatocytes) also produce extracellular traps, in addition to deploying other strategies such as engulfing the invading bacteria (phagocytosis) and trapping them on cellular extensions (filopodia). The more we learn about the defense mechanisms of insect pests, the easier it becomes to develop strategies that overcome or circumvent those mechanisms as a means of pest control.
Article details: Carrau T et al. (2021) The cellular innate immune response of the invasive pest insect Drosophila suzukii against Pseudomonas entomophila involves the release of extracellular traps. Cells 10 (12) 3320.
Image shows a neutrophil (yellow) that has ejected a NET (green) to capture bacteria (purple), with the collateral effect of also trapping a red blood cell (orange).
Image credit: CHDENK (CC BY-SA 4.0)
Insect pests cause immense damage to crops, but traditional control methods based on chemical pesticides are becoming less effective because insect populations are evolving resistance. One way to counter this is the release of volatile compounds (odorants) that direct insect behavior, including their ability to identify food, mates, and predators, but the underlying molecular mechanisms are often unclear. In November's article of the month, Chen et al. show how the volatile compound methyl eugenol is detected by the oriental fruit fly (Bactrocera dorsalis). They provide direct physical evidence that methyl eugenol binds to the receptor BdorOBP56f-2, and then confirm its biological role by knocking out the corresponding gene and showing that flies no longer respond to this chemical. Uncovering the molecular basis of odorant perception in pest insects will facilitate the development of new control strategies to protect crops.
Article details: Chen X et al. (2021) CRISPR/Cas9 mutagenesis abolishes odorant-binding protein BdorOBP56f-2 and impairs the perception of methyl eugenol in Bactrocera dorsalis (Hendel). Insect Biochem Mol Biol 139, 103656.
Image shows a female oriental fruit fly (Bactrocera dorsalis) laying eggs under the skin of a papaya fruit.
Image credit: Scott Bauer/USDA (public domain).
Ancient DNA can provide fascinating insights into the lives of historical figures to fill gaps in written archives or support findings based on other contemporaneous sources. As DNA sequencing technology becomes more powerful, so it becomes possible to find information even when the source material is hundreds or even thousands of years old. In October's article of the month, Iadarola et al. apply a technique known as exome sequencing to home in on the coding regions of DNA extracted from the mummified remains of Cangrande della Scala. This Italian nobleman (1291–1321) was the ruler of Verona and surrounding cities until his death, and he was interred in a marble tomb that helped to preserve his body. The reconstructed DNA sequence suggests that Cangrande della Scala represents the earliest known case of the lysosomal storage disorder now known as Pompe disease, which fits well with historical accounts of his poor health. Even small amounts of preserved tissue are sufficient for this approach, which could therefore provide new information about genetic heritage to support historical research.
Article details: Iadarola B et al. (2021) Whole-exome sequencing of the mummified remains of Cangrande della Scala (1291–1329 CE) indicates the first known case of late-onset Pompe disease. Sci Rep 11 (1) 21070.
Image shows an equestrian Statue of Cangrande della Scala at the Museo di Castelvecchio, Verona, Italy.
Image credit: this image in the public domain
Chicory is used as a salad leaf and also as an industrial source of the food additive inulin. However, the waste biomass left after inulin extraction is full of bioactive molecules that can be extracted to gain additional value. In September's article of the month, Häkkinen et al. show that chicory extracts prepared using a variety of solvents and techniques possess a remarkable range of biological activities, including the ability to suppress the growth of antibiotic-resistant bacteria and to prevent biofilm formation by the yeast Candida albicans. Plants such as chicory could therefore be used in the future as a source of natural antimicrobial compounds to address the shortage of new antibiotics in the development pipeline. Furthermore, the use of waste fractions from an existing industrial process provides a way to valorize plant material that is usually discarded or incinerated.
Article details: Häkkinen ST et al. (2021) Chicory extracts and sesquiterpene lactones show potent activity against bacterial and fungal pathogens. Pharmaceuticals 14 (9) 941.
Image shows a chicory flower.
Image credit: Jim/Code Poet (CC BY-NC-SA 2.0).
The production of recombinant proteins in plants rather than microbes or mammalian cells can be be advantageous in terms of speed, safety and scalability, but downstream processing and purification can be more challenging because the product is mixed with a large number of host cell proteins. In August's article of the month, Bernau et al. show how the mathematical modeling of chromatography can predict the most suitable conditions for protein purification, reducing the costs of process optimization. They identified the main sources of variation resulting from the selection of different chromatography settings, but also found that cultivation conditions such as the greenhouse temperature can have a profound impact on the behavior of host cell proteins and the corresponding chromatography binding parameters. The application of such models can help to improve the purification process for pharmaceutical proteins such as therapeutic antibodies.
Article details: Bernau CR et al. (2021) Precision analysis for the determination of steric mass action parameters using eight tobacco host cell proteins. J Chromatogr A 1652, 462379.
Image shows a space-filling model of the most abundant plant host cell protein, the enzyme RuBisCO.
Image credit: wwPDB, created with NGL Viewer.
The common clothes moth (Tineola bisselliella) is one of the few insect species that can digest keratin, the major protein component of wool and some other natural fabrics (as well as natural structures such as hair, nails and feathers). Although the adults do not feed, the larvae are notorious pests that destroy clothing and other textiles. In July's article of the month, Schwabe et al. provide insight into the mechanism of keratin digestion by comparing transcriptome datasets from larvae reared exclusively on keratin-rich diet of feathers and those raised on a keratin-free diet. The feather diet induced the expression of more than 30 enzymes, including collagenases and other proteases as well as enzymes that help to reduce disulfide bonds. The identification of specific enzymes that allow larvae to feed on keratin could facilitate the development of targeted control strategies based on enzyme inhibition.
Article details: Schwabe M et al. (2021) Next-generation sequencing analysis of the Tineola bisselliella larval gut transcriptome reveals candidate enzymes for keratin digestion. Genes 12 (8) 1113.
Image shows a clothes moth larva.
Image credit: Lamiot (CC BY-SA 3.0)
Biopharmaceutical proteins such as antibodies are typically produced in mammalian cells, including the human cell line HEK-293T. The yield of such proteins can be improved by cell line engineering, which aims to balance cell growth, viability and productivity. In June's article of the month, Kronenberg et al. show that a plant regulatory protein known as NtFT4, which controls flowering in response to day length in tobacco, can improve the proliferation of several human cell lines without compromising viability or productivity. The transfection of HEK-293T cells usually reduces the density of viable cells, but the expression of NtFT4 overcomes this hurdle and allows the dense cultivation of transfected cells and thereby increases the yield of a recombinant antibody by more than 30%. This engineering strategy could be combined with other forms of process optimization to boost the yield of recombinant proteins even further.
Article details: Kronenberg J et al. (2021) The tobacco phosphatidylethanolamine-binding protein NtFT4 simultaneously improves vitality, growth and protein yield in human cells. Biotechnol Bioeng 118 (10) 3770–3786.
Image shows fluorescence microscopy of HEK-293 cells loaded with the dye Flou-4.
Image credit: Borys Olifirov (CC BY 4.0)
The modification of staple cereals to increase nutrient levels in the seeds is a common approach to develop new varieties that prevent diseases of malnutrition. However, it is often unclear how such interventions affect the metabolism of the vegetative tissues of the same plants, particularly the leaves and roots. In May’s article of the month, Girón-Calva et al. carried out a comprehensive metabolic comparison of normal maize plants and a variety engineered to accumulate carotenoids in the seeds, focusing on the metabolic profiles of the leaves and roots. Not only did they find differences in vegetative metabolism between the two plant lines, but also different responses to high or low levels of nitrogen in the fertilizer. These different vegetative responses arose even before seed development and thus cannot be a direct response to metabolic engineering in the seed, suggesting that the differences are somehow already primed at the embryonic stage. This model of transgenerational metabolic priming could help to predict the outcome of metabolic engineering.
Article details: Girón-Calva PS et al. (2021) Nitrogen inputs influence vegetative metabolism in maize engineered with a seed-specific carotenoid pathway. Plant Cell Rep 40 (5) 899–911.
Image shows a collection of maize cobs.
Image credit: Parmveer Singh (CC BY-SA 3.0).
Apples and pears are consumed all over the world as part of a healthy diet. They provide a rich source of polyphenols, which are complex molecules that demonstrate a range of useful activities in vitro, including antioxidant activity. However, the benefits of dietary polyphenols are difficult to confirm directly because of the varying amounts present in different fruit cultivars as well as differences in absorption and metabolism. In April’s article of the month Commisso et al. investigate the metabolic complexity of six apple and five pear cultivars, and measure their antioxidant capacity in relation to the abundance of different polyphenol compounds. They determined the relationship between metabolic diversity and the genotype of the cultivars and the growing season, and identified cultivars with high levels of polyphenols and low levels of sugars. The metabolic profiling of different fruit cultivars will help consumers to choose fruit products with known health benefits.
Article details: Commisso M et al. (2021) Metabolomic profiling and antioxidant activity of fruits representing diverse apple and pear cultivars. Biology 10 (5) 380.
Image shows a selection of apples and pears.
Image credit: Dimitar Nikolov (CC BY 2.0)
Honeybees are in decline due to a combination of factors including habitat loss, the spread of pathogens and parasites, and the widespread use of pesticides. Honeybees are killed by high doses of pesticides and overwhelming pathogen numbers, but even lower exposure has the potential to induce stress responses that reduce colony fitness. In our article of the month for March, Bartling et al. investigate this phenomenon by testing the effects of a bacterial pathogen and four pesticides on honeybee stress responses and innate immunity when administered at low oral doses. All five stressors affected the mean lifespan of the insects and induced the production of antimicrobial and detoxifying defence factors, but the pesticides triggered a specific effect based on nitric oxide signalling. It may be possible to use these responses as markers to assess the fitness of honeybee colonies.
Article details: Bartling MT et al. (2021) Exposure to low doses of pesticides induces an immune response and the production of nitric oxide in honeybees. Sci Rep 11 (1) 6819.
Image shows the western honeybee Apis mellifera.
Image credit: Reinhard Müller (CC BY-SA 4.0)
High-content screening is a common strategy used to identify new drugs. Large libraries of diverse chemical compounds are tested systematically to determine their effect on a given disease or pathogen, allowing the most promising candidates to be selected for more detailed analysis. The development of drugs for the treatment of COVID-19 can be accelerated by screening compounds that have been tested unsuccessfully against other diseases but may already have passed clinical safety evaluation. In February’s article of the month, Ellinger et al. describe the screening of 5632 compounds (including 3488 previously tested in clinical trials for other diseases) for the ability to inhibit SARS-CoV-2. They identified 258 promising hits that were tested in dose-response trials, ultimately leading to 67 active molecules. This 10-fold reduction in the library size will allow further research to focus on the most promising antiviral molecules.
Article details: Ellinger B et al. (2021) A SARS-CoV-2 cytopathicity dataset generated by high-content screening of a large drug repurposing collection. Sci Data 8 (1) 70.
Image shows the structure of SARS-CoV-2.
Image credit: CDC/Alissa Eckert/Dan Higgins.
Coated films are widely used to protect food, electronic devices and other goods from air and moisture, but the performance of such films is influenced by numerous parameters, including temperature, humidity and exposure to light. In January's article of the month, Kiese et al. determine how temperature influences the transport of water through a plastic film (polyethylene terephthalate) coated with inorganic-organic hybrid polymers and silicon dioxide in different multilayer configurations. They developed equations to predict the behavior of the individual layers and composite films before verifying the predictions experimentally. The temperature dependence of steady-state permeation was found to depend mainly on the silicon dioxide layer, whereas the hybrid polymer layer determined the lag time for vapor transmission. The results can be used to predict the performance of barrier films in different environments, allowing the most appropriate coated films to be selected for a given purpose.
Article details: Kiese S et al. (2021) The influence of temperature on the intrinsic transport properties of water in inorganic and polymeric coatings. Thin Solid Films 717, 138476.