Citrus greening, or “yellow dragon’s disease”, originally originated in Asia, but has affected trees in Africa and the Western Hemisphere for more than a decade. This infectious disease of citrus trees is transmitted from plant to plant through insects (Diaphorina citri). The causative agents are bacteria of the genus Candidatus Liberibacter asiaticus (CLas). Of all the citrus diseases, yellow dragon disease stands out as causing the most damage to plantations. Common symptoms include early yellowing and leaf fall, branch death, off-season flowering and ripening of small, irregularly shaped, thick green skins and sour fruit flavors.

Insecticides are now used to control disease vectors, and antibiotics are used to control the growth of pathogenic bacteria. However, none of the methods has been shown to be effective enough in controlling the disease. Experts hope for the innate immunity of plants: usually when faced with an infection, the plant’s defense system produces antimicrobial proteins. It is known that all cultivated citrus fruits are prone to greening, but there are hybrids that are resistant to CLas. Probably, disease-resistant plants just secrete antimicrobial peptides that fight pathogenic bacteria.

A team of researchers from the University of California, led by Hailing Jin, compared the template RNAs of resistant and green trees and identified a list of genes that could be responsible for protecting plants from CLas. Among them, the gene encoding a small protein of 67 amino acid residues attracted the attention of scientists. The predicted structure of the protein was similar to the heat-resistant antimicrobial peptide found in plants of the genus Arabidopsis. Similar genes have been found in related resistant citrus fruits, such as the Australian Finger Lime (Microcitrus australasica), Poncirus trifoliata, or Murraya paniculata. In cultivated oranges (Citrus sinensis) and clementines (Citrus clementine), which are poorly tolerated, such genes were longer and less actively expressed.

The researchers also tested for the presence of putative antimicrobial peptides in the phloem conducting plant tissue, where pathogens are usually concentrated. Proteins were found in the phloem of the finger lime and poncirus, they were not seen in the phloem of oranges. Together, these results suggest that antimicrobial peptides are most likely responsible for the resistance of citrus to CLas.

To test the effectiveness of antimicrobial peptides, the researchers used a previously created model that mimics infection in nature: insects with a positive test for the presence of pathogenic bacteria fed on the plant, and with the saliva of insects, the bacteria entered the plant. The model used Bactericera cockerelli and young tobacco-related plants Nicotiana benthamiana. The leafhopper does not usually feed on tobacco, but sometimes bites its young shoots. Tobacco, in turn, is usually not subject to greening, but its young sprouts turn slightly yellow in case of infection with Candidatus Liberibacter bacteria. It was chosen because citrus fruits grow slowly and show symptoms for a long time, and tobacco – much faster. To quickly assess the extent of infection and the effect of antimicrobial peptides on bacteria in this model, Bactericera cockerelli and Nicotiana benthamiana are used instead of Diaphorina citri and citrus. The plants were then treated with antimicrobial peptides derived from different resistant trees. Antimicrobial peptides from finger lime were the best at suppressing the growth of bacteria in plants. It was with this protein that further experiments were conducted.

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35 percent of the world’s crop production depends on pollinating insects, and their numbers have continued to decline since the last century. Despite this, the most popular insecticides are neonicotinoids, which act nonspecifically and cause damage to all insects at once: both harmful and beneficial. Some of them have even been banned by the European Union, but even there traces of pesticides are still found in bumblebee populations. Neonicotinoids also dissolve well in water, which traps them in ecosystems.

Neonicotinoids have a negative effect on insects through nicotinic receptors in neurons: insecticides bind to them and cause excessive excitation in the brain. Insects have such receptors in the fungal body, the structure of the brain that is responsible for memory. Nicotine receptors are also involved in transmitting visual signals about illumination and setting the biological clock. The effect of neonicotinoids on memory and sleep in insects has not been sufficiently studied.

Researchers at the University of Bristol, led by Kiah Tasman, studied the effects of neonicotinoids on a model insect, the fruit fly Drosophila Melanogaster. Biologists first confirmed the overall negative effects of insecticides on Drosophila: as with bumblebees, flies had reduced life expectancy, motility and fertility after exposure to substances in concentrations used in agriculture.

Biologists also evaluated the effects of insecticides on Drosophila memory and tested how insects can remember odors. Scientists fed them insecticides, then evaluated the memory: combined different odors with electric shocks to create an unpleasant association in flies, and an hour later asked the insects to remember the unpleasant odor. To do this, they were placed in a long sleeve of T-shaped design, where the remaining two sleeves were odors: unpleasant and control. The more Drosophila chose the control odor due to unpleasant associations with the current, the better the memory performance of the group.

Three of the four neonicotinoids, imidacloprid, clothianidin, and thiamethoxam, impaired memory in Drosophila (p <0.05). To assess the role of the fungal body’s nicotinic receptors, which is responsible for memory in insects, biologists partially “turned them off” and repeated the experiment without neonicotinoids. After that, fruit flies also had a reduced ability to remember odors, which indicates the need for these receptors to remember.

The researchers also studied circadian rhythms in Drosophila after insecticide feeding. They used special activity monitors – cells that recorded the mobility of flies, which judged sleep and wakefulness. The same three insecticides significantly disrupted the circadian rhythms of Drosophila (p <0.001). Also, all neonicotinoids caused restless sleep in flies: the number of sleep episodes increased, but each of them became much shorter.

Biologists have also confirmed the role of nicotinic receptors in this process, but already in the neural networks of Drosophila biological clocks: their partial shutdown caused similar effects. Neonicotinoids have also caused disturbances in flies in the cyclic processes of day and night: normally, the processes of their neurons in the biological clock branch more and form connections during the day than at night. However, after exposure to imidacloprid and clothianidin, no such differences between day and night were observed.

Thus, British researchers have been able to show that the most common insecticides have a strong effect on the brain of insects and prevent them from functioning, disrupting the work of nicotine receptors in the structures of memory and the biological clock. Most likely, this also applies to pollinating insects, which are important for agriculture, so the data in this article are a reason to reconsider the use of neonicotinoids and continue the search for more specific insecticides.

In order for Drosophila to sleep well, you can not only eliminate insecticides from their diet, but also lull them. We recently wrote that rhythmic swaying helps fruit flies sleep longer because of getting used to a certain stimulus.

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Skeletal muscles make up about 45 percent of a person’s body weight, and their ability to contract is necessary to maintain viability. Healthy muscles can regenerate after minor injuries with the help of muscle stem cells. This process is triggered by a local and systemic inflammatory response, in particular, the interferon-gamma cytokine (IFN-γ) regulates the process of muscle tissue formation. And if the inflammation caused by the injury stimulates the muscles to regenerate, then unregulated inflammatory processes, which are characteristic of some diseases, lead to loss of muscle mass and muscle weakness. Such diseases include, for example, chronic obstructive pulmonary disease, rheumatoid arthritis and dermatomyositis. In addition, elevated levels of IFN-γ in the blood are usually seen after the flu or cytokine storm due to severe covid.

The link between chronic inflammation and muscular dystrophy has been confirmed by rodent experiments and clinical studies. Appropriate in vitro studies have not been performed due to the lack of suitable models: conventional muscle cell culture does not reproduce many properties of muscle tissue. Previous work has suggested that IFN-γ affects muscles by activating the JAK / STAT signaling pathway.

Earlier, a team of researchers from Duke University (USA) led by Nenad Bursac developed a 3D model of human skeletal muscle (“muscle bundles”). Scientists then showed that muscle bundles respond to electrical stimulation that mimics exercise, with corresponding changes in metabolism and an increase in size and strength. In a new study, the same group of scientists described the mechanism of the direct effect of IFN-γ on the structure and function of skeletal muscle, and also showed the positive effect of exercise.

The researchers studied the effect of IFN-γ on muscle bundles cultured from cells from three independent donors. The beams were treated with interferon at a dose of 20 nanograms per milliliter for a week, and then checked for changes in their structure, biochemical and functional properties, and in the release of cytokine signaling molecules. In this case, some cells during the experiment received not only doses of interferon, but were exposed to electrical effects, which mimicked exercise. Another part only “went in for sports”.

The muscle bundles that received IFN-γ were weakened compared to the control group. For example, interferon reduced the amplitude of tetanus, a long-lasting muscle contraction, by 68 percent. Electrical stimulation improved cell performance, bringing it closer to that of the control group, which was not exposed to interferon.

The effects of interferon alone did not lead to muscle loss. However, those cells that only “exercised” gained more weight than those that received electrical stimulation at the same time as interferon doses. Interferon reduced the diameter of the muscle tubules (8.8 micrometers against 11.3 micrometers in cells from the control group), and electrical stimulation reversed this effect. A similar trend was observed when measuring cell length. “Exercise” also had a beneficial effect on the expression of contractile proteins in cells.

Exposure to interferon also affected the composition of signaling molecules secreted by cells: the content of some pro-inflammatory cytokines increased in the medium. And this effect was reversible by electrical stimulation of cells.

Electrical stimulation partially (by 50 percent) attenuated the activation of the JAK / STAT signaling pathway in muscle bundles. This proves that in addition to the direct benefits of exercise, there is a certain molecular mechanism that provides the anti-inflammatory effect of “exercise”, which prevents muscle weakness. In addition, existing Janus kinase (JAK) inhibitors, tofacitinib and baricitinib at clinical doses, also prevented structural and functional loss in muscle cells.

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In winter, instead of warm yellow lights, you can often see an ominous purple glow in the windows of apartment buildings. These are glowing phytolamps, with the help of which amateur florists hope to cheer up their houseplants and seedlings. We tell why they use such an unusual light, whether it really helps plants and how the astronauts participated in this story.

A rare plant lover – whether he has his own farm or just a couple of tubs on the windowsill – does without fertilizers. However, plants feed not only through the roots, but also through the leaves, which absorb carbon dioxide and light. Does this mean that they can be “fed” not only with fertilizers but also with light? And can this force them to yield even more?

Which light is tastier?

Kliment Timiryazev and Teodor Engelman found the answer to this question independently of each other in the second half of the 19th century. They decomposed sunlight into a spectrum, illuminated it with different parts of the plant, and measured how actively they photosynthesized (that is, absorbed carbon dioxide, released oxygen, and produced sugar). They used slightly different techniques, but obtained similar results. It turned out that not every part of the spectrum causes the sheet to absorb carbon dioxide and emit oxygen with equal efficiency. It worked best in red and blue light, and worst in green. The fact is that the pigments that capture light for photosynthesis – chlorophylls and carotenoids – absorb red and blue light well, and almost do not react to green.

Later, the same Timiryazev found out that red has another valuable property. The energy trapped in the red rays is used almost entirely by the leaf to form biomass – while in the blue light there is too much energy, so half is “lost” in the form of heat. So, you can save: if you illuminate greenhouses with one red light, electricity will be used more efficiently and will not be lost, and plants will become more productive – will be able to accumulate more nutrients than if they grew under normal sunlight.

There is only one thing: plants need light not only for photosynthesis. And also, for example, to determine in which direction to grow, when to bloom and bear fruit. In addition, the light triggers the opening of the stomata (through which the leaf exchanges gases with air) and regulates the circadian rhythms of leaf movement and flower opening. To do this, plant cells have special molecules – photoreceptors, which change the expression of genes and metabolism in the cell in response to light rays. The main photoreceptors of plants, as well as photosynthesis pigments, work with red and blue light, but can also catch green, ultraviolet and far red.

It turns out that the life of a plant depends on the sum of light signals of different colors, but what effect each of them produces in the absence of others, plant physiologists in Timiryazev’s time did not know – and do not quite understand until now. Therefore, the replacement of natural light with pure red rays can not lead to an increase in yield, but to the exact opposite result – theoretically in such conditions, plants should wither or at least give less fruit than usual.

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Polyunsaturated alkenes are used in the production of pharmaceuticals and the synthesis of polymers, and now these substances are obtained from fossil fuels. Instead, scientists are looking for a renewable alternative.

One of the available options is to apply metabolic engineering techniques. Researchers have already learned to force bacteria to produce certain substances necessary for humans (including those that are not characteristic of these bacteria), or, conversely, to break down unnecessary ones (for example, polyethylene). To do this, scientists can overexpress the necessary genes in bacteria, block competing metabolic pathways, or express genes specific to other microorganisms, as well as apply enzyme engineering techniques. Work is underway to expand the list of substances that can be obtained using metabolic engineering methods.

There are decarboxylase enzymes capable of converting unsaturated carboxylic acids into the corresponding alkenes. It has also been shown that the bacterium Pantoea agglomerans in the natural process of biosynthesis of andrimidide, important for its metabolism, produces as an intermediate a derivative of 2,4,6-octatrienic acid. Combining these facts, scientists from the University of Manchester, David Leys, came up with a way to teach E. coli to synthesize hepta-1,3,5-triene, one of the representatives of polyunsaturated alkenes.

To begin with, biologists removed seven genes (which accounted for a third of the cluster) from the cluster of P. agglomerans genes required for andrimid synthesis, and introduced the remaining construct into Escherichia coli cells. Thus, 2,4,6-octatrienic acid with a concentration of 14.7 ± 2.0 milligrams per liter was developed. Interestingly, the authors tried to increase the yield of the product by transforming the genetic construct, but as a result got the opposite result – the complete absence of matter. The researchers suggested that there are some elements, not yet known to them, that control acid synthesis, and this will be known in future experiments.

Next, the scientists combined the resulting working construct with the decarboxylase gene from fungal cells. The production of hepta-1,3,5-triene was confirmed by gas chromatography coupled by mass spectrometry. The researchers estimated that the product concentration was 3.4 ± 0.3 milligrams per liter. The authors believe that they have shown an important example of the production of unsaturated hydrocarbons in vivo.

Not only biologists and chemists, but also physicists like to experiment with E. coli. For example, Spanish scientists tore a E. coli cell.

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Adeno-associated virus is often used as a vector (carrier) for gene therapy: to do this, the virus is deprived of part of its own genetic information and replaced with the necessary. It was the adeno-associated virus that became the basis for the first medically approved gene therapy, and several other similar drugs are undergoing clinical trials.

In creating vectors for therapy, bioengineers seek to change the natural capsid, the outer protein shell of the virus, inside which the genetic material is hidden, and give it the desired properties. For example, capsid proteins determine whether the therapy is specific to any tissue in the body. To create a device that targets a specific tissue or organ, it is necessary to obtain a viral particle, the capsid of which will have an increased ability to infect this tissue. In addition, the immune system of many people may already be familiar with the natural adeno-associated virus and will actively suppress the particles actually intended for treatment. To prevent this from happening, it is necessary to make the capsid as unrecognizable as possible for immunity.

There are a number of methods in the arsenal of molecular biologists for changing the capsid, such as randomly shuffling parts of the genome encoding capsid proteins, or introducing random mutations. However, not all of the resulting genetic variants are viable (that is, they can form viral particles), and many of the successful capsids are still too similar to natural variants.

Scientists at Harvard University, led by Eric Kelsic, decided to use machine learning to create a model that would generate the design of viral particles and evaluate their functionality. To work, the researchers chose a 28-amino acid site that includes antibody-recognized sites.

Scientists first created a dataset of viral genetic information to train the model. To do this, the scientists first introduced either one amino acid substitution at each of the 28 selected positions in the capsid protein, or randomly from two to ten mutations in this region. In the two groups of viral particles obtained, the viability was 58 and 10 percent, respectively. The authors then randomly combined mutations from these two groups to obtain a third. Combining sequences from the three groups in different ways, the researchers obtained three data sets of different sizes to teach the model. For each of the three sets, the researchers applied three types of model architecture: logistic regression, convolutional neural network, and recurrent neural network.

The researchers obtained two sets of sequences: those that were evaluated by the algorithms and those that were compiled by them. Each of the sequences carried from 5 to 29 mutations. Scientists synthesized 201426 of them and evaluated their viability experimentally.

Based on the baseline model, the researchers expected that 62.5 percent of the machine-assisted capsids would be functional and that no capsid with more than 21 mutations at a given site would be viable. In fact, the algorithms did a good job of designing new proteins: 58.1 percent of the sequences they made (110,689 variants) formed functional capsids. Most importantly, 57,348 viable variants turned out to have 12 to 29 mutations in a given region, which strongly distinguished them from natural capsids (and exceeded the expectations of the authors). The second task, the assessment of viability, also performed well on neural networks: the prediction accuracy reached almost one hundred percent for variants carrying up to six mutations in a given area compared to a natural virus.

The authors note that the variants of the adeno-associated virus found during the study are promising candidates for vectors. It is possible that the new particles will have the functions required by different researchers: for example, increased tropism to the cells of certain tissues, or they will be easily produced on an industrial scale.

The adeno-associated virus vector was the first FDA-approved gene therapy. Clinical trials of hemophilia B gene therapy have also been successfully completed; such therapy for hemophilia A (and also with adeno-associated virus as a vector) has been called effective and safe in the long run.

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