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Plant Signaling & Behavior Dec 2023Photosynthetic organisms biosynthesize various carotenoids, a group of light-absorbing isoprenoid pigments that have key functions in photosynthesis, photoprotection,... (Review)
Review
Photosynthetic organisms biosynthesize various carotenoids, a group of light-absorbing isoprenoid pigments that have key functions in photosynthesis, photoprotection, and phototaxis. Microalgae, in particular, contain diverse carotenoids and carotenoid biosynthetic pathways as a consequence of the various endosymbiotic events in their evolutionary history. Carotenoids such as astaxanthin, diadinoxanthin, and fucoxanthin are unique to algae. In microalgae, carotenoids are concentrated in the eyespot, a pigmented organelle that is important for phototaxis. A wide range of microalgae, including chlorophytes, euglenophytes, ochrophytes, and haptophytes, have an eyespot. In the chlorophyte , carotenoid layers in the eyespot reflect light to amplify the photosignal and shield photoreceptors from light, thereby enabling precise phototaxis. Our recent research revealed that, in contrast to the β-carotene-rich eyespot of , the euglenophyte relies on zeaxanthin for stable eyespot formation and phototaxis. In this review, we highlight recent advancements in the study of eyespot carotenoids and phototaxis in these microalgae, placing special emphasis on the diversity of carotenoid-dependent visual systems among microalgae.
Topics: Carotenoids; Microalgae; Phototaxis; Terpenes; beta Carotene
PubMed: 37724547
DOI: 10.1080/15592324.2023.2257348 -
The Science of the Total Environment Nov 2023Agrochemicals represent prominent anthropogenic stressors contributing to the ongoing global insect decline. While their impact is generally assessed in terms of...
Agrochemicals represent prominent anthropogenic stressors contributing to the ongoing global insect decline. While their impact is generally assessed in terms of mortality rates, non-lethal effects on fitness are equally important to insect conservation. Glyphosate, a commonly used herbicide, is toxic to many animal species, and thought to impact a range of physiological functions. In this study, we investigate the impact of long-term exposure to glyphosate on locomotion, phototaxis and learning abilities in bumblebees, using a fully automated high-throughput assay. We find that glyphosate exposure had a very slight and transient impact on locomotion, while leaving the phototactic drive unaffected. Glyphosate exposure also reduced attraction towards UV light when blue was given as an alternative and, most strikingly, impaired learning of aversive stimuli. Thus, glyphosate had specific actions on sensory and cognitive processes. These non-lethal perceptual and cognitive impairments likely represent a significant obstacle to foraging and predator avoidance for wild bumblebees exposed to glyphosate. Similar effects in other species could contribute to a widespread reduction in foraging efficiency across ecosystems, driven by the large-scale application of this herbicide. The high-throughput paradigm presented in this study can be adapted to investigate sublethal effects of other agrochemicals on bumblebees or other important pollinator species, opening up a critical new avenue for the study of anthropogenic stressors.
PubMed: 37451452
DOI: 10.1016/j.scitotenv.2023.165527 -
The Journal of Comparative Neurology Oct 2021In 1994, Burrill and Easter described the retinal projections in embryonic and larval zebrafish, introducing the term "arborization fields" (AFs) for the retinorecipient... (Review)
Review
In 1994, Burrill and Easter described the retinal projections in embryonic and larval zebrafish, introducing the term "arborization fields" (AFs) for the retinorecipient areas. AFs were numbered from 1 to 10 according to their positions along the optic tract. With the exception of AF10 (neuropil of the optic tectum), annotations of AFs remained tentative. Here we offer an update on the likely identities and functions of zebrafish AFs after successfully matching classical neuroanatomy to the digital Max Planck Zebrafish Brain Atlas. In our system, individual AFs are neuropil areas associated with the following nuclei: AF1 with the suprachiasmatic nucleus; AF2 with the posterior parvocellular preoptic nucleus; AF3 and AF4 with the ventrolateral thalamic nucleus; AF4 with the anterior and intermediate thalamic nuclei; AF5 with the dorsal accessory optic nucleus; AF7 with the parvocellular superficial pretectal nucleus; AF8 with the central pretectal nucleus; and AF9d and AF9v with the dorsal and ventral periventricular pretectal nuclei. AF6 is probably part of the accessory optic system. Imaging, ablation, and activation experiments showed contributions of AF5 and potentially AF6 to optokinetic and optomotor reflexes, AF4 to phototaxis, and AF7 to prey detection. AF6, AF8 and AF9v respond to dimming, and AF4 and AF9d to brightening. While few annotations remain tentative, it is apparent that the larval zebrafish visual system is anatomically and functionally continuous with its adult successor and fits the general cyprinid pattern. This study illustrates the synergy created by merging classical neuroanatomy with a cellular-resolution digital brain atlas resource and functional imaging in larval zebrafish.
Topics: Animals; Brain Mapping; Pretectal Region; Retina; Superior Colliculi; Visual Pathways; Zebrafish
PubMed: 34180059
DOI: 10.1002/cne.25204 -
The Science of the Total Environment Mar 2022Environmental contamination by plastics and its negative effect on biodiversity have been well-documented in several types of organisms, especially in marine... (Review)
Review
Environmental contamination by plastics and its negative effect on biodiversity have been well-documented in several types of organisms, especially in marine environments. Therefore, it is necessary to assess the impacts of plastic on other organisms such as aquatic insects, which predominantly inhabit freshwaters. It is widely known that these organisms are sensitive to environmental change, especially by contamination. Therefore, this study aimed at testing the hypothesis that aquatic insects are impacted by plastic contamination. We made a systematic search for international papers related to plastics and aquatic insects in databases such as Google Scholar, Web of Science, and Scopus. We obtained 1217 studies of which 40 discussed the impacts of contamination by plastics on aquatic insects. We identified two main impacts: the first one is caused by the use of black macroplastic to protect crops from contact with the soil in agriculture. These black macroplastics attract tons of adult aquatic insects (terrestrial stage) that mistake the plastic surface for water because they select oviposition sites through phototaxis or polarotaxis. The second one comes from water contamination that can originate from the inadequate disposal of plastics, which harms young aquatic insects (aquatic phase) when they feed, reproduce, and construct shelters. Our results show the negative impacts of plastics on both larvae and adult aquatic insects. Despite the large knowledge gap regarding the impacts of plastic on aquatic insects, the evidence above is sufficient to consider these organisms important in global discussions regarding the impacts of plastic on biodiversity.
Topics: Animals; Aquatic Organisms; Ecosystem; Environmental Monitoring; Fresh Water; Insecta; Plastics; Water Pollutants, Chemical; Water Pollution
PubMed: 34971686
DOI: 10.1016/j.scitotenv.2021.152436 -
Aquatic Toxicology (Amsterdam,... Dec 2023Animal-based sensors have been increasingly applied to many water monitoring systems and ecological studies. One of the staple organisms used as living sensors for such... (Review)
Review
Animal-based sensors have been increasingly applied to many water monitoring systems and ecological studies. One of the staple organisms used as living sensors for such systems is Daphnia. This organism has been extensively studied and, with time, used in many toxicological and pharmaceutical bioassays, often used for exploring the ecology of freshwater communities. One of its behaviours used for evaluating the state of the aquatic environment is phototaxis. A disruption in the predicted behaviour is interpreted as a sign of stress and forms the basis for further investigation. However, phototaxis is a result of complex processes counteracting and interacting with each other. Predator presence, food quality, body pigmentation and other factors can greatly affect the predicted phototactic response, hampering its reliability as a bioindicator. Therefore, a holistic approach and meticulous documentation of the methods are needed for the correct interpretation of this behavioural indicator. In this review, we present the current methods used for studying phototaxis, the factors affecting it and proposed ways to optimise the reliability of the results.
Topics: Animals; Water Pollutants, Chemical; Phototaxis; Reproducibility of Results; Daphnia
PubMed: 38000135
DOI: 10.1016/j.aquatox.2023.106762 -
Acta Biomaterialia Dec 2021Biohybrid microswimmers exploit the natural abilities of motile microorganisms e.g. in releasing cargo on-demand. However, using such engineered swarms to release...
Biohybrid microswimmers exploit the natural abilities of motile microorganisms e.g. in releasing cargo on-demand. However, using such engineered swarms to release antibiotics addressing bacterial infections has not yet been realized. Herein, a design strategy for biohybrid microswimmers is reported, which features the covalent attachment of antibiotics with a photo-cleavable linker to the algae Chlamydomonas reinhardtii via two synthetic steps. This surface engineering does not rely on genetic manipulations, proceeds with high efficiency, and retains the viability or phototaxis of microalgae. Two different antibiotics have been separately utilized, which result in activity against both gram-positive and gram-negative strains. Guiding the biohybrid microswimmers by an external beacon, and on-demand delivery of the drugs by light with high spatial and temporal control, allowed for strong inhibition of bacterial growth. This efficient strategy could potentially allow for the selective treatment of bacterial infections by engineered algal microrobots with high precision in space and time. STATEMENT OF SIGNIFICANCE: Biological swimmers with innate sensing and actuation capabilities and integrated components have been widely investigated to create autonomous microsystems. The use of natural swimmers as cargo delivery systems presents an alternative strategy to transport therapeutics to the required locations with the difficult access by traditional strategies. Although the transfer of various therapeutic cargo has shown promising results, the utilization of microswimmers for the delivery of antimicrobials was barely covered. Therefore, we present biohybrid microalga-powered swimmers designed and engineered to carry antibiotic cargo against both Gram-positive and Gram-negative bacteria. Guided by an external beacon, these microhybrids deliver the antibiotic payload to the site of bacterial infection, with high spatial and temporal precision, released on-demand by an external trigger to inhibit bacterial growth.
Topics: Anti-Bacterial Agents; Bacterial Infections; Gram-Negative Bacteria; Gram-Positive Bacteria; Humans
PubMed: 34601106
DOI: 10.1016/j.actbio.2021.09.048 -
Microbial Cell (Graz, Austria) Jan 2020The microbial environment is typically within a fluid and the key processes happen at the microscopic scale where viscosity dominates over inertial forces. Microfluidic... (Review)
Review
The microbial environment is typically within a fluid and the key processes happen at the microscopic scale where viscosity dominates over inertial forces. Microfluidic tools are thus well suited to study microbial motility because they offer precise control of spatial structures and are ideal for the generation of laminar fluid flows with low Reynolds numbers at microbial lengthscales. These tools have been used in combination with microscopy platforms to visualise and study various microbial taxes. These include establishing concentration and temperature gradients to influence motility via chemotaxis and thermotaxis, or controlling the surrounding microenvironment to influence rheotaxis, magnetotaxis, and phototaxis. Improvements in microfluidic technology have allowed fine separation of cells based on subtle differences in motility traits and have applications in synthetic biology, directed evolution, and applied medical microbiology.
PubMed: 32161767
DOI: 10.15698/mic2020.03.710 -
Biochemistry. Biokhimiia Jan 2020Proteins of the cryptochrome/DNA photolyase family (CPF) are phylogenetically related and structurally conserved flavoproteins that perform various functions. DNA... (Review)
Review
Proteins of the cryptochrome/DNA photolyase family (CPF) are phylogenetically related and structurally conserved flavoproteins that perform various functions. DNA photolyases repair DNA damage caused by UV-B radiation by exposure to UV-A/blue light simultaneously or subsequently. Cryptochromes are photoreceptor proteins regulating circadian clock, morphogenesis, phototaxis, and other responses to UV and blue light in various organisms. The review describes the structure and functions of CPF proteins, their evolutionary relationship, and possible functions of the CPF ancestor protein.
Topics: Animals; Circadian Clocks; Cryptochromes; DNA Damage; DNA Repair; DNA-Binding Proteins; Deoxyribodipyrimidine Photo-Lyase; Evolution, Molecular; Humans; Phylogeny; Protein Conformation, alpha-Helical; Ultraviolet Rays
PubMed: 32087057
DOI: 10.1134/S0006297920140072 -
Frontiers in Neural Circuits 2021Visual processing transforms the complexities of the visual world into useful information. , an invertebrate chordate and close relative of the vertebrates, has one of...
Visual processing transforms the complexities of the visual world into useful information. , an invertebrate chordate and close relative of the vertebrates, has one of the simplest nervous systems known, yet has a range of visuomotor behaviors. This simplicity has facilitated studies linking behavior and neural circuitry. larvae have two distinct visuomotor behaviors - a looming shadow response and negative phototaxis. These are mediated by separate neural circuits that initiate from different clusters of photoreceptors, with both projecting to a CNS structure called the posterior brain vesicle (pBV). We report here that inputs from both circuits are processed to generate fold change detection (FCD) outputs. In FCD, the behavioral response scales with the relative fold change in input, but is invariant to the overall magnitude of the stimulus. Moreover, the two visuomotor behaviors have fundamentally different stimulus/response relationships - indicative of differing circuit strategies, with the looming shadow response showing a power relationship to fold change, while the navigation behavior responds linearly. Pharmacological modulation of the FCD response points to the FCD circuits lying outside of the visual organ (the ocellus), with the pBV being the most likely location. Consistent with these observations, the connectivity and properties of pBV interneurons conform to known FCD circuit motifs, but with different circuit architectures for the two circuits. The negative phototaxis circuit forms a putative incoherent feedforward loop that involves interconnecting cholinergic and GABAergic interneurons. The looming shadow circuit uses the same cholinergic and GABAergic interneurons, but with different synaptic inputs to create a putative non-linear integral feedback loop. These differing circuit architectures are consistent with the behavioral outputs of the two circuits. Finally, while some reports have highlighted parallels between the pBV and the vertebrate midbrain, suggesting a common origin for the two, others reports have disputed this, suggesting that invertebrate chordates lack a midbrain homolog. The convergence of visual inputs at the pBV, and its putative role in visual processing reported here and in previous publications, lends further support to the proposed common origin of the pBV and the vertebrate midbrain.
Topics: Animals; Central Nervous System; Interneurons; Larva; Vertebrates; Visual Perception
PubMed: 34497492
DOI: 10.3389/fncir.2021.705161 -
Journal of Basic Microbiology Oct 2022Light plays a crucial role in photosynthesis, photoperiodism, and photomorphogenesis. Algae have a specialized visual system to perceive the light signal known as... (Review)
Review
Light plays a crucial role in photosynthesis, photoperiodism, and photomorphogenesis. Algae have a specialized visual system to perceive the light signal known as eyespot. A typical eyespot is an orange-colored, membranous structure packed with pigmented granules. In algae, the eyespot membrane bears a specialized type of photoreceptors, which shows similarity with animal rhodopsin photoreceptors. This light-sensing receptor is responsible for the photo-mobility response known as phototaxis. In this, light acts as a signal for onset and cascade of downstream signal transduction pathway leading to a conformational change in photoreceptor. This induces the continuous influx of calcium ions through the opening of calcium ion channels leading to membrane depolarization, and beating of flagella which is responsible for phototaxis. Mutational studies have assisted the discovery of eyespot genes, which are involved in eyespot development, assembly, size control, and functioning in Chlamydomonas. These genes belong to photoreceptors (cop1-12, acry, pcry, cry-dash1, cry-dash2, phot, uvr8), eyeless mutants (eye2, eye3), miniature-eyespot mutants (min1, min2), multiple eyespot mutants (mlt1, mlt2). This review discusses the structural biology of eyespots with special reference to Chlamydomonas, molecular insights, related genes, and proteins responsible for its proper functioning.
Topics: Animals; Calcium; Calcium Channels; Chlamydomonas; Chlamydomonas reinhardtii; Light; Rhodopsin
PubMed: 35778815
DOI: 10.1002/jobm.202200249