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Plant Physiology Apr 2023The eyespot apparatus is an organelle that forms carotenoid-rich globules in diverse flagellated microalgae and functions in phototaxis. The euglenophytes have...
The eyespot apparatus is an organelle that forms carotenoid-rich globules in diverse flagellated microalgae and functions in phototaxis. The euglenophytes have structurally and functionally distinct eyespot apparatuses from chlorophytes. β-Carotene is the most abundant pigment detected in chlorophytes' eyespots, while xanthophylls such as zeaxanthin and diadinoxanthin have been suggested to function in euglenophytes' eyespots. Here, we investigated the association between carotenoid composition and eyespot formation via pathway-scale mutagenesis using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome editing in the euglenophyte Euglena gracilis. Lycopene cyclase (lcy) mutants exhibited sole lycopene accumulation, defective red eyespots, and phototactic insensitivity. Conversely, β-carotene hydroxylase (cytochrome P450 97h1, cyp97h1) mutants accumulated β-carotene and its hydroxylated products β-cryptoxanthin and zeaxanthin and formed phototactic eyespot apparatuses, while cyp97h1 cyp97f2 double mutants were deficient in β-carotene hydroxylation and mostly lacked functional eyespots. Thus, zeaxanthin is required for the stable formation of functional eyespots in E. gracilis, highlighting evolutionary differences between euglenophytes and chlorophytes in the metabolic regulation of photoreactive organelle formation.
Topics: Zeaxanthins; beta Carotene; Euglena gracilis; Phototaxis; Carotenoids; Organelles; Cytochrome P-450 Enzyme System
PubMed: 36611254
DOI: 10.1093/plphys/kiad001 -
International Journal of Molecular... Dec 2012Ultraviolet (UV) radiation can cause stresses or act as a photoregulatory signal depending on its wavelengths and fluence rates. Although the most harmful effects of UV... (Review)
Review
Ultraviolet (UV) radiation can cause stresses or act as a photoregulatory signal depending on its wavelengths and fluence rates. Although the most harmful effects of UV on living cells are generally attributed to UV-B radiation, UV-A radiation can also affect many aspects of cellular processes. In cyanobacteria, most studies have concentrated on the damaging effect of UV and defense mechanisms to withstand UV stress. However, little is known about the activation mechanism of signaling components or their pathways which are implicated in the process following UV irradiation. Motile cyanobacteria use a very precise negative phototaxis signaling system to move away from high levels of solar radiation, which is an effective escape mechanism to avoid the detrimental effects of UV radiation. Recently, two different UV-A-induced signaling systems for regulating cyanobacterial phototaxis were characterized at the photophysiological and molecular levels. Here, we review the current understanding of the UV-A mediated signaling pathways in the context of the UV-A perception mechanism, early signaling components, and negative phototactic responses. In addition, increasing evidences supporting a role of pterins in response to UV radiation are discussed. We outline the effect of UV-induced cell damage, associated signaling molecules, and programmed cell death under UV-mediated oxidative stress.
Topics: Cryptochromes; Cyanobacteria; Light Signal Transduction; Oxidative Stress; Pterins; Reactive Oxygen Species; Signal Transduction; Ultraviolet Rays
PubMed: 23208372
DOI: 10.3390/ijms131216303 -
Philosophical Transactions of the Royal... Dec 2015The origin of nervous systems has traditionally been discussed within two conceptual frameworks. Input-output models stress the sensory-motor aspects of nervous systems,... (Review)
Review
The origin of nervous systems has traditionally been discussed within two conceptual frameworks. Input-output models stress the sensory-motor aspects of nervous systems, while internal coordination models emphasize the role of nervous systems in coordinating multicellular activity, especially muscle-based motility. Here we consider both frameworks and apply them to describe aspects of each of three main groups of phenomena that nervous systems control: behaviour, physiology and development. We argue that both frameworks and all three aspects of nervous system function need to be considered for a comprehensive discussion of nervous system origins. This broad mapping of the option space enables an overview of the many influences and constraints that may have played a role in the evolution of the first nervous systems.
Topics: Animals; Biological Evolution; Motor Activity; Nervous System; Nervous System Physiological Phenomena
PubMed: 26554049
DOI: 10.1098/rstb.2015.0181 -
Extremophiles : Life Under Extreme... Jan 2020Recent progress in extremophile biology, exploration of planetary bodies in the solar system, and the detection and characterization of extrasolar planets are leading to... (Review)
Review
Recent progress in extremophile biology, exploration of planetary bodies in the solar system, and the detection and characterization of extrasolar planets are leading to new insights in the field of astrobiology and possible distribution of life in the universe. Among the many extremophiles on Earth, the halophilic Archaea (Haloarchaea) are especially attractive models for astrobiology, being evolutionarily ancient and physiologically versatile, potentially surviving in a variety of planetary environments and with relevance for in situ life detection. Haloarchaea are polyextremophilic with tolerance of saturating salinity, anaerobic conditions, high levels of ultraviolet and ionizing radiation, subzero temperatures, desiccation, and toxic ions. Haloarchaea survive launches into Earth's stratosphere encountering conditions similar to those found on the surface of Mars. Studies of their unique proteins are revealing mechanisms permitting activity and function in high ionic strength, perchlorates, and subzero temperatures. Haloarchaea also produce spectacular blooms visible from space due to synthesis of red-orange isoprenoid carotenoids used for photoprotection and photorepair processes and purple retinal chromoproteins for phototrophy and phototaxis. Remote sensing using visible and infrared spectroscopy has shown that haloarchaeal pigments exhibit both a discernable peak of absorption and a reflective "green edge". Since the pigments produce remotely detectable features, they may influence the spectrum from an inhabited exoplanet imaged by a future large space-based telescope. In this review, we focus primarily on studies of two Haloarchaea, Halobacterium sp. NRC-1 and Halorubrum lacusprofundi.
Topics: Exobiology; Extremophiles; Halobacterium; Halorubrum; Remote Sensing Technology
PubMed: 31463573
DOI: 10.1007/s00792-019-01126-3 -
Neuroscience Letters Jan 2022Ultraviolet light is quite toxic to all the animals and evoke the avoidance behavior of UV. The soil nematode Caenorhabditis elegans senses UV and is known to avoid UV...
Ultraviolet light is quite toxic to all the animals and evoke the avoidance behavior of UV. The soil nematode Caenorhabditis elegans senses UV and is known to avoid UV by using four sensory neurons. However, it is not clear what signaling molecules act for UV avoidance in the neuronal pathway constituted of four sensory neurons. In addition, it is not clear whether this harmful environmental signal can be associated with other benefit signals such as food. In this study, by using newly developed assay system, we found that C. elegans can associate UV and food and changes behavioral strategy against harmful UV signal. This is the first indication that C. elegans shows associate learning with UV and food. Using our assay system, we also found that glutamate is used as a transmitter in both the UV avoidance and UV associate learning neural circuits. However, one sensory neuron showed a significant role for associative learning, compared to a complimentary role in four sensory neurons for direct associative learning, and different sets of glutamate receptors seemed to be acting for UV avoidance and UV associate learning. These findings suggest that a distinct neuronal network is used for UV learning compared to that for direct avoidance behavior of UV.
Topics: Animals; Caenorhabditis elegans; Feeding Behavior; Glutamic Acid; Learning; Neuronal Plasticity; Phototaxis; Receptors, Glutamate; Sensory Receptor Cells; Ultraviolet Rays
PubMed: 34890717
DOI: 10.1016/j.neulet.2021.136384 -
Molecular Biology and Evolution May 2021Anthozoan corals are an ecologically important group of cnidarians, which power the productivity of reef ecosystems. They are sessile, inhabit shallow, tropical oceans... (Comparative Study)
Comparative Study
Anthozoan corals are an ecologically important group of cnidarians, which power the productivity of reef ecosystems. They are sessile, inhabit shallow, tropical oceans and are highly dependent on sun- and moonlight to regulate sexual reproduction, phototaxis, and photosymbiosis. However, their exposure to high levels of sunlight also imposes an increased risk of UV-induced DNA damage. How have these challenging photic environments influenced photoreceptor evolution and function in these animals? To address this question, we initially screened the cnidarian photoreceptor repertoire for Anthozoa-specific signatures by a broad-scale evolutionary analysis. We compared transcriptomic data of more than 36 cnidarian species and revealed a more diverse photoreceptor repertoire in the anthozoan subphylum than in the subphylum Medusozoa. We classified the three principle opsin classes into distinct subtypes and showed that Anthozoa retained all three classes, which diversified into at least six subtypes. In contrast, in Medusozoa, only one class with a single subtype persists. Similarly, in Anthozoa, we documented three photolyase classes and two cryptochrome (CRY) classes, whereas CRYs are entirely absent in Medusozoa. Interestingly, we also identified one anthozoan CRY class, which exhibited unique tandem duplications of the core functional domains. We next explored the functionality of anthozoan photoreceptors in the model species Exaiptasia diaphana (Aiptasia), which recapitulates key photo-behaviors of corals. We show that the diverse opsin genes are differentially expressed in important life stages common to reef-building corals and Aiptasia and that CRY expression is light regulated. We thereby provide important clues linking coral evolution with photoreceptor diversification.
Topics: Animals; Anthozoa; Biological Evolution; Cryptochromes; Opsins; Photoreceptor Cells, Invertebrate
PubMed: 33226083
DOI: 10.1093/molbev/msaa304 -
Bio-protocol Jun 2017Phototaxis is a behavior in which organisms move toward or away from the light source (positive or negative phototaxis, respectively). It is crucial for phototrophic...
Phototaxis is a behavior in which organisms move toward or away from the light source (positive or negative phototaxis, respectively). It is crucial for phototrophic microorganisms to inhabit under proper light conditions for phototaxis. The unicellular green alga rapidly changes its swimming direction upon light illumination, and thus is a nice model organism for phototaxis research. Here we show two methods to assay phototaxis; one is a quick, easy and qualitative analysis, so-called the dish assay; and the other is a quantitative single-cell analysis.
PubMed: 34541103
DOI: 10.21769/BioProtoc.2356 -
Current Opinion in Neurobiology Oct 2015Sensory signals are processed in the brain by dedicated neuronal circuits to form perceptions used to guide behavior. Drosophila, with its compact brain, amenability to... (Review)
Review
Sensory signals are processed in the brain by dedicated neuronal circuits to form perceptions used to guide behavior. Drosophila, with its compact brain, amenability to genetic manipulations and sophisticated behaviors has emerged as a powerful model for investigating the neuronal circuits responsible for sensory perception. Vision in particular has been examined in detail. Light is detected in the eye by photoreceptors, specialized neurons containing light sensing Rhodopsin proteins. These photoreceptor signals are relayed to the optic lobes where they are processed to gain perceptions about different properties of the visual scene. In this review we describe recent advances in the characterization of neuronal circuits underlying four visual modalities in the fly brain: motion vision, phototaxis, color and polarized light vision.
Topics: Animals; Drosophila; Nerve Net; Photic Stimulation; Signal Transduction; Vision, Ocular; Visual Pathways; Visual Perception
PubMed: 25881091
DOI: 10.1016/j.conb.2015.03.010 -
Biology Letters Jan 2022Behavioural immunity describes suites of behaviours hosts use to minimize the risks of infection by parasites/pathogens. Research has focused primarily on the evasion...
Behavioural immunity describes suites of behaviours hosts use to minimize the risks of infection by parasites/pathogens. Research has focused primarily on the evasion and physical removal of infectious stages, as well as behavioural fever. However, other behaviours affect infection risk while carrying ecologically significant trade-offs. Phototaxis, in particular, has host fitness implications (e.g. altering feeding and thermoregulation) that also impact infection outcomes. In this study, we hypothesized that a fly host, , employs phototaxis as a form of behavioural immunity to reduce the risk of infection. First, we determined that the risk of infection is lower for flies exposed in the light relative to the dark using micro-arena experiments. Because vary in ectoparasite resistance based on mating status we examined parasite-mediated phototaxis in mated and unmated females. We found that female flies spent more time in the light side of phototaxis chambers when mites were present than in the absence of mites. Mating marginally decreased female photophobia independently of mite exposure. Female flies moved to lighter, i.e. less infectious, environments when threatened with mites, suggesting phototaxis is a mechanism of behavioural immunity. We discuss how parasite-mediated phototaxis potentially trades-off with host nutrition and thermoregulation.
Topics: Animals; Drosophila; Female; Host-Parasite Interactions; Mites; Parasites; Phototaxis
PubMed: 35078333
DOI: 10.1098/rsbl.2021.0531 -
The Journal of Cell Biology Nov 1973Parameters which distinguish phototaxis from random motility in Chlamydomonas reinhardtii have been defined with quantitative assays. The phototactic responses in...
Parameters which distinguish phototaxis from random motility in Chlamydomonas reinhardtii have been defined with quantitative assays. The phototactic responses in photosynthetic, mixotrophic, and heterotrophic cultures were highest during exponential growth and declined rapidly as the cultures entered stationary phase. In contrast, random motility was relatively constant throughout growth. Phototaxis and motility also differ in their sensitivity to azide and antimycin A. Both of these drugs inhibited phototaxis within 5 min, but motility was unaffected for at least 30 min. Phototaxis and motility have different ion requirements. Optimum motility was observed in the presence of either Ca(++) or Mg(++); phototaxis required Ca(++) and either K(+) or NH(4) (+). Photosynthesis is not required for phototaxis, since phototaxis was not inhibited by dichlorophenyldimethyl urea, and a mutant lacking chlorophyll was phototactic.
Topics: Antimetabolites; Arginine; Carbon Dioxide; Cell Division; Cell Movement; Chlamydomonas; Cycloheximide; Dinitrophenols; Diuron; Light; Mathematics; Photosynthesis; Plant Proteins; Time Factors
PubMed: 4805005
DOI: 10.1083/jcb.59.2.367