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Proceedings of the National Academy of... Dec 2018Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This...
Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed "phototaxis," enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium sp. strain PCC 6803, but the rod-shaped PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of , the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJ (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Plate-based phototaxis assays indicate that UTEX 3055 uses PixJ to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJ controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in .
Topics: Amino Acid Sequence; Bacterial Proteins; Biofilms; Cyanobacteria; Gene Expression Regulation, Bacterial; Photoreceptors, Microbial; Phototaxis; Synechococcus; Synechocystis
PubMed: 30552139
DOI: 10.1073/pnas.1812871115 -
The Journal of General and Applied... Jun 2021Phototaxis is a phenomenon where cyanobacteria move toward a light source. Previous studies have shown that the blue-light-using-flavin (BLUF)-type photoreceptor PixD...
Phototaxis is a phenomenon where cyanobacteria move toward a light source. Previous studies have shown that the blue-light-using-flavin (BLUF)-type photoreceptor PixD and the response regulator-like protein PixE control the phototaxis in the cyanobacterium Synechocystis sp. PCC 6803. The pixD-null mutant moves away from light, whereas WT, pixE mutant, and pixD pixE double mutant move toward the light. This indicates that PixE functions downstream of PixD and influences the direction of movement. However, it is still unclear how the light signal received by PixD is transmitted to PixE, and then subsequently transmitted to the type IV pili motor mechanism. Here, we investigated intracellular localization and oligomerization of PixD and PixE to elucidate mechanisms of phototaxis regulation. Blue-native PAGE analysis, coupled with western blotting, indicated that most PixD exist as a dimer in soluble fractions, whereas PixE localized in ~250 kDa and ~450 kDa protein complexes in membrane fractions. When blue-native PAGE was performed after illuminating the membrane fractions with blue light, PixE levels in the ~250 kDa and ~450 kDa complexes were reduced and increased, respectively. These results suggest that PixE, localized in the ~450 kDa complex, controls activity of the motor ATPase PilB1 to regulate pilus motility.
Topics: Bacterial Proteins; Cell Membrane; Light; Light Signal Transduction; Models, Biological; Mutation; Photoreceptors, Microbial; Phototaxis; Protein Multimerization; Synechocystis
PubMed: 33342920
DOI: 10.2323/jgam.2020.06.001 -
Journal of the Royal Society, Interface Mar 2015Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator, and as the cell rotates during the forward motion, the light signal...
Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator, and as the cell rotates during the forward motion, the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model, and the steering mechanism is robust to noise. Our model shows switching between directed phototaxis when the light is on and run-and-tumble behaviour in the dark.
Topics: Algorithms; Biophysics; Chlamydomonas; Flagella; Light; Models, Biological; Movement; Reproducibility of Results
PubMed: 25589576
DOI: 10.1098/rsif.2014.1164 -
The Science of the Total Environment Jul 2022Animal behavioural responses are increasingly being used in environmental risk assessment. Nevertheless, behavioural responses are still hampered by a lack of...
Animal behavioural responses are increasingly being used in environmental risk assessment. Nevertheless, behavioural responses are still hampered by a lack of standardisation. Phototactic behaviour in zooplankton and in particular in Daphnia has often been associated to vertical migration but there is also 'shore-avoidance' horizontal behaviour: Daphnia uses shades along the shore to swim either to or away from the shore and predators. Previously, we develop a vertical oriented behavioural hardware able to reproduce phototactic fish induced depth selection in Daphnia magna, its modulation by fish kairomones and psychotropic drugs and the neurotransmitter profiles associated to those responses. This study aims to test if it is possible to use an horizontal 24 multi-well plate maze set up to assess phototactic fish induced responses in D. magna. The study was conducted using two clones with opposed phototaxis upon exposure to fish kairomones and using psychotropic drugs known to modulate phototaxis. Acrylic strips opaque to visible light but not to the infrared one were used to cover half of the arena of each of the wells of the multi-well plate. Clone P32,85 showed positive phototaxis in either the vertical and horizontal set up and negative phototaxis when exposed to fish kairomones or to the muscarinic acetylcholine receptor antagonist's scopolamine and atropine. The opposite behaviour was observed for clone F. Diazepam and pilocarpine ameliorate fish kairomone induced negative phototaxis and picrotoxin increased it only in clone P32,85 in the vertical set up. The determination of neurotransmitters showed much greater concentrations of dopamine and of glycine in clone F, which may be relate to its negative phototaxis and its observed lower responsiveness to fish kairomones. The results from this study suggest a simple, fast, and high throughput phototactic behaviour assay for D. magna that can be easily adapted to other species.
Topics: Animals; Clone Cells; Daphnia; Fishes; Neurotransmitter Agents; Pheromones; Phototaxis; Psychotropic Drugs
PubMed: 35314222
DOI: 10.1016/j.scitotenv.2022.154684 -
Frontiers in Plant Science 2019The green algae is a model system for motility in unicellular organisms. Photo-, gravi-, and chemotaxis have previously been associated with , and observing the extent...
The green algae is a model system for motility in unicellular organisms. Photo-, gravi-, and chemotaxis have previously been associated with , and observing the extent of these responses within a population of cells is crucial for refining our understanding of how this organism responds to changing environmental conditions. However, manually tracking and modeling a statistically viable number of samples of these microorganisms is an unreasonable task. We hypothesized that automated particle tracking systems are now sufficiently advanced to effectively characterize such populations. Here, we present an automated method to observe motility that allows us to identify individual cells as well as global information on direction, speed, and size. Nutrient availability effects on wild-type swimming speeds, as well as changes in speed and directionality in response to light, were characterized using this method. We also provide for the first time the swimming speeds of several motility-deficient mutant lines. While our present effort is focused around the unicellular green algae, , we confirm the general utility of this approach using , another member of this genus which contains over 300 species. Our work provides new tools for evaluating and modeling motility in this model organism and establishes the methodology for conducting similar experiments on other unicellular microorganisms.
PubMed: 32076424
DOI: 10.3389/fpls.2019.01616 -
Light-induced chromophore and protein responses and mechanical signal transduction of BLUF proteins.Biophysical Reviews Apr 2018Photoreceptor proteins have been used to study how protein conformational changes are induced by alterations in their environments and how their signals are transmitted... (Review)
Review
Photoreceptor proteins have been used to study how protein conformational changes are induced by alterations in their environments and how their signals are transmitted to downstream factors to dictate physiological responses. These proteins are attractive models because their signal transduction aspects and structural changes can be precisely regulated in vivo and in vitro based on light intensity. Among the known photoreceptors, members of the blue light-using flavin (BLUF) protein family have been well characterized with regard to how they control various light-dependent physiological responses in several microorganisms. Herein, we summarize our current understanding of their photoactivation and signal-transduction mechanisms. For signal transduction, we review recent studies concerning how the BLUF protein, PixD, transmits a light-induced signal to its downstream factor, PixE, to modulate phototaxis of the cyanobacterium Synechocystis sp. PCC6803.
PubMed: 29235080
DOI: 10.1007/s12551-017-0355-6 -
Biochemistry. Biokhimiia Nov 2001Green flagellate algae are capable of the active adjustment of their swimming path according to the light direction (phototaxis). This direction is detected by a special... (Review)
Review
Green flagellate algae are capable of the active adjustment of their swimming path according to the light direction (phototaxis). This direction is detected by a special photoreceptor apparatus consisting of the photoreceptor membrane and eyespot. Receptor photoexcitation in green flagellates triggers a cascade of rapid electrical events in the cell membrane which plays a crucial role in the signal transduction chain of phototaxis and the photophobic response. The photoreceptor current is the earliest so far detectable process in this cascade. Measurement of the photoreceptor current is at present the most suitable approach to investigation of the photoreceptor pigment in green flagellate algae, since a low receptor concentration in the cell makes application of optical and biochemical methods so far impossible. A set of physiological evidences shows that the phototaxis receptor in green flagellate algae is a unique rhodopsin-type protein. It shares common chromophore properties with retinal proteins from archaea. However, the involvement of photoelectric processes in the signal transduction chain relates it to animal visual rhodopsins. The presence of some enzymatic components of the animal visual cascade in isolated eyespot preparations might also point to this relation. A retinal-binding protein has been identified in such preparations, the amino acid sequence of which shows a certain homology to sequences of animal visual rhodopsins. However, potential function of this protein as the phototaxis receptor has been questioned in recent time.
Topics: Chlorophyta; Light; Receptors, Cell Surface; Rhodopsin; Signal Transduction
PubMed: 11743874
DOI: 10.1023/a:1013191504508 -
BMC Biology May 2022Mosquitoes locate a human host by integrating various sensory cues including odor, thermo, and vision. However, their innate light preference and its genetic basis that...
BACKGROUND
Mosquitoes locate a human host by integrating various sensory cues including odor, thermo, and vision. However, their innate light preference and its genetic basis that may predict the spatial distribution of mosquitoes, a prerequisite to encounter a potential host and initiate host-seeking behaviors, remains elusive.
RESULTS
Here, we first studied mosquito visual features and surprisingly uncovered that both diurnal (Aedes aegypti and Aedes albopictus) and nocturnal (Culex quinquefasciatus) mosquitoes significantly avoided stronger light when given choices. With consistent results from multiple assays, we found that such negative phototaxis maintained throughout development to adult stages. Notably, female mosquitoes significantly preferred to bite hosts in a shaded versus illuminated area. Furthermore, silencing Opsin1, a G protein-coupled receptor that is most enriched in compound eyes, abolished light-evoked avoidance behavior of Aedes albopictus and attenuated photonegative behavior in Aedes aegypti. Finally, we found that field-collected Aedes albopictus also prefers darker area in an Opsin1-dependent manner.
CONCLUSIONS
This study reveals that mosquitoes consistently prefer darker environment and identifies the first example of a visual molecule that modulates mosquito photobehavior.
Topics: Aedes; Animals; Avoidance Learning; Culex; Feeding Behavior; Female; Humans
PubMed: 35549721
DOI: 10.1186/s12915-022-01308-0 -
International Journal of Molecular... Mar 2022is a photosynthetic flagellate. To acquire a suitable position in its surrounding aquatic environment, it exploits light and gravity primarily as environmental cues....
is a photosynthetic flagellate. To acquire a suitable position in its surrounding aquatic environment, it exploits light and gravity primarily as environmental cues. Several physiological studies have indicated a fine-tuned relationship between gravity sensing (gravitaxis) and light sensing in . However, the underlying molecular mechanism is largely unknown. The photoreceptor photoactivated adenylyl cyclase (PAC) has been studied for over a decade. Nevertheless, no direct/indirect interaction partner (upstream/downstream) has been reported for PAC. It has been shown that a specific protein, kinase A (PKA), showed to be involved in phototaxis and gravitaxis. The current study reports the localization of the specific PKA and its relationship with PAC.
Topics: Adenylyl Cyclases; Euglena gracilis; Gravitation; Photoreceptor Cells; Phototaxis
PubMed: 35269918
DOI: 10.3390/ijms23052776 -
Molecular Microbiology Aug 2004Many photosynthetic microorganisms have evolved the ability to sense light quality and/or quantity and can steer themselves into optimal conditions within the... (Review)
Review
Many photosynthetic microorganisms have evolved the ability to sense light quality and/or quantity and can steer themselves into optimal conditions within the environment. Phototaxis and gliding motility in unicellular cyanobacteria require type IV pili, which are multifunctional cell surface appendages. Screens for cells exhibiting aberrant motility uncovered several non-motile mutants as well as some that had lost positive phototaxis (consequently, they were negatively phototactic). Several negatively phototactic mutants mapped to the tax1 locus, which contains five chemotaxis-like genes. This locus includes a gene that encodes a putative photoreceptor (TaxD1) for positive phototaxis. A second chemotaxis-like cluster (tax3 locus) appears to be involved in pilus biogenesis. The biosynthesis and regulation of type IV pilus-based motility as well as the communication between the pilus motor and photosensory molecules appear to be complex and tightly regulated. Furthermore, the discovery that cyclic AMP and novel gene products are necessary for phototaxis/motility suggests that there might be additional levels of communication and signal processing.
Topics: Bacterial Proteins; Chemotaxis; Cyanobacteria; Escherichia coli; Flagella; Light; Movement; Signal Transduction
PubMed: 15255889
DOI: 10.1111/j.1365-2958.2004.04160.x