Showing 121 - 130 of 257 Items
Hedgehog signaling is required at multiple stages of zebrafish tooth development
Date: 2010-12-02
Creator: William R. Jackman, James J. Yoo, David W. Stock
Access: Open access
- Background. The accessibility of the developing zebrafish pharyngeal dentition makes it an advantageous system in which to study many aspects of tooth development from early initiation to late morphogenesis. In mammals, hedgehog signaling is known to be essential for multiple stages of odontogenesis; however, potential roles for the pathway during initiation of tooth development or in later morphogenesis are incompletely understood. Results. We have identified mRNA expression of the hedgehog ligands shha and the receptors ptc1 and ptc2 during zebrafish pharyngeal tooth development. We looked for, but did not detect, tooth germ expression of the other known zebrafish hedgehog ligands shhb, dhh, ihha, or ihhb, suggesting that as in mammals, only Shh participates in zebrafish tooth development. Supporting this idea, we found that morphological and gene expression evidence of tooth initiation is eliminated in shha mutant embryos, and that morpholino antisense oligonucleotide knockdown of shha, but not shhb, function prevents mature tooth formation. Hedgehog pathway inhibition with the antagonist compound cyclopamine affected tooth formation at each stage in which we applied it: arresting development at early stages and disrupting mature tooth morphology when applied later. These results suggest that hedgehog signaling is required continuously during odontogenesis. In contrast, over-expression of shha had no effect on the developing dentition, possibly because shha is normally extensively expressed in the zebrafish pharyngeal region. Conclusion. We have identified previously unknown requirements for hedgehog signaling for early tooth initiation and later morphogenesis. The similarity of our results with data from mouse and other vertebrates suggests that despite gene duplication and changes in the location of where teeth form, the roles of hedgehog signaling in tooth development have been largely conserved during evolution. © 2010 Jackman et al; licensee BioMed Central Ltd.
Responses of stomatal features and photosynthesis to porewater N enrichment and elevated atmospheric CO2 in Phragmites australis, the common reed
Date: 2021-04-01
Creator: Julian R. Garrison, Joshua S. Caplan, Vladimir Douhovnikoff, Thomas J. Mozdzer, Barry A. Logan
Access: Open access
- PREMISE: Biological invasions increasingly threaten native biodiversity and ecosystem services. One notable example is the common reed, Phragmites australis, which aggressively invades North American salt marshes. Elevated atmospheric CO2 and nitrogen pollution enhance its growth and facilitate invasion because P. australis responds more strongly to these enrichments than do native species. We investigated how modifications to stomatal features contribute to strong photosynthetic responses to CO2 and nitrogen enrichment in P. australis by evaluating stomatal shifts under experimental conditions and relating them to maximal stomatal conductance (gwmax) and photosynthetic rates. METHODS: Plants were grown in situ in open-top chambers under ambient and elevated atmospheric CO2 (eCO2) and porewater nitrogen (Nenr) in a Chesapeake Bay tidal marsh. We measured light-saturated carbon assimilation rates (Asat) and stomatal characteristics, from which we calculated gwmax and determined whether CO2 and Nenr altered the relationship between gwmax and Asat. RESULTS: eCO2 and Nenr enhanced both gwmax and Asat, but to differing degrees; gwmax was more strongly influenced by Nenr through increases in stomatal density while Asat was more strongly stimulated by eCO2. There was a positive relationship between gwmax and Asat that was not modified by eCO2 or Nenr, individually or in combination. CONCLUSIONS: Changes in stomatal features co-occur with previously described responses of P. australis to eCO2 and Nenr. Complementary responses of stomatal length and density to these global change factors may facilitate greater stomatal conductance and carbon gain, contributing to the invasiveness of the introduced lineage.
The tyrosine kinase Abl and its substrate enabled collaborate with the receptor phosphatase Dlar to control motor axon guidance
Date: 1999-01-01
Creator: Zachary Wills, Jack Bateman, Christopher A. Korey, Allen Comer, David, Van Vactor
Access: Open access
- Genetic analysis of growth cone guidance choice points in Drosophila identified neuronal receptor protein tyrosine phosphatases (RPTPs) as key determinants of axon pathfinding behavior. We now demonstrate that the Drosophila Abl tyrosine kinase functions in the intersegmental nerve b (ISNb) motor choice point pathway as an antagonist of the RPTP Dlar. The function of Abl in this pathway is dependent on an intact catalytic domain. We also show that the Abl phosphoprotein substrate Enabled (Ena) is required for choice point navigation. Both Abl and Ena proteins associate with the Dlar cytoplasmic domain and serve as substrates for Dlar in vitro, suggesting that they play a direct role in the Dlar pathway. These data suggest that Dlar, Abl, and Ena define a phosphorylation state-dependent switch that controls growth cone behavior by transmitting signals at the cell surface to the actin cytoskeleton.
The twin spot generator for differential Drosophila lineage analysis
Date: 2009-07-28
Creator: Ruth Griffin, Anne Sustar, Marianne Bonvin, Richard Binari, Alberto, del Valle Rodriguez, Amber M. Hohl, Jack R. Bateman, Christians Villalta, Elleard Heffern, Didier Grunwald, Chris Bakal, Claude Desplan, Gerold Schubiger, C. Ting Wu, Norbert Perrimon
Access: Open access
- In Drosophila melanogaster, widely used mitotic recombination-based strategies generate mosaic flies with positive readout for only one daughter cell after division. To differentially label both daughter cells, we developed the twin spot generator (TSG) technique, which through mitotic recombination generates green and red twin spots that are detectable after the first cell division as single cells. We propose wide applications of TSG to lineage and genetic mosaic studies.
The first formed tooth serves as a signalling centre to induce the formation of the dental row in zebrafish
Date: 2019-06-12
Creator: Yann Gibert, Eric Samarut, Megan K. Ellis, William R. Jackman, Vincent, Laudet
Access: Open access
- The diversity of teeth patterns in actinopterygians is impressive with tooth rows in many locations in the oral and pharyngeal regions. The first-formed tooth has been hypothesized to serve as an initiator controlling the formation of the subsequent teeth. In zebrafish, the existence of the first tooth (named 4 V1) is puzzling as its replacement is induced before the opening of the mouth. Functionally, it has been shown that 4 V1 formation requires fibroblast growth factor (FGF) and retinoic acid (RA) signalling. Here, we show that the ablation of 4 V1 prevents the development of the dental row demonstrating its dependency over it. If endogenous levels of FGF and RA are restored after 4 V1 ablation, embryonic dentition starts again by de novo formation of a first tooth, followed by the dental row. Similarly, induction of anterior ectopic teeth induces subsequent tooth formation, demonstrating that the initiator tooth is necessary and sufficient for dental row formation, probably via FGF ligands released by 4 V1 to induce the formation of subsequent teeth. Our results show that by modifying the formation of the initiator tooth it is possible to control the formation of a dental row. This could help to explain the diversity of tooth patterns observed in actinopterygians and more broadly, how diverse traits evolved through molecular fine-tuning.
Effects of Arabidopsis wall associated kinase mutations on ESMERALDA1 and elicitor induced ROS
Date: 2021-05-01
Creator: Bruce D. Kohorn, Bridgid E. Greed, Gregory Mouille, Stéphane Verger, Susan L., Kohorn
Access: Open access
- Angiosperm cell adhesion is dependent on interactions between pectin polysaccharides which make up a significant portion of the plant cell wall. Cell adhesion in Arabidopsis may also be regulated through a pectin-related signaling cascade mediated by a putative O-fucosyltransferase ESMERALDA1 (ESMD1), and the Epidermal Growth Factor (EGF) domains of the pectin binding Wall associated Kinases (WAKs) are a primary candidate substrate for ESMD1 activity. Genetic interactions between WAKs and ESMD1 were examined using a dominant hyperactive allele of WAK2, WAK2cTAP, and a mutant of the putative O-fucosyltransferase ESMD1. WAK2cTAP expression results in a dwarf phenotype and activation of the stress response and reactive oxygen species (ROS) production, while esmd1 is a suppressor of a pectin deficiency induced loss of adhesion. Here we find that esmd1 suppresses the WAK2cTAP dwarf and stress response phenotype, including ROS accumulation and gene expression. Additional analysis suggests that mutations of the potential WAK EGF O-fucosylation site also abate the WAK2cTAP phenotype, yet only evidence for an N-linked but not O-linked sugar addition can be found. Moreover, a WAK locus deletion allele has no effect on the ability of esmd1 to suppress an adhesion deficiency, indicating WAKs and their modification are not a required component of the potential ESMD1 signaling mechanism involved in the control of cell adhesion. The WAK locus deletion does however affect the induction of ROS but not the transcriptional response induced by the elicitors Flagellin, Chitin and oligogalacturonides (OGs).
Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators
Date: 2016-01-01
Creator: E. S. Dickinson, A. S. Johnson, O. Ellers, P. S. Dickinson
Access: Open access
- Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of Homarus americanus. Although hearts in vivo are loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in H. americanus affect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart.
In situ HCR in non-traditional arthropods
Date: 2024-01-25
Creator: Heather Bruce, Hadley Wilson Horch
Access: Open access
- Visualizing the expression of genes is a fundamental tool in molecular biology. Traditional colorimetric in situ hybridization using long RNA probes has been a staple for visualizing gene expression but has many drawbacks. In situ HCR v3.0, developed by Choi et. al. 2018, offers improvements over traditional in situs in nearly every aspect: probes can simply be ordered rather than painstakingly cloned and transcribed, which also makes them cost-effective; an HCR takes just three days to complete rather than five or more days; HCR is robust and works well for first-time users; and HCR probes can be multiplexed, allowing four to eight genes to be visualized in a single sample. HCR has been used successfully in many arthropods, including insects (Drosophila, Tribolium), crustaceans (Parhyale, Daphnia, Artemia), and chelicerates (Limulus horseshoe crab, Acanthoscurria tarantula). In this demo, you will learn how to design and order HCR probes as well as best practices for experimental design.
Sensory-based niche partitioning in a multiple predator-multiple prey community
Date: 2015-05-20
Creator: Jay J. Falk, Hannah M. Ter Hofstede, Patricia L. Jones, Marjorie M. Dixon, Paul A., Faure, Elisabeth K.V. Kalko, Rachel A. Page
Access: Open access
- Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator-prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate- gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning.
TAKs, thylakoid membrane protein kinases associated with energy transduction
Date: 1999-04-02
Creator: Shaun Snyders, Bruce D. Kohorn
Access: Open access
- The phosphorylation of proteins within the eukaryotic photosynthetic membrane is thought to regulate a number of photosynthetic processes in land plants and algae. Both light quality and intensity influence protein kinase activity via the levels of reductants produced by the thylakoid electron transport chain. We have isolated a family of proteins called TAKs, Arabidopsis thylakoid membrane threonine kinases that phosphorylate the light harvesting complex proteins. TAK activity is enhanced by reductant and is associated with the photosynthetic reaction center II and the cytochrome b6f complex. TAKs are encoded by a gene family that has striking similarity to transforming growth factor β receptors of metazoans. Thus thylakoid protein phosphorylation may be regulated by a cascade of reductant-controlled membrane-bound protein kinases.