DNA Sequences Mediating the Transcriptional Response of theMix.2Homeobox Gene to Mesoderm Induction

AbstractPeptide growth factors can initiate changes in cell fate inXenopusectodermal explants and induce the formation of mesoderm. Marker genes expressed in mesoderm allow the analysis of whether, or how much, induction has occurred, but do not tell us what molecules are involved in carrying out the response. In this report we describe the isolation of genomic and cDNA clones ofMix.2, a gene closely related to theXenopushomeobox geneMix.1, and demonstrate that the promoter of theMix.2 gene is responsive to mesoderm induction signals when linked to a CAT reporter and microinjected into developingXenopusembryos. Like the chromosomalMix.1 gene, microinjectedMix.2 gene plasmids respond to activin in the presence of cycloheximide in animal cap assays and also respond to the embryonic inductive signal in Nieuwkoop recombinants. The injected promoter does not respond to TGF-β2 or FGF. Deletion analysis of theMix.2 promoter demonstrated that sequences required for maximal transcriptional activity in response to mesoderm induction are scattered across a 290-bp region. This is the first report of a microinjected plasmid responding to immediate-early transcriptional activation in developingXenopusembryos. This assay reduces the complexity of the cellular response to embryonic induction to the simple question of which molecules activate theMix.2 promoter and provides a sensitive and rapid test with which to pursue the answer

p53 as a regulator of cell differentiation

The present invention involves the role of p53 in the differentiation of embryonic tissues. More particularly, the present invention provides methods of the blocking of p53 function in embryonic tissues, and the use of these tissues as screening tools for substances that are capable of overcoming the p53-related block in differentation, both in vitro and in vivo. The similarities between undifferentiated embryonic cells and tumor cells is evident, and thus these assays serve as a model for possible cancer therapeutics. In addition, methods for identifying additional cellular components that interact p53 or p53-related pathways are provided.Board of Regents, University of Texas Syste

Ecological Complexity of Coral Recruitment Processes: Effects of Invertebrate Herbivores on Coral Recruitment and Growth Depends Upon Substratum Properties and Coral Species

Sarah W. Davies, Mikhail V. Matz, Integrative Biology Section, The University of Texas at Austin, Austin, Texas, United States of AmericaSarah W. Davies, Peter D. Vize, Department of Biological Sciences, University of Calgary, Calgary, Alberta, CanadaBackground: The transition from planktonic planula to sessile adult corals occurs at low frequencies and post settlement mortality is extremely high. Herbivores promote settlement by reducing algal competition. This study investigates whether invertebrate herbivory might be modulated by other ecological factors such as substrata variations and coral species identity. Methodology/Principal Findings: The experiment was conducted at the Flower Garden Banks, one of the few Atlantic reefs not experiencing considerable degradation. Tiles of differing texture and orientation were kept in bins surrounded by reef (24 m). Controls contained no herbivores while treatment bins contained urchins (Diadema antillarum) or herbivorous gastropods (Cerithium litteratum). Juvenile corals settling naturally were monitored by photography for 14 months to evaluate the effects of invertebrate herbivory and substratum properties. Herbivory reduced algae cover in urchin treatments. Two genera of brooding coral juveniles were observed, Agaricia and Porites, both of which are common but not dominant on adjacent reef. No broadcast spawning corals were observed on tiles. Overall, juveniles were more abundant in urchin treatments and on vertical, rough textured surfaces. Although more abundant, Agaricia juveniles were smaller in urchin treatments, presumably due to destructive overgrazing. Still, Agaricia growth increased with herbivory and substrata texture-orientation interactions were observed with reduced growth on rough tiles in control treatments and increased growth on vertical tiles in herbivore treatments. In contrast to Agaricia, Porites juveniles were larger on horizontal tiles, irrespective of herbivore treatment. Mortality was affected by substrata orientation with vertical surfaces increasing coral survival. Conclusions/Significance: We further substantiate that invertebrate herbivores play major roles in early settlement processes of corals and highlight the need for deeper understanding of ecological interactions modulating these effects. The absence of broadcast-spawning corals, even on a reef with consistently high coral cover, continues to expose the recruitment failure of these reef-building corals throughout the Caribbean.Natural Sciences and Engineering Research Council of Canada (NSERC) PGS-M to SWD; ACCESS Funding from the University of Calgary to SWD; National Science Foundation grant DEB-1054766 to MVM. Boat time provided by FGBNMS under permit# FGBNMS-2007-006. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biological Sciences, School ofIntegrative BiologyEmail: [email protected]

Fertilization in Broadcast-Spawning Corals of the Flower Garden Banks National Marine Sanctuary

Broadcast spawning is considered to be the dominant reproductive strategy for reef corals, but little is known about two critical postspawning processes, fertilization and early larval development. Instead, most efforts have focused on dispersal and recruitment. Since 1993, we have examined coral fertilization and development at the Flower Garden Banks, which contain two isolated reefs with predictable and dramatic annual mass spawning events in the northwestern Gulf of Mexico. Observations of in vitro fertilization indicate that the hermaphroditic scleractinian species Colpophyllia natans, Diploria strigosa, Monfastraea faveolata, and M. franksi all have high fertilization potentials when outcrossing. However, although D. strigosa can self-fertilize readily, self-fertilization levels within C. natans and the Montastraea species are low. In addition, interspecific crossing attempts among the hermaphroditic species of Montastraea (M. franksi, M. faveolata, and M. annularis) yielded low levels of fertilization. The differences observed in the timing of spawning and the low hybridization success between the Montastraea siblings lend additional support to their recent reclassification as separate species. Spawned egg samples collected immediately upon release from female colonies of the gonochoric species M. cavernosa and Stephanocoenia intersepta produced an unexpected observation—very high levels of fertilization. This suggests internal fertilization prior to egg release, a process that has not heretofore been observed in a broadcast-spawning scleractinian

An ontology for Xenopus anatomy and development

YesFunding provided by the Open Access Authors Fund

Model Systems for the Study of Kidney Development: Use of the Pronephros in the Analysis of Organ Induction and Patterning

AbstractMost vertebrate organs, once formed, continue to perform the function for which they were generated until the death of the organism. The kidney is a notable exception to this rule. Vertebrates, even those that do not undergo metamorphosis, utilize a progression of more complex kidneys as they grow and develop. This is presumably due to the changing conditions to which the organism must respond to retain what Homer Smith referred to as our physiological freedom. To quote, “Recognizing that we have the kind of blood we have because we have the kind of kidneys we have, we must acknowledge that our kidneys constitute the major foundation of our physiological freedom. Only because they work the way they do has it become possible for us to have bones, muscles, glands, and brains. Superficially, it might be said that the function of the kidneys is to make urine; but in a more considered view one can say that the kidneys make the stuff of philosophy itself” (“From Fish to Philosopher,” Little, Brown and Co., Boston, 1953). Different kidneys are used to make the stuff of philosophy at different stages of development depending on the age and needs of the organism, rather than the usual approach of simply making embryonic organs larger as the animal grows. Although evolution has provided the higher vertebrates with complex adult kidneys, they continue to utilize simple kidneys in embryogenesis. In lower vertebrates with simple adult kidneys, even more simple versions are used during early developmental stages. In this review the anatomy, development, and gene expression patterns of the embryonic kidney, the pronephros, will be described and compared to the more complex kidney forms. Despite some differences in anatomy, similar developmental pathways seem to be responsible for the induction and the response to induction in both evanescent and permanent kidney forms. Gene expression patterns can, therefore, be added to the morphological and functional data indicating that all forms of the kidney are closely related structures. Given the similarities between the development of simple and complex kidneys, the embryonic kidneys may be an ideal model system in which to investigate the genesis of multicomponent organ systems

Tight Temporal Consistency of Coral Mass Spawning at the Flower Garden Banks, Gulf of Mexico, from 1997-2003

Mass spawning by the hard corals of the Flower Garden Banks National Marine Sanctuary has been studied for over a decade. In this report we present observations by a single set of experienced observers on spawning events extending over seven years, on spawning activity, lack of activity and coordination within and between species. This compilation shows that the spawning times of each species are extremely consistent during major events, with onset and hiatus often predictable to within seven minutes, and in some species to within two minutes. In addition to the extraordinary degree of temporal regulation, the other striking feature of the spawning schedule is the uniqueness of most spawning windows. With the exception of Diploria strigosa, each of the major spawning species—Colpophyllia natans, Montrastraea cavernosa, M. annularis, M. faveolata, M. franksi and Stephanocoenia intersepta—has a unique window of time in which it and no other coral species releases gametes. Spawning times for the 2005-2008 seasons are predicted based on these findings

Separate Introns Gained within Short and Long Soluble Peridinin-Chlorophyll a-Protein Genes during Radiation of Symbiodinium (Dinophyceae) Clade A and B Lineages

Correction: 21 Jan 2015: The PLOS ONE Staff (2015) Correction: Separate Introns Gained within Short and Long Soluble Peridinin-Chlorophyll a-Protein Genes during Radiation of Symbiodinium (Dinophyceae) Clade A and B Lineages. PLOS ONE 10(1): e0117735. https://doi.org/10.1371/journal.pone.0117735Here we document introns in two Symbiodinium clades that were most likely gained following divergence of this genus from other peridinin-containing dinoflagellate lineages. Soluble peridinin-chlorophyll a-proteins (sPCP) occur in short and long forms in different species. Duplication and fusion of short sPCP genes produced long sPCP genes. All short and long sPCP genes characterized to date, including those from free living species and Symbiodinium sp. 203 (clade C/type C2) are intronless. However, we observed that long sPCP genes from two Caribbean Symbiodinium clade B isolates each contained two introns. To test the hypothesis that introns were gained during radiation of clade B, we compared sPCP genomic and cDNA sequences from 13 additional distinct Caribbean and Pacific Symbiodinium clade A, B, and F isolates. Long sPCP genes from all clade B/B1 and B/B19 descendants contain orthologs of both introns. Short sPCP genes from S. pilosum (A/A2) and S. muscatinei (B/B4) plus long sPCP genes from S. microadriaticum (A/A1) and S. kawagutii (F/F1) are intronless. Short sPCP genes of S. microadriaticum have a third unique intron. Symbiodinium clade B long sPCP sequences are useful for assessing divergence among B1 and B19 descendants. Phylogenetic analyses of coding sequences from four dinoflagellate orders indicate that introns were gained independently during radiation of Symbiodinium clades A and B. Long sPCP introns were present in the most recent common ancestor of Symbiodinium clade B core types B1 and B19, which apparently diverged sometime during the Miocene. The clade A short sPCP intron was either gained by S. microadriaticum or possibly by the ancestor of Symbiodinium types A/A1, A3, A4 and A5. The timing of short sPCP intron gain in Symbiodinium clade A is less certain. But, all sPCP introns were gained after fusion of ancestral short sPCP genes, which we confirm as occurring once in dinoflagellate evolution

Developmental Basis of Pronephric Defects in Xenopus Body Plan Phenotypes

AbstractWe have used monoclonal antibodies that recognize the pronephric tubules or pronephric duct to explore the induction of the embryonic kidney in developing Xenopus embryos. Morphogenesis of the pronephros was examined in UV-ventralized and lithium-dorsalized embryos. We find that the pronephric tubules are present in all but the strongest UV-induced phenotypes, but absent from relatively moderate lithium phenotypes. Interestingly the pronephric duct, which develops from the ventroposterior portion of the pronephric anlage, is missing from more of the mild UV phenotypes than are pronephric tubules. The loss of the capacity to form pronephroi in UV-ventralized embryos is caused by the loss of tissues capable of inducing the pronephric mesoderm, as marginal zone explants from ventralized embryos are still competent to respond to pronephric-inductive signals. Explant recombination experiments indicate that the tissue responsible for both the loss of pronephroi in UV-ventralized embryos and the induction of pronephroi during normal development is the anterior somites. The absence of pronephroi in relatively mild lithium phenotypes has a developmental basis different from that of the UV phenotype, as explants from lithium-treated embryos are effective inducers of pronephroi in recombinants with competent mesoderm, even though they themselves do not form pronephroi in isolation. Together these data indicate that dorsal tissues, especially the anterior somites, are responsible for the establishment of the intermediate mesoderm and the induction of the embryonic kidneys and that even mild dorsalization destroys the capacity to form cells competent to receive this signal