Research and Publications - Department of Biological Sciences

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Ubiquitin conjugating enzymes participate in polyglutamine protein aggregation
(BMC, 2007) Howard, Rebecca A.; Sharma, Pratima; Hajjar, Connie; Caldwell, Kim A.; Caldwell, Guy A.; Du Breuil, Rusla; Moore, Rhonda; Boyd, Lynn; University of Alabama Huntsville; University of Alabama Tuscaloosa
Background: Protein aggregation is a hallmark of several neurodegenerative diseases including Huntington's disease and Parkinson's disease. Proteins containing long, homopolymeric stretches of glutamine are especially prone to form aggregates. It has long been known that the small protein modifier, ubiquitin, localizes to these aggregates. In this report, nematode and cell culture models for polyglutamine aggregation are used to investigate the role of the ubiquitin pathway in protein aggregation. Results: Ubiquitin conjugating enzymes (Ubc's) were identified that affect polyglutamine aggregates in C. elegans. Specifically, RNAi knockdown of ubc-2 or ubc-22 causes a significant increase in the size of aggregates as well as a reduction in aggregate number. In contrast, RNAi of ubc-1, ubc-13, or uev-1 leads to a reduction of aggregate size and eliminates ubiquitin and proteasome localization to aggregates. In cultured human cells, shRNA knockdown of human homologs of these Ubc's (Ube2A, UbcH5b, and E2- 25K) causes similar effects indicating a conserved role for ubiquitination in polyglutamine protein aggregation. Conclusion: Results of knockdown of different Ubc enzymes indicate that at least two different and opposing ubiquitination events occur during polyglutamine aggregation. The loss of ubiquitin localization after ubc-1, ubc-13, or uev-1 knockdown suggests that these enzymes might be directly involved in ubiquitination of aggregating proteins.
Drosophila Pupal Abdomen Immunohistochemistry
(MyJove Corporation, 2011) Wang, Wei; Yoder, John H.; University of Alabama Tuscaloosa
The Drosophila pupal abdomen is an established model system for the study of epithelial morphogenesis and the development of sexually dimorphic morphologies(1-3). During pupation, which spans approximately 96 hours (at 25 degrees C), proliferating populations of imaginal cells replace the larval epidermis to generate the adult abdominal segments. These imaginal cells, born during embryogenesis, exist as lateral pairs of histoblast nests in each abdominal segment of the larvae. Four pairs of histoblast nests give rise to the adult dorsal cuticle (anterior and posterior dorsal nests), the ventral cuticle (ventral nests) and the spiracles associated with each segment (spiracle nests)(4). Upon puparation, these diploid cells (distinguishable by size from the larger polyploid larval epidermal cells-LECs) begin a stereotypical process of proliferation, migration and replacement of the LECs. Various molecular and genetic tools can be employed to investigate the contributions of genetic pathways involved in morphogenesis of the adult abdomen. Ultimate adult phenotypes are typically analyzed following dissection of adult abdominal cuticles. However, investigation of the underlying molecular processes requires immunohistochemical analyses of the pupal epithelium, which present unique challenges. Temporally dynamic morphogenesis and the interactions of two distinct epithelial populations (larval and imaginal) generate a fragile tissue prone to excessive cell loss during dissection and subsequent processing. We have developed methods of dissection, fixation, mounting and imaging of the Drosophila pupal abdominem epithelium for immunohistochemical studies that generate consistent high quality samples suitable for confocal or standard fluorescent microscopy.
dtorsin, the Drosophila Ortholog of the Early-Onset Dystonia TOR1A (DYT1), Plays a Novel Role in Dopamine Metabolism
(PLOS, 2011) Wakabayashi-Ito, Noriko; Doherty, Olugbenga M.; Moriyama, Hideaki; Breakefield, Xandra O.; Gusella, James F.; O'Donnell, Janis M.; Ito, Naoto; Harvard University; Massachusetts General Hospital; University of Alabama Tuscaloosa; University of Nebraska Lincoln; Harvard Medical School
Dystonia represents the third most common movement disorder in humans. At least 15 genetic loci (DYT1-15) have been identified and some of these genes have been cloned. TOR1A (formally DYT1), the gene responsible for the most common primary hereditary dystonia, encodes torsinA, an AAA ATPase family protein. However, the function of torsinA has yet to be fully understood. Here, we have generated and characterized a complete loss-of-function mutant for dtorsin, the only Drosophila ortholog of TOR1A. Null mutation of the X-linked dtorsin was semi-lethal with most male flies dying by the pre-pupal stage and the few surviving adults being sterile and slow moving, with reduced cuticle pigmentation and thin, short bristles. Third instar male larvae exhibited locomotion defects that were rescued by feeding dopamine. Moreover, biochemical analysis revealed that the brains of third instar larvae and adults heterozygous for the loss-of-function dtorsin mutation had significantly reduced dopamine levels. The dtorsin mutant showed a very strong genetic interaction with Pu (Punch: GTP cyclohydrolase), the ortholog of the human gene underlying DYT14 dystonia. Biochemical analyses revealed a severe reduction of GTP cyclohydrolase protein and activity, suggesting that dtorsin plays a novel role in dopamine metabolism as a positive-regulator of GTP cyclohydrolase protein. This dtorsin mutant line will be valuable for understanding this relationship and potentially other novel torsin functions that could play a role in human dystonia.
Fatty Acids Identified in the Burmese Python Promote Beneficial Cardiac Growth
(American Association for the Advancement of Science, 2011) Riquelme, Cecilia A.; Magida, Jason A.; Harrison, Brooke C.; Wall, Christopher E.; Marr, Thomas G.; Secor, Stephen M.; Leinwand, Leslie A.; University of Colorado Boulder; University of Alabama Tuscaloosa
Burmese pythons display a marked increase in heart mass after a large meal. We investigated the molecular mechanisms of this physiological heart growth with the goal of applying this knowledge to the mammalian heart. We found that heart growth in pythons is characterized by myocyte hypertrophy in the absence of cell proliferation and by activation of physiological signal transduction pathways. Despite high levels of circulating lipids, the postprandial python heart does not accumulate triglycerides or fatty acids. Instead, there is robust activation of pathways of fatty acid transport and oxidation combined with increased expression and activity of superoxide dismutase, a cardioprotective enzyme. We also identified a combination of fatty acids in python plasma that promotes physiological heart growth when injected into either pythons or mice.
Functional Links Between A beta Toxicity, Endocytic Trafficking, and Alzheimer's Disease Risk Factors in Yeast
(American Association for the Advancement of Science, 2011) Treusch, Sebastian; Hamamichi, Shusei; Goodman, Jessica L.; Matlack, Kent E. S.; Chung, Chee Yeun; Baru, Valeriya; Shulman, Joshua M.; Parrado, Antonio; Bevis, Brooke J.; Valastyan, Julie S.; Han, Haesun; Lindhagen-Persson, Malin; Reiman, Eric M.; Evans, Denis A.; Bennett, David A.; Olofsson, Anders; DeJager, Philip L.; Tanzi, Rudolph E.; Caldwell, Kim A.; Caldwell, Guy A.; Lindquist, Susan; Massachusetts Institute of Technology (MIT); Whitehead Institute; Howard Hughes Medical Institute; University of Alabama Tuscaloosa; Harvard University; Brigham & Women's Hospital; Harvard Medical School; Broad Institute; Massachusetts General Hospital; Umea University; Translational Genomics Research Institute; University of Arizona; Banner Research; Banner Health; Banner Alzheimer's Institute; Rush University
A beta (beta-amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled A beta toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to A beta was previously unknown. The factors identified in yeast modified A beta toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, A beta impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between A beta, endocytosis, and human AD risk factors can be ascertained with yeast as a model system.
Phylogenetic Diversity, Host-Specificity and Community Profiling of Sponge-Associated Bacteria in the Northern Gulf of Mexico
(PLOS, 2011) Erwin, Patrick M.; Olson, Julie B.; Thacker, Robert W.; University of Alabama Birmingham; University of Alabama Tuscaloosa
Background: Marine sponges can associate with abundant and diverse consortia of microbial symbionts. However, associated bacteria remain unexamined for the majority of host sponges and few studies use phylogenetic metrics to quantify symbiont community diversity. DNA fingerprinting techniques, such as terminal restriction fragment length polymorphisms (T-RFLP), might provide rapid profiling of these communities, but have not been explicitly compared to traditional methods. Methodology/Principal Findings: We investigated the bacterial communities associated with the marine sponges Hymeniacidon heliophila and Haliclona tubifera, a sympatric tunicate, Didemnum sp., and ambient seawater from the northern Gulf of Mexico by combining replicated clone libraries with T-RFLP analyses of 16S rRNA gene sequences. Clone libraries revealed that bacterial communities associated with the two sponges exhibited lower species richness and lower species diversity than seawater and tunicate assemblages, with differences in species composition among all four source groups. T-RFLP profiles clustered microbial communities by source; individual T-RFs were matched to the majority (80.6%) of clone library sequences, indicating that T-RFLP analysis can be used to rapidly profile these communities. Phylogenetic metrics of community diversity indicated that the two sponge-associated bacterial communities include dominant and host-specific bacterial lineages that are distinct from bacteria recovered from seawater, tunicates, and unrelated sponge hosts. In addition, a large proportion of the symbionts associated with H. heliophila were shared with distant, conspecific host populations in the southwestern Atlantic (Brazil). Conclusions/Significance: The low diversity and species-specific nature of bacterial communities associated with H. heliophila and H. tubifera represent a distinctly different pattern from other, reportedly universal, sponge-associated bacterial communities. Our replicated sampling strategy, which included samples that reflect the ambient environment, allowed us to differentiate resident symbionts from potentially transient or prey bacteria. Pairing replicated clone library construction with rapid community profiling via T-RFLP analyses will greatly facilitate future studies of sponge-microbe symbioses.
A multigene phylogeny of Olpidium and its implications for early fungal evolution
(BMC, 2011) Sekimoto, Satoshi; Rochon, D'Ann; Long, Jennifer E.; Dee, Jaclyn M.; Berbee, Mary L.; University of British Columbia; Agriculture & Agri Food Canada; University of Alabama Tuscaloosa; University of Victoria
Background: From a common ancestor with animals, the earliest fungi inherited flagellated zoospores for dispersal in water. Terrestrial fungi lost all flagellated stages and reproduce instead with nonmotile spores. Olpidium virulentus (= Olpidium brassicae), a unicellular fungus parasitizing vascular plant root cells, seemed anomalous. Although Olpidium produces zoospores, in previous phylogenetic studies it appeared nested among the terrestrial fungi. Its position was based mainly on ribosomal gene sequences and was not strongly supported. Our goal in this study was to use amino acid sequences from four genes to reconstruct the branching order of the early-diverging fungi with particular emphasis on the position of Olpidium. Results: We concatenated sequences from the Ef-2, RPB1, RPB2 and actin loci for maximum likelihood and Bayesian analyses. In the resulting trees, Olpidium virulentus, O. bornovanus and non-flagellated terrestrial fungi formed a strongly supported clade. Topology tests rejected monophyly of the Olpidium species with any other clades of flagellated fungi. Placing Olpidium at the base of terrestrial fungi was also rejected. Within the terrestrial fungi, Olpidium formed a monophyletic group with the taxa traditionally classified in the phylum Zygomycota. Within Zygomycota, Mucoromycotina was robustly monophyletic. Although without bootstrap support, Monoblepharidomycetes, a small class of zoosporic fungi, diverged from the basal node in Fungi. The zoosporic phylum Blastocladiomycota appeared as the sister group to the terrestrial fungi plus Olpidium. Conclusions: This study provides strong support for Olpidium as the closest living flagellated relative of the terrestrial fungi. Appearing nested among hyphal fungi, Olpidium's unicellular thallus may have been derived from ancestral hyphae. Early in their evolution, terrestrial hyphal fungi may have reproduced with zoospores.
Synthesizing and databasing fossil calibrations: divergence dating and beyond
(Royal Society of London, 2011) Ksepka, Daniel T.; Benton, Michael J.; Carrano, Matthew T.; Gandolfo, Maria A.; Head, Jason J.; Hermsen, Elizabeth J.; Joyce, Walter G.; Lamm, Kristin S.; Patane, Jose S. L.; Phillips, Matthew J.; Polly, P. David; Van Tuinen, Marcel; Ware, Jessica L.; Warnock, Rachel C. M.; Parham, James F.; North Carolina State University; University of Bristol; Smithsonian Institution; Smithsonian National Museum of Natural History; Cornell University; University of Toronto; University Toronto Mississauga; Eberhard Karls University of Tubingen; Instituto Butantan; University of Queensland; Indiana University Bloomington; University of North Carolina; University of North Carolina Wilmington; Rutgers State University Newark; Rutgers State University New Brunswick; American Museum of Natural History (AMNH); University of Alabama Tuscaloosa
Divergence dating studies, which combine temporal data from the fossil record with branch length data from molecular phylogenetic trees, represent a rapidly expanding approach to understanding the history of life. National Evolutionary Synthesis Center hosted the first Fossil Calibrations Working Group (3-6 March, 2011, Durham, NC, USA), bringing together palaeontologists, molecular evolutionists and bioinformatics experts to present perspectives from disciplines that generate, model and use fossil calibration data. Presentations and discussions focused on channels for interdisciplinary collaboration, best practices for justifying, reporting and using fossil calibrations and roadblocks to synthesis of palaeontological and molecular data. Bioinformatics solutions were proposed, with the primary objective being a new database for vetted fossil calibrations with linkages to existing resources, targeted for a 2012 launch.
Sympathetic nerve activity and whole body heat stress in humans
(American Psyiological Society, 2011) Low, David A.; Keller, David M.; Wingo, Jonathan E.; Brothers, R. Matthew; Crandall, Craig G.; University of Texas Southwestern Medical Center Dallas; University of Texas Arlington; University of Alabama Tuscaloosa; University of Texas Austin
Low DA, Keller DM, Wingo JE, Brothers RM, Crandall CG. Sympathetic nerve activity and whole body heat stress in humans. J Appl Physiol 111: 1329-1334, 2011. First published August 25, 2011; doi:10.1152/japplphysiol.00498.2011.-We and others have shown that moderate passive whole body heating (i.e., increased internal temperature similar to 0.7 degrees C) increases muscle (MSNA) and skin sympathetic nerve activity (SSNA). It is unknown, however, if MSNA and/or SSNA continue to increase with more severe passive whole body heating or whether these responses plateau following moderate heating. The aim of this investigation was to test the hypothesis that MSNA and SSNA continue to increase from a moderate to a more severe heat stress. Thirteen subjects, dressed in a water-perfused suit, underwent at least one passive heat stress that increased internal temperature similar to 1.3 degrees C, while either MSNA (n = 8) or SSNA (n = 8) was continuously recorded. Heat stress significantly increased mean skin temperature (Delta similar to 5 degrees C, P < 0.001), internal temperature (Delta similar to 1.3 degrees C, P < 0.001), mean body temperature (Delta similar to 2.0 C, P < 0.001), heart rate (Delta similar to 40 beats/min, P < 0.001), and cutaneous vascular conductance [Delta similar to 1.1 arbitrary units (AU)/mmHg, P < 0.001]. Mean arterial blood pressure was well maintained (P = 0.52). Relative to baseline, MSNA increased midway through heat stress (Delta core temperature 0.63 +/- 0.01 degrees C) when expressed as burst frequency (26 +/- 14 to 45 +/- 16 bursts/min, P = 0.001), burst incidence (39 +/- 13 to 48 +/- 14 bursts/100 cardiac cyles, P = 0.03), or total activity (317 +/- 170 to 489 +/- 150 units/min, P = 0.02) and continued to increase until the end of heat stress (burst frequency: 61 +/- 15 bursts/min, P = 0.01; burst incidence: 56 +/- 11 bursts/100 cardiac cyles, P = 0.04; total activity: 648 +/- 158 units/min, P = 0.01) relative to the mid-heating stage. Similarly, SSNA (total activity) increased midway through the heat stress (normothermia; 1,486 +/- 472 to mid heat stress 6,467 +/- 5,256 units/min, P = 0.03) and continued to increase until the end of heat stress (11,217 +/- 6,684 units/min, P = 0.002 vs. mid-heat stress). These results indicate that both MSNA and SSNA continue to increase as internal temperature is elevated above previously reported values.
Modeling Relationships among 217 Fires Using Remote Sensing of Burn Severity in Southern Pine Forests
(MDPI, 2011-09-07) Malone, Sparkle L.; Kobziar, Leda N.; Staudhammer, Christina L.; Abd-Elrahman, Amr; State University System of Florida; University of Florida; University of Alabama Tuscaloosa
Pine flatwoods forests in the southeastern US have experienced severe wildfires over the past few decades, often attributed to fuel load build-up. These forest communities are fire dependent and require regular burning for ecosystem maintenance and health. Although prescribed fire has been used to reduce wildfire risk and maintain ecosystem integrity, managers are still working to reintroduce fire to long unburned areas. Common perception holds that reintroduction of fire in long unburned forests will produce severe fire effects, resulting in a reluctance to prescribe fire without first using expensive mechanical fuels reduction techniques. To inform prioritization and timing of future fire use, we apply remote sensing analysis to examine the set of conditions most likely to result in high burn severity effects, in relation to vegetation, years since the previous fire, and historical fire frequency. We analyze Landsat imagery-based differenced Normalized Burn Ratios (dNBR) to model the relationships between previous and future burn severity to better predict areas of potential high severity. Our results show that remote sensing techniques are useful for modeling the relationship between elevated risk of high burn severity and the amount of time between fires, the type of fire (wildfire or prescribed burn), and the historical frequency of fires in pine flatwoods forests.
Towards an empirical relationship between root length density and root number in windbreak-grown cadaghi (Corymbia torelliana) trees
(2011-11-30) Tamang, Bijay; Andreu, Michael G.; Staudhammer, Christina L.; Rockwood, Donald L.; Jose, Shibu; University of Alabama Tuscaloosa
Because windbreaks are planted for sustainable agriculture but may lower crop yields near them due to competition, suitable competition mitigation methods must be applied at the windbreak-crop interface to increase crop yields. Effective underground competition management requires information on important root variables such as preferential root growth direction and root length density (RLD, root length per unit volume of soil). This study examined root isotropy (i.e., uniformity in all directions) in windbreak- grown cadaghi (Corymbia torelliana) trees in south Florida and developed an empirical relationship between RLD and number of roots (N) per unit of surface of soil exiting the trench face. Numbers of roots exiting the frontal face parallel to the windbreak (NX), vertical face perpendicular to the frontal face (NY), and basal horizontal face (NZ) of 10 x 10 x 10 cm soil cubes were counted. Cadaghi roots were anisotropic and had horizontal growth preference. Average root numbers were ranked NX>NY>NZ. Both NX and the average root number exiting X, Y and Z faces of the soil cube (NAVG) were significant variables for estimating RLD. The coefficients of NX and NAVG were 1.1 and 3.1. These results should be helpful to manage underground competition effectively at the windbreak-crop interface to improve crop yields.
Deletion of U(L)21 Causes a Delay in the Early Stages of the Herpes Simplex Virus 1 Replication Cycle
(American Society of Microbiology, 2012) Mbong, Ekaette F.; Woodley, Lucille; Frost, Elizabeth; Baines, Joel D.; Duffy, Carol; University of Alabama Tuscaloosa; Cornell University
The herpes simplex virus 1 (HSV-1) U(L)21 gene encodes a 62-kDa tegument protein with homologs in the alpha-, beta-, and gammaherpesvirus subfamilies. In the present study, we characterized a novel U(L)21-null virus and its genetic repair to determine whether this protein plays a role in early stages of the HSV-1 replication cycle. Single-step growth analyses, protein synthesis time courses, and mRNA quantifications indicated that the absence of U(L)21 results in a delay early in the HSV-1 replication cycle.
Complete Genome Sequence of Rahnella aquatilis CIP 78.65
(American Society of Microbiology, 2012) Martinez, Robert J.; Bruce, David; Detter, Chris; Goodwin, Lynne A.; Han, James; Han, Cliff S.; Held, Brittany; Land, Miriam L.; Mikhailova, Natalia; Nolan, Matt; Pennacchio, Len; Pitluck, Sam; Tapia, Roxanne; Woyke, Tanja; Sobeckya, Patricia A.; University of Alabama Tuscaloosa; United States Department of Energy (DOE); Los Alamos National Laboratory; Joint BioEnergy Institute - JBEI; Joint Genome Institute - JGI; Oak Ridge National Laboratory
Rahnella aquatilis CIP 78.65 is a gammaproteobacterium isolated from a drinking water source in Lille, France. Here we report the complete genome sequence of Rahnella aquatilis CIP 78.65, the type strain of R. aquatilis.
Maple syrup urine disease: new insights from a zebrafish model
(Company of Biologists, 2012) Roberts, Nathan B.; University of Alabama Tuscaloosa
Deletion of the Herpes Simplex Virus 1 U(L)49 Gene Results in mRNA and Protein Translation Defects That Are Complemented by Secondary Mutations in U(L)41
(American Society of Microbiology, 2012) Mbong, Ekaette F.; Woodley, Lucille; Dunkerley, Eric; Schrimpf, Jane E.; Morrison, Lynda A.; Duffy, Carol; University of Alabama Tuscaloosa; Saint Louis University
Herpes simplex virus 1 (HSV-1) virions, like those of all herpesviruses, contain a protein layer termed the tegument localized between the capsid and the envelope. VP22, encoded by the U(L)49 gene, is one of the most abundant tegument proteins in HSV-1 virions. Studies with a U(L)49-null mutant showed that the absence of VP22 resulted in decreased protein synthesis at late times in infection. VP22 is known to form a tripartite complex with VP16 and vhs through direct interactions with VP16. Given that U(L)49-null mutants have been shown to acquire spontaneous secondary mutations in the U(L)41 gene, which encodes vhs, we hypothesized that VP22 and vhs may play antagonistic roles during HSV-1 infections. In the present study, we show that the protein synthesis defect observed in U(L)49-null virus infections was rescued by a secondary, compensatory frameshift mutation in U(L)41. A double mutant bearing a deletion of U(L)49 and a point mutation in vhs previously shown to specifically abrogate vhs's RNase activity also resulted in a rescue of protein synthesis. To determine whether the U(L)49(-) protein synthesis defect, and the rescue by secondary mutations in vhs, occurred at the mRNA and/or translational levels, quantitative reverse transcriptase PCR (qRT-PCR) and polysome analyses were performed. We found that the absence of VP22 caused a small decrease in mRNA levels as well as a defect in polysome assembly that was independent of mRNA abundance. Both defects were complemented by the secondary mutations in vhs, indicating functional interplay between VP22 and vhs in both accumulation and translation of viral mRNAs.
Best Practices for Justifying Fossil Calibrations
(Oxford University Press, 2012) Parham, James F.; Donoghue, Philip C. J.; Bell, Christopher J.; Calway, Tyler D.; Head, Jason J.; Holroyd, Patricia A.; Inoue, Jun G.; Irmis, Randall B.; Joyce, Walter G.; Ksepka, Daniel T.; Patane, Jose S. L.; Smith, Nathan D.; Tarver, James E.; van Tuinen, Marcel; Yang, Ziheng; Angielczyk, Kenneth D.; Greenwood, Jenny M.; Hipsley, Christy A.; Jacobs, Louis; Makovicky, Peter J.; Mueller, Johannes; Smith, Krister T.; Theodor, Jessica M.; Warnock, Rachel C. M.; Benton, Michael J.; University of Alabama Tuscaloosa; Field Museum of Natural History (Chicago); University of Bristol; University of Texas Austin; University of Chicago; University of Nebraska Lincoln; University of California Berkeley; University of Tokyo; University of Utah; Eberhard Karls University of Tubingen; North Carolina State University; Instituto Butantan; Dartmouth College; University of North Carolina; University of North Carolina Wilmington; University of London; University College London; Leibniz Institut fur Evolutions und Biodiversitatsforschung; Humboldt University of Berlin; University of California Santa Cruz; Southern Methodist University; Senckenberg Gesellschaft fur Naturforschung (SGN); University of Calgary
Microevolutionary Distribution of Isogenicity in a Self-fertilizing Fish (Kryptolebias marmoratus) in the Florida Keys
(Oxford University Press, 2012) Tatarenkov, Andrey; Earley, Ryan L.; Taylor, D. Scott; Avise, John C.; University of California Irvine; University of Alabama Tuscaloosa
The mangrove rivulus Kryptolebias marmoratus and a closely related species are the world's only vertebrates that routinely self-fertilize. Such uniqueness presents a model for understanding why this reproductive mode, common in plants and invertebrates, is so rare in vertebrates. A survey of 32 highly polymorphic loci in > 200 specimens of mangrove rivulus from multiple locales in the Florida Keys, USA, revealed extensive population-genetic structure on microspatial and micro-temporal scales. Observed heterozygosities were severely constrained, as expected for a hermaphroditic species with a mixed-mating system and low rates of outcrossing. Despite the pronounced population structure and the implied restrictions on effective gene flow, isogenicity (genetic identity across individuals) within and among local inbred populations was surprisingly low even after factoring out probable de novo mutations. Results indicate that neither frequent bottlenecks nor directional genetic adaptation to local environmental conditions were the primary driving forces impacting multilocus population-genetic architecture in this self-fertilizing vertebrate species. On the other hand, a high diversity of isogenic lineages within relatively small and isolated local populations is consistent with the action of diversifying selection driven by the extreme spatio-temporal environmental variability that is characteristic of mangrove habitats.
Effects of short-term exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on microRNA expression in zebrafish embryos
(Elsevier, 2012) Jenny, Matthew J.; Aluru, Neelakanteswar; Hahn, Mark E.; Woods Hole Oceanographic Institution; University of Alabama Tuscaloosa
Although many drugs and environmental chemicals are teratogenic, the mechanisms by which most toxicants disrupt embryonic development are not well understood. MicroRNAs, single-stranded RNA molecules of similar to 22 nt that regulate protein expression by inhibiting mRNA translation and promoting mRNA sequestration or degradation, are important regulators of a variety of cellular processes including embryonic development and cellular differentiation. Recent studies have demonstrated that exposure to xenobiotics can alter microRNA expression and contribute to the mechanisms by which environmental chemicals disrupt embryonic development. In this study we tested the hypothesis that developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a well-known teratogen, alters microRNA expression during zebrafish development. We exposed zebrafish embryos to DMSO (0.1%) or TCDD (5 nM) for 1 h at 30 hours post fertilization (hpf) and measured microRNA expression using several methods at 36 and 60 hpf. TCDD caused strong induction of CYP1A at 36 hpf (62-fold) and 60 hpf (135-fold) as determined by real-time RT-PCR, verifying the effectiveness of the exposure. MicroRNA expression profiles were determined using microarrays (Agilent and Exicion), next-generation sequencing (SOLiD), and real-time RT-PCR. The two microarray platforms yielded results that were similar but not identical; both showed significant changes in expression of miR-451, 23a, 23b, 24 and 27e at 60 hpf. Multiple analyses were performed on the SOLiD sequences yielding a total of 16 microRNAs as differentially expressed by TCDD in zebrafish embryos. However, miR-27e was the only microRNA to be identified as differentially expressed by all three methods (both microarrays, SOLiD sequencing, and real-time RT-PCR). These results suggest that TCDD exposure causes modest changes in expression of microRNAs, including some (miR-451, 23a, 23b, 24 and 27e) that are critical for hematopoiesis and cardiovascular development. (C) 2012 Elsevier Inc. All rights reserved.
Aggression and Related Behavioral Traits: The Impact of Winning and Losing and the Role of Hormones
(Oxford University Press, 2012) Chang, Ching; Li, Cheng-Yu; Earley, Ryan L.; Hsu, Yuying; National Taiwan Normal University; University of Alabama Tuscaloosa
A suite of correlated behaviors reflecting between-individual consistency in behavior across multiple situations is termed a "behavioral syndrome." Researchers have suggested that a cause for the correlation between different behaviors might lie in the neuroendocrine system. In this study, we examined the relationships between aggressiveness (a fish's readiness to perform gill display to its mirror image) and each of boldness (the readiness to emerge from a shelter), exploratory tendency (the readiness to approach a novel shelter), and learning performance (the probability of entering the correct reservoir in a T-maze test) in a mangrove rivulus, Kryptolebias marmoratus. We explored the possibility that the relationships between them arise because these behaviors are all modulated by cortisol and testosterone. We also tested the stability of the relationships between these behaviors shortly after using a winning or losing experience to alter individuals' aggressiveness. The results were that aggressiveness correlated positively with boldness and the tendency to explore, and that these three behavioral traits were all positively correlated with pre-experience testosterone levels. Aggressiveness and boldness also positively correlated with pre-experience cortisol levels; exploratory tendency did not. The relationship between aggressiveness and boldness appeared to be stronger than that between either of them and exploratory tendency. These results suggest that testosterone and cortisol play important roles in mediating the correlations between these behavioral traits. Learning performance was not significantly correlated with the other behavioral traits or with levels of testosterone or cortisol. Recent experience in contests influenced individuals' aggressiveness, tendency to explore, and learning performance but not their boldness; individuals that received a winning experience were quicker to display to their mirror image and performed better in the learning task but were slower to approach a novel object than were individuals that lost. Contest experience did not, however, significantly influence the relationships between aggressiveness and any of boldness, exploratory tendency, or learning performance. The results show that the individual components of a suite of correlated behaviors can preserve a flexibility to respond differently to environmental stimuli.
Rediscovery of Leptoxis compacta (Anthony, 1854) (Gastropoda: Cerithioidea: Pleuroceridae)
(PLOS, 2012) Whelan, Nathan V.; Johnson, Paul D.; Harris, Phil M.; University of Alabama Tuscaloosa
The Mobile River Basin is a hotspot of molluscan endemism, but anthropogenic activities have caused at least 47 molluscan extinctions, 37 of which were gastropods, in the last century. Nine of these suspected extinctions were in the freshwater gastropod genus Leptoxis (Cerithioidea: Pleuroceridae). Leptoxis compacta, a Cahaba River endemic, has not been collected for > 70 years and was formally declared extinct in 2000. Such gastropod extinctions underscore the imperilment of freshwater resources and the current biodiversity crisis in the Mobile River Basin. During a May 2011 gastropod survey of the Cahaba River in central Alabama, USA, L. compacta was rediscovered. The identification of snails collected was confirmed through conchological comparisons to the L. compacta lectotype, museum records, and radulae morphology of historically collected L. compacta. Through observations of L. compacta in captivity, we document for the first time that the species lays eggs in short, single lines. Leptoxis compacta is restricted to a single location in the Cahaba River, and is highly susceptible to a single catastrophic extinction event. As such, the species deserves immediate conservation attention. Artificial propagation and reintroduction of L. compacta into its native range may be a viable recovery strategy to prevent extinction from a single perturbation event.

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