Chromosomal organization of adrenergic receptor genes.

The adrenergic receptors (ARs) (subtypes alpha 1, alpha 2, beta 1, and beta 2) are a prototypic family of guanine nucleotide binding regulatory protein-coupled receptors that mediate the physiological effects of the hormone epinephrine and the neurotransmitter norepinephrine. We have previously assigned the genes for beta 2- and alpha 2-AR to human chromosomes 5 and 10, respectively. By Southern analysis of somatic cell hybrids and in situ chromosomal hybridization, we have now mapped the alpha 1-AR gene to chromosome 5q32----q34, the same position as beta 2-AR, and the beta 1-AR gene to chromosome 10q24----q26, the region where alpha 2-AR is located. In mouse, both alpha 2- and beta 1-AR genes were assigned to chromosome 19, and the alpha 1-AR locus was localized to chromosome 11. Pulsed field gel electrophoresis has shown that the alpha 1- and beta 2-AR genes in humans are within 300 kilobases (kb) and the distance between the alpha 2- and beta 1-AR genes is less than 225 kb. The proximity of these two pairs of AR genes and the sequence similarity that exists among all the ARs strongly suggest that they are evolutionarily related. Moreover, they likely arose from a common ancestral receptor gene and subsequently diverged through gene duplication and chromosomal duplication to perform their distinctive roles in mediating the physiological effects of catecholamines. The AR genes thus provide a paradigm for understanding the evolution of such structurally conserved yet functionally divergent families of receptor molecules.

The Abundance and Behavioral Ecology of Cape Cod Gray Seals Under Predation Risk From White Sharks

The ultimate goal of wildlife recovery is abundance growth of a species, though it must also involve the reestablishment of the species’ ecological role within ecosystems frequently modified by humans. Reestablishment and subsequent recovery may depend on the species’ degree of adaptive behavior as well as the duration of their functional absence and the extent of ecosystem alteration. In cases of long extirpations or extensive alteration, successful reestablishment may entail adjusting foraging behavior, targeting new prey species, and encountering unfamiliar predatory or competitive regimes. Recovering species must also increasingly tolerate heightened anthropogenic presence, particularly within densely inhabited coastal zones. In recent decades, gray seals (Halichoerus grypus) recovered from exploitation, depletion, and partial extirpation in the Northwest Atlantic. On Cape Cod, MA, USA, gray seals have reestablished growing breeding colonies and seasonally interact with migratory white sharks (Carcarodon carcharias). Though well-studied in portions of their range due to concerns over piscivorous impacts on valuable groundfish, there are broad knowledge gaps regarding their ecological role to US marine ecosystems. Furthermore, there are few studies that explicitly analyze gray seal behavior under direct risk of documented shark predation.

In this dissertation, I apply a behavioral and movement ecology approach to telemetry data to understand gray seal abundance and activity patterns along the coast of Cape Cod. This coastal focus complements extensive research documenting and describing offshore movement and foraging behavior and allows me to address questions about movement decisions and risk allocation. Using beach counts of seals visible in satellite imagery, I estimate the total regional abundance of gray seals using correction factors from haul out behavior and demonstrate a sizeable prey base of gray seals locally. Analyzing intra-annual space use patterns, I document small, concentrated home ranges utilizing nearshore habitats that rapidly expand with shifting activity budgets to target disperse offshore habitats following seasonal declines in white sharks. During the season of dense shark presence, seals conducted abbreviated nocturnal foraging trips structured temporally around divergent use of crepuscular periods. The timing of coastal behavior with different levels of twilight indicate risk allocation patterns with diel cycles of empirical white shark activity. The emergence of risk allocation to explain unique behavioral and spatial patterns observed in these gray seals points to the importance of the restored predator-prey dynamic in gray seal behavior along Cape Cod.

Investigating the Structure of FtsZ to Understand its Functional Role in Bacterial Cell Division

FtsZ, a bacterial tubulin homologue, is a cytoskeleton protein that plays key roles in cytokinesis of almost all prokaryotes. FtsZ assembles into protofilaments (pfs), one subunit thick, and these pfs assemble further to form a “Z ring” at the center of prokaryotic cells. The Z ring generates a constriction force on the inner membrane, and also serves as a scaffold to recruit cell-wall remodeling proteins for complete cell division in vivo. FtsZ can be subdivided into 3 main functional regions: globular domain, C terminal (Ct) linker, and Ct peptide. The globular domain binds GTP to assembles the pfs. The extreme Ct peptide binds membrane proteins to allow cytoplasmic FtsZ to function at the inner membrane. The Ct linker connects the globular domain and Ct peptide. In the present studies, we used genetic and structural approaches to investigate the function of Escherichia coli (E. coli) FtsZ. We sought to examine three questions: (1) Are lateral bonds between pfs essential for the Z ring? (2) Can we improve direct visualization of FtsZ in vivo by engineering an FtsZ-FP fusion that can function as the sole source of FtsZ for cell division? (3) Is the divergent Ct linker of FtsZ an intrinsically disordered peptide (IDP)?

One model of the Z ring proposes that pfs associate via lateral bonds to form ribbons; however, lateral bonds are still only hypothetical. To explore potential lateral bonding sites, we probed the surface of E. coli FtsZ by inserting either small peptides or whole FPs. Of the four lateral surfaces on FtsZ pfs, we obtained inserts on the front and back surfaces that were functional for cell division. We concluded that these faces are not sites of essential interactions. Inserts at two sites, G124 and R174 located on the left and right surfaces, completely blocked function, and were identified as possible sites for essential lateral interactions. Another goal was to find a location within FtsZ that supported fusion of FP reporter proteins, while allowing the FtsZ-FP to function as the sole source of FtsZ. We discovered one internal site, G55-Q56, where several different FPs could be inserted without impairing function. These FtsZ-FPs may provide advances for imaging Z-ring structure by super-resolution techniques.

The Ct linker is the most divergent region of FtsZ in both sequence and length. In E. coli FtsZ the Ct linker is 50 amino acids (aa), but for other FtsZ it can be as short as 37 aa or as long as 250 aa. The Ct linker has been hypothesized to be an IDP. In the present study, circular dichroism confirmed that isolated Ct linkers of E. coli (50 aa) and C. crescentus (175 aa) are IDPs. Limited trypsin proteolysis followed by mass spectrometry (LC-MS/MS) confirmed Ct linkers of E. coli (50 aa) and B. subtilis (47 aa) as IDPs even when still attached to the globular domain. In addition, we made chimeras, swapping the E. coli Ct linker for other peptides and proteins. Most chimeras allowed for normal cell division in E. coli, suggesting that IDPs with a length of 43 to 95 aa are tolerated, sequence has little importance, and electrostatic charge is unimportant. Several chimeras were purified to confirm the effect they had on pf assembly. We concluded that the Ct linker functions as a flexible tether allowing for force to be transferred from the FtsZ pf to the membrane to constrict the septum for division.

Newly resolved relationships in an early land plant lineage: Bryophyta class Sphagnopsida (peat mosses).

UNLABELLED: PREMISE OF THE STUDY: The Sphagnopsida, an early-diverging lineage of mosses (phylum Bryophyta), are morphologically and ecologically unique and have profound impacts on global climate. The Sphagnopsida are currently classified in two genera, Sphagnum (peat mosses) with some 350-500 species and Ambuchanania with one species. An analysis of phylogenetic relationships among species and genera in the Sphagnopsida were conducted to resolve major lineages and relationships among species within the Sphagnopsida. • METHODS: Phylogenetic analyses of nucleotide sequences from the nuclear, plastid, and mitochondrial genomes (11 704 nucleotides total) were conducted and analyzed using maximum likelihood and Bayesian inference employing seven different substitution models of varying complexity. • KEY RESULTS: Phylogenetic analyses resolved three lineages within the Sphagnopsida: (1) Sphagnum sericeum, (2) S. inretortum plus Ambuchanania leucobryoides, and (3) all remaining species of Sphagnum. Sister group relationships among these three clades could not be resolved, but the phylogenetic results indicate that the highly divergent morphology of A. leucobryoides is derived within the Sphagnopsida rather than plesiomorphic. A new classification is proposed for class Sphagnopsida, with one order (Sphagnales), three families, and four genera. • CONCLUSIONS: The Sphagnopsida are an old lineage within the phylum Bryophyta, but the extant species of Sphagnum represent a relatively recent radiation. It is likely that additional species critical to understanding the evolution of peat mosses await discovery, especially in the southern hemisphere.

Studies in Aetiology and Historical Methodology in Herodotus

This dissertation interrogates existing scholarly paradigms regarding aetiology in the Histories of Herodotus in order to open up new avenues to approach a complex and varied topic. Since aetiology has mostly been treated as the study of cause and effect in the Histories, this work expands the purview of aetiology to include Herodotus’ explanations of origins more generally. The overarching goal in examining the methodological principles of Herodotean aetiology is to show the extent to which they resonate across the Histories according to their initial development in the proem, especially in those places that seem to deviate from the work’s driving force (i.e. the Persian Wars). Though the focus is on correlating the principles espoused in the proem with their deployment in Herodotus’ ethnographies and other seemingly divergent portions of his work, the dissertation also demonstrates the influence of these principles on some of the more “historical” aspects of the Histories where the struggle between Greeks and barbarians is concerned. The upshot is to make a novel case not only for the programmatic significance of the proem, but also for the cohesion of Herodotean methodology from cover to cover, a perennial concern for scholars of Greek history and historiography.

Chapter One illustrates how the proem to the Histories (1.1.0-1.5.3) prefigures Herodotus’ engagement with aetiological discussions throughout the Histories. Chapter Two indicates how the reading of the proem laid out in Chapter One allows for Herodotus’ deployment of aetiology in the Egyptian logos (especially where the pharaoh Psammetichus’ investigation of the origins of Egyptian language, nature, and custom are concerned) to be viewed within the methodological continuum of the Histories at large. Chapter Three connects Herodotus’ programmatic interest in the origins of erga (i.e. “works” or “achievements” manifested as monuments and deeds of abstract and concrete sorts) with the patterns addressed in Chapters One and Two. Chapter Four examines aetiological narratives in the Scythian logos and argues through them that this logos is as integral to the Histories as the analogous Egyptian logos studied in Chapter Two. Chapter Five demonstrates how the aetiologies associated with the Greeks’ collaboration with the Persians (i.e. medism) in the lead-up to the battle of Thermopylae recapitulate programmatic patterns isolated in previous chapters and thereby extend the methodological continuum of the Histories beyond the “ethnographic” logoi to some of the most representative “historical” logoi of Herodotus’ work. Chapter Six concludes the dissertation and makes one final case for methodological cohesion by showing the inextricability of the end of the Histories from its beginning.