My research has focused on field studies of complex social behavior by birds and other animals. Topics have included long-range vocal communication by temperate and tropical birds, vocal communication in noisy conditions (colonies, choruses, rainforests), sexual conflict and monogamy in territorial birds, sexual selection in polygynous mating systems and leks, site-specific dominance in wintering birds, and cooperative breeding in tropical wrens.
Continuing themes in all of these studies are age-dependent behavior, recognition of individuals, and impacts of noise on communication. My goal is to understand the complexity of animal social behavior … especially communication.
Facilities for this research include up-to-date equipment for recording, display, and synthesis of acoustic signals. My students, postdoctoral associates, and I have conducted field research both locally and far afield, including throughout the American tropics.
For more information, including publications, see http://rhwiley.bio.unc.edu.
Our research group is based in the Department of Biology at the The University at North Carolina at Chapel Hill. The research in our lab is focused on understanding and conserving the structure and dynamics of ocean ecosystems. We work in a variety of marine habitats including coral reefs, coastal wetland communities, oyster reefs and seagrass beds. Current projects include investigations of herbivory in the Galapagos Islands and Belize, the lionfish invasion of the Caribbean, patterns and dynamics of coral reef decline and recovery, the importance of predator biodiversity in estuarine food webs, salt marsh ecology and restoration, the effectiveness of tropical marine protected areas.
The research in our lab is centered on understanding the mechanisms and principles of cellular movement. Cytoskeletal filaments – composed of actin and microtubules – serve as a structural scaffolding that defines the architecture of the cytoplasm and gives cells the ability to divide, crawl, and change their shapes. We are interested in understanding how cells regulate cytoskeletal dynamics to produce motility. Our primary model system is the fruit fly, Drosophila melanogaster as it allows us to use functional genomic tools and classical genetic techniques to study gene function at the level of individual cells and during development. Current projects in the lab address mechanisms of microtubule dynamic instability, crosstalk between the actin and microtubule cytoskeletal networks, and the regulation of cellular contractility during Drosophila gastrulation.
Our lab group is interested in the behavior, sensory biology, neuroethology, and conservation of marine animals. Topics of particular interest include: (1) the navigation of long-distance ocean migrants such as sea turtles, salmon, spiny lobsters, and elephant seals; (2) magnetic field perception, magnetic maps, and use of the Earth’s magnetic field in animal navigation; (3) natal homing and the geomagnetic imprinting hypothesis in sea turtles and salmon; (4) applications of sensory ecology and movement ecology to conservation biology; (5) neurobiology, behavior, and physiology of marine invertebrates; (6) marine ecosystems and animal health in the Galapagos Islands. Techniques used range from electron microscopy, immunohistochemistry, and electrophysiology to behavioral studies, oceanographic modeling, and field studies in the ocean. Whenever possible, we favor innovative approaches that cut across traditional academic boundaries and combine elements from disparate fields.
Our lab group is interested in the sensory biology, behavior, neuroethology, and evolution of marine animals. Topics of particular interest include: (1) the navigation of long-distance ocean migrants such as sea turtles, salmon, and spiny lobsters; (2) magnetic field perception, magnetic maps, and use of the Earth’s magnetic field in animal navigation; (3) natal homing and the geomagnetic imprinting hypothesis in sea turtles and salmon; (4) applications of sensory ecology and movement ecology to conservation biology; (5) neurobiology, behavior, and physiology of marine invertebrates; (6) technoethology (the use of novel computer and electronic technology to study behavior). Techniques used range from electron microscopy, immunohistochemistry, and electrophysiology to behavioral studies, oceanographic modeling, and field studies in the ocean. Whenever possible, we favor innovative approaches that cut across traditional academic boundaries and combine elements from disparate fields.
Combining genetics with real-time analysis of living cells by video or digital enhanced microscopy to examine the role of dynein and other microtubule motor proteins in spindle and nuclear dynamics.
Using specific chromosomal or cytoskeletal perturbations to understand cell cycle control of late mitotic events.
Synopsis
Figure 1. Spindles are longer in histone depleted cells (kinetochores in green, SPBs in red).
Accurate chromosome segregation at each cell division is one of the most fundamental processes in a living organism. This complex process requires the coordination of cytoskeletal components such as microtubules and microtubule motor proteins that form the mitotic spindle with the replication and attachment of chromosomes to the segregation apparatus. Both the high fidelity of chromosome segregation and genome integrity are essential for normal development and cellular propagation. The ease of genetic and molecular manipulations to address the mechanism of chromosome segregation n the context of a live cell makes the budding yeast an excellent model system to address the mechanism of spindle assembly and the maintenance of genome integrity in mitosis. Our lab takes a broad approach to understanding mitosis in yeast. Recent projects in the lab have addressed the role of plus end microtubule binding proteins such as Bim1 and microtubule motor proteins on spindle integrity and the contribution of pericentric chromatin to regulating spindle length.
The site of microtubule attachment to the chromosome is the kinetochore, a complex of over 60 proteins assembled at a specific site on the chromosome, the centromere. Almost every kinetochore protein identified in yeast is conserved throughout phylogeny and the organization of the kinetochore in yeast may serve as the fundamental unit of attachment for mammalian cells. More recently we have become interested in the role of two different classes of ATP binding proteins, cohesions (Smc3, Scc1) and chromatin remodeling factors (Cac1, Hir1, Rdh54), in the structural organization of the kinetochore and how these classes of proteins contribute to the fidelity of chromosome segregation.
Chromosomes are compacted into increasingly complex chromatin structures within eukaryotic nuclei. High-throughput sequence-based assays have been developed to identify regions of nucleosome-depleted open chromatin that mark all types of regulatory elements genome-wide in tissues and cell-types. The computational integration of these data with related gene expression, transcription factor binding, and epigenetic data provide a more complete picture of the complex process of gene transcription and regulation. With these data, we are also investigating the effects of genetic variation on regulation, as can been seen through allelic imbalance in signal from chromatin and transcription factor data, as well as in quantitative trait loci (QTL)-based analyses of these data across individuals. Our computational biology lab both applies established analysis tools to data generated in collaboration with other labs as well as develops new analytical techniques to make novel associations.
Inflammatory Bowel Disease
Inflammatory bowel disease (IBD), primarily consisting of Crohn’s disease and ulcerative colitis, is the result of an inappropriate immune response to the intestinal microbiota in a genetically susceptible individual. We have partnered with Dr. Shehzad Sheikh, MD, PhD (Dept of Medicine, CGIBD) to uncover molecular and microbial characteristics of IBD disease phenotypes. We hypothesize that changes in the chromatin landscape in key intestinal cell types such as macrophages, are influenced by the host genetic background and significantly contribute to aberrant intestinal inflammation. Using both human tissue and mouse models, we seek to identify where chromatin is altered, the impacts on gene expression, the contributions of genetic variation, and the relationship to the microbial community in tissues and cells from affected individuals.
Environmental Toxicogenomics
Exposure to naturally occurring toxicants or by-products of manufacturing process can result in serious health challenges. We hypothesize that toxicant exposure can alter normal cellular function through changes in chromatin architecture and transcriptional profiles in tissues or cells contributing to the onset of medical complications. In a collaboration with Dr. Samir Kelada, PhD (Dept of Genetics), we are investigating the effects of exposure to ozone on the lung inflammatory response in the genetically diverse Collaborative Cross mouse model resource. In particular, we are assaying how ozone-induced chromatin structure and gene expression changes in alveolar macrophages, along with genetic variation, explain variability in ozone response.
Reproductive decisions are basic to all organisms. For species with multiple offspring and parental care, the decisions can be complex, but they still revolve around the same fundamental questions: when, where, and with whom to reproduce and how to invest in offspring. These decisions invariably have important life-history implications on future reproduction, on the offspring themselves, and on fitness.
Using birds, the Sockman lab studies the causes and consequences of reproductive decisions. Birds are an excellent system for this topic, because their decisions are often easy to observe and apply across a broad range of taxa and habitats. Follow the links above to learn more about our program or, if you are a prospective student, to learn about joining the lab.
FOR STUDENTS
If you want to list me as a reference or need a letter of recommendation, please use this guide from the UNC Biology Department website and include in your e-mail to me a PDF file of this document filled out and signed by you. Please see my laboratory website for other information.
Hormones influence virtually every aspect of plant growth and development. The elucidation of the molecular mechanisms controlling the biosynthesis and perception of these hormonal signals, and how these signals are integrated with each other and with other developmental and environmental signals remain fundamental questions in plant biology. There are three main areas of focus to the research in my laboratory: cytokinin signaling, the regulation of ethylene biosynthesis, and the regulation of cell elongation. Using a combination of genetic, molecular and biochemical approaches we are attempting to elucidate elements involved in these processes and ultimately to understand how these elements contribute to control plant growth and development.
Cytokinin Signal Transduction
Cytokinins were discovered by their property of promoting cell division. These N6-substituted adenine-based molecules have been associated with various developmental roles including germination, shoot and root development and leaf senescence. A model for cytokinin signal transduction has emerged that is similar to bacterial two-component systems (Fig. 1). Two-component elements in Arabidopsis are encoded by multi-gene families and similar families have been identified in the monocots maize and rice.
Figure 1: General model of cytokinin signaling. See: To and Kieber (2008), Trends in Plant Science, for details.
We seek to understand how these signaling elements interact with each other, how this pathway outputs to regulate the many processes that cytokinin regulates and to use mutants in various signaling components to further define the role of cytokinin in plant growth and development.
Regulation of Ethylene Biosynthesis
The simple gas ethylene has been recognized as a plant hormone since the turn of the century. It has been shown to influence a diverse array of plant processes, such as leaf and flower senescence and abscission, fruit ripening and the response to a wide variety of stresses. In order to understand how ethylene or any signaling molecule affects development, one must consider how its biosynthesis is controlled and the molecular mechanisms underlying its perception. Almost all plant tissues have the capacity to make ethylene, although in most cases the amount of ethylene produced is very low. There is a diverse group of factors that increase the level of ethylene biosynthesis, including other hormones (auxin, cytokinin, ethylene), numerous stresses, as well as various developmental events. We have taken a genetic approach to understanding how ethylene biosynthesis is regulated. Two classes of mutants have been isolated: those that overproduce ethylene (Eto mutants) and mutants that fail to increase ethylene biosynthesis in response to a specific inducer, cytokinin (Cin mutants). Together, these mutants identify elements involved in regulating ethylene biosynthesis. Studies from our lab have provided compelling evidence that ACS protein stability is regulated and have converged on a common mechanism. Research in our lab focuses on unraveling this mechanism regulating ACS protein stability. We are exploring the role of protein phosphorylation in this process. We are examining if the stability of ACS protein increases during developmental events that are associated with a rise in ethylene biosynthesis or in response to exogenous cues such as light. We are using various genetic screens to identify novel elements involved in controlling ACS protein stability. These studies will shed light on the mechanism regulating the regulation of the stability of ACC synthase proteins and how this contributes to the control of the biosynthesis of ethylene.
Regulation of Cell Expansion
The regulation of cell expansion is a primary determinant in the size and shape of plant organs. Understanding how cells regulate this process is crucial in understanding the development of plant form. The Arabidopsis root is an excellent model system to dissect this process as it has a relatively simple, well defined architecture and mutants that alter cell elongation can easily be identified by their effect on root length. In the root, two distinct regions of cell expansion can be distinguished. Both longitudinal and radial cell expansion occurs in the root apical meristem, defining the root diameter and moving cells into the elongation zone of the root. In the elongation zone, just above the meristem, elongation rates are also uniform, but are much higher and occur almost exclusively in the longitudinal direction. This polar cell expansion is known as anisotropy. Both the extent and orientation of cell expansion is regulated in plants. Cell expansion can be a dynamic process, and the orientation of expansion can change in response to various stimuli, such as wounding and hormonal treatments. Expansion of cells is driven by turgor pressure and the re
lative alignment and composition of cell wall material, which determines both the extent and orientation of elongation.
Figure 2: Phenotype of WT and AIK mutant seedlings. Note that the aik mutant root swells as a result of isotropic expansion of the root cells.
The plant cell wall is comprised of cellulose microfibrils that are crosslinked with glycans and are associated with a pectin matrix and various extracellular proteins. The primary load bearing elements of the cell wall are the cellulose microfibrils, and thus their orientation and crosslinking are key factors in both the direction and extent of cell expansion.In anisotropically elongating cells, the cellulose microfibrils are wound in a helical spiral transversely around the cell, in a manner that has been likened to hoops around a barrel. This arrangement allows expansion of the cell specifically in the longitudinal direction by stretching of this cellulose “spring”, but restricts expansion in the transverse or radial direction. Cellulose microfibrils are synthesized at the plasma membrane by a hexameric protein complex called the terminal complex or rosette, and the polysaccharides made by this complex are extruded into the extracellular space through some type of a pore in the plasma membrane, where they then associate with other cellulose chains to form microfibrils.
A major question regarding cell expansion is how is the deposition of the cellulose microfibrils is regulated to give, for example, primarily transverse microfibrils in root cells. Early studies revealed that the cytoplasmic microtubules were aligned transversely in some plant cells, correlated to the orientation of the cellulose microfibrils in those cells, and this and other data led to the idea that the microtubules act as a template for the synthesis of the cellulose microfibrils.
Our lab seeks to explore the links between ethylene, cell expansion and a pair of receptor-like kinase gene that we have evidence may link these processes. We identified a number a member of the leucine-rich receptor like Ser/Thr protein kinase (LRR-RLK) family in Arabidopsis (AIK1) that interacts with ACC synthase. Disruption of AIK results in Arabidopsis results in a plant in which the root cells lose their ability to elongation anisotropically. Further analysis suggests that ACC may act as a novel signal in this process. Molecular and genetic analysis has identified additional components in what now defines a novel regulatory circuit that controls the extend and orientation of cell expansion. These studies will shed light on how plants regulate both the extent and orientation of cell expansion and will help understand how the plant cell wall is constructed.
How do animals produce and control movement? How does a network of muscles, rigid elements and neurons – components of varying quality and with temporally varying responses – generate robust outputs in the face of uncertain circumstances? For example, the flight of the sphingid moth Manduca sexta is enabled by a complex, hierarchical biological system that involves processes and components at several different levels: the nervous system of the moth activates a suite of 20 flight muscles which actuate mechanical structures (the wings) that do work on the surrounding fluid (air), generating forces to support and propel the moth. These forces lead to changes in position and orientation which are detected by the sensory system and then used, along with underlying feedforward patterns as the basis for future muscle activation patterns, continuing the process and keeping the moth in the air.
Specific Areas of Research:
Aerodynamics of bird and insect flight
Neuromuscular and sensory control in animal flight
Computational approaches to organismal biomechanics
I apply both experimental and computational modeling approaches to these questions, iterating between the two approaches. For example, the figure below shows the wingbeat to wingbeat variation in wing motion during stable hovering flight for both a real moth and a computational model of the moth. In both the model and organism, steady flight behaviour requires continuous slight adjustments.
In addition to investigating the underlying variation of steady locomotion, I also make direct measurements from animals engaged in maneuvering or other unsteady movements. Figure 2 (below) outlines the basis of roll damping in the flapping flight of birds. Surprisingly high roll damping coefficients allow birds to control roll orientation with simple changes in wingbeat amplitude and passively dissipate roll velocity once symmetric flapping resumes.
