Biology Commons^™

Arabidopsis Msl10 Has A Regulated Cell Death Signaling Activity That Is Separable From Its Mechanosensitive Ion Channel Activity, Kira M. Veley, Grigory Maksaev, Elizabeth M. Frick, Emma January, Sarah C. Kloepper, Elizabeth S. Haswell

Biology Faculty Research

Members of the MscS superfamily of mechanosensitive ion channels function as osmotic safety valves, releasing osmolytes under increased membrane tension. MscS homologs exhibit diverse topology and domain structure, and it has been proposed that the more complex members of the family might have novel regulatory mechanisms or molecular functions. Here, we present a study of MscS-Like (MSL)10 from Arabidopsis thaliana that supports these ideas. High-level expression of MSL10-GFP in Arabidopsis induced small stature, hydrogen peroxide accumulation, ectopic cell death, and reactive oxygen species- and cell death-associated gene expression. Phosphomimetic mutations in the MSL10 N-terminal domain prevented these phenotypes. The phosphorylation …

A Central Support System Can Facilitate Implementation And Sustainability Of A Classroom-Based Undergraduate Research Experience (Cure) In Genomics, Jeremy Buhler, Elaine Mardis, Wilson Leung, Christopher Shaffer, Jennifer Threlfall, Sarah C.R. Elgin, David Lopatto, Charles Hauser, Christopher Jones, Don Paetkau, Vidya Chandrasekaran, David Dunbar, Christy Mackinnon, Joyce Stamm, Consuelo Alvarez, Daron Barnard, James Bedard, April Bednarski, Satish Bhalla, John Braverman, Martin Burg, Hui-Min Chung, Randall Dejong, Justin Diangelo, Chunguang Du, Todd Eckdahl, Julia Emerson, Amy Frary, Donald Frohlich, Anya Goodman, Yuying Gosser, Shubha Govind, Adam Haberman, Amy Hark, Arlene Hoogewerf, Diana Johnson, Lisa Kadlec, Marian Kaehler, Catherine Silver-Key, Nighat Kokan, Olga Kopp, Gary Kuleck, Jane Lopilato, Juan Martinez-Cruzado, Gerard Mcneil, Stephanie Mel, Alexis Nagengast, Paul Overvoorde, Susan Parrish, Mary Preuss, Laura Reed, Gloria Regisford, Dennis Revie, Srebrenka Robic, Jennifer Roecklien-Canfield, Anne Rosenwald, Michael Rubin, Kenneth Saville, Stephanie Schroeder, Karim Sharif, Mary Shaw, Gary Skuse, Christopher Smith, Mary Smith, Sheryl Smith, Eric Spana, Mary Spratt, Aparna Sreenivasan, Jeffrey Thompson, Matthew Wawersik, Michael Wolyniak, James Youngblom, Leming Zhou

Biology Faculty Research

In their 2012 report, the President's Council of Advisors on Science and Technology advocated "replacing standard science laboratory courses with discovery-based research courses"-a challenging proposition that presents practical and pedagogical difficulties. In this paper, we describe our collective experiences working with the Genomics Education Partnership, a nationwide faculty consortium that aims to provide undergraduates with a research experience in genomics through a scheduled course (a classroom-based undergraduate research experience, or CURE). We examine the common barriers encountered in implementing a CURE, program elements of most value to faculty, ways in which a shared core support system can help, and the …

A Seasonal, Density-Dependent Model For The Management Of An Invasive Weed, Esther Shyu, Eleanor A. Pardini, Tiffany M. Knight, Hal Caswell

Biology Faculty Research

The population effects of harvest depend on complex interactions between density dependence, seasonality, stage structure, and management timing. Here we present a periodic nonlinear matrix population model that incorporates seasonal density dependence with stage-selective and seasonally selective harvest. To this model, we apply newly developed perturbation analyses to determine how population densities respond to changes in harvest and demographic parameters. We use the model to examine the effects of popular control strategies and demographic perturbations on the invasive weed garlic mustard (Alliaria petiolata). We find that seasonality is a major factor in harvest outcomes, because population dynamics may …

Mechanisms For Regulation Of Plant Kinesins, Anindya Ganguly, Ram Dixit

Biology Faculty Research

Throughout the eukaryotic world, kinesins serve as molecular motors for the directional transport of cellular cargo along microtubule tracks. Plants contain a large number of kinesins that have conserved as well as specialized functions. These functions depend on mechanisms that regulate when, where and what kinesins transport. In this review, we highlight recent studies that have revealed conserved modes of regulation between plant kinesins and their non-photosynthetic counterparts. These findings lay the groundwork for understanding how plant kinesins are differentially engaged in various cellular processes that underlie plant growth and development.

Analysis Of Sry Duplications On The Rattus Norvegicus Y-Chromosome, Jeremy W. Prokop, Adam C. Underwood, Monte E. Turner, Nic Miller, Dawn Pietzrak, Sarah Scott, Chris Smith, Amy Milsted

Biology Faculty Research

Background: Gene copy number variation plays a large role in the evolution of genomes. In Rattus norvegicus and other rodent species, the Y-chromosome has accumulated multiple copies of Sry loci. These copy number variations have been previously linked with changes in phenotype of animal models such as the spontaneously hypertensive rat (SHR). This study characterizes the Y-chromosome in the Sry region of Rattus norvegicus, while addressing functional variations seen in the Sry protein products. Results: Eleven Sry loci have been identified in the SHR with one (nonHMG Sry) containing a frame shift mutation. The nonHMGSry is found and conserved in …

Microtubule Severing At Crossover Sites By Katanin Generates Ordered Cortical Microtubule Arrays In Arabidopsis, Quan Zhang, Erica Fishel, Tyler Bertroche, Ram Dixit

Biology Faculty Research

Highlights

• Severing primarily depolymerizes the overlying CMT at crossover sites
• Severing probability increases nonlinearly with crossover time
• Katanin localizes to crossover sites and is required for severing
• Loss of katanin activity prevents the formation of coaligned CMT arrays

Summary
The noncentrosomal cortical microtubules (CMTs) of land plants form highly ordered parallel arrays that mediate cell morphogenesis by orienting cellulose deposition [1, 2 and 3]. Since new CMTs initiate from dispersed cortical sites at random orientations [4], parallel array organization is hypothesized to require selective pruning of CMTs that are not in the dominant orientation. Severing of CMTs at crossover sites …

Colorful Displays Signal Male Quality In A Tropical Anole Lizard, E. G. Cook, Troy G. Murphy, Michele A. Johnson

Biology Faculty Research

Parasites influence colorful ornaments and their behavioral display in many animal hosts. Because coloration and display behavior are often critical components of communication, variation in these traits may have important implications for individual fitness, yet it remains unclear whether such traits are signals of quality in many taxa. We investigated the association between ectoparasitic mite load and the color and behavioral use of the throat fan (dewlap) by male Anolis brevirostris lizards. We found that heavily parasitized lizards exhibited lower body condition, duller dewlaps, and less frequent dewlap displays than less parasitized individuals. Our results thus suggest that highly parasitized …

Mscs-Like Mechanosensitive Channels In Plants And Microbes, Margaret E. Wilson, Grigory Maksaev, Elizabeth S. Haswell

Biology Faculty Research

The challenge of osmotic stress is something all living organisms must face as a result of environmental dynamics. Over the past three decades, innovative research and cooperation across disciplines have irrefutably established that cells utilize mechanically gated ion channels to release osmolytes and prevent cell lysis during hypoosmotic stress. Early electrophysiological analysis of the inner membrane of Escherichia coli identified the presence of three distinct mechanosensitive activities. The subsequent discoveries of the genes responsible for two of these activities, the mechanosensitive channels of large (MscL) and small (MscS) conductance, led to the identification of two diverse families of mechanosensitive channels. …

Heterochromatin Protein 1a (Hp1a) Partner Specificity Is Determined By Critical Amino Acids In The Chromo Shadow Domain And C-Terminal Extension, Deanna Lynn Mendez, Rebecca Mandt, Sarah C.R. Elgin

Biology Faculty Research

Drosophila melanogaster Heterochromatin Protein 1a (HP1a) is an essential protein critical for heterochromatin assembly and regulation. Its chromo shadow domain (CSD) homodimerizes, a requirement for binding protein partners that contain a PXVXL motif. How does HP1a select among its many different PXVXL-containing partners? HP1a binds tightly to Heterochromatin Protein 2 (HP2), but weakly to PIWI. We investigated differences in homodimerization and the impact of the C-terminal extension (CTE) by contrasting HP1a to its paralogue, HP1b. HP1a and HP1b differ in the dimerization interface, with HP1a having an Arg at position 188 rather than Glu. We find that while this substitution …

A Force Of Nature: Molecular Mechanisms Of Mechanoperception In Plants, Gabriele B. Monshausen, Elizabeth S. Haswell

Biology Faculty Research

The ability to sense and respond to a wide variety of mechanical stimuli-gravity, touch, osmotic pressure, or the resistance of the cell wall-is a critical feature of every plant cell, whether or not it is specialized for mechanotransduction. Mechanoperceptive events are an essential part of plant life, required for normal growth and development at the cell, tissue, and whole-plant level and for the proper response to an array of biotic and abiotic stresses. One current challenge for plant mechanobiologists is to link these physiological responses to specific mechanoreceptors and signal transduction pathways. Here, we describe recent progress in the identification …

The Rate And Effects Of Spontaneous Mutation On Fitness Traits In The Social Amoeba, Dictyostelium Discoideum, David W. Hall, Sara Fox, Jennie J. Kuzdzal-Fick, Joan E. Strassmann, David C. Queller

Biology Faculty Research

We performed a mutation accumulation (MA) experiment in the social amoeba Dictyostelium discoideum to estimate the rate and distribution of effects of spontaneous mutations affecting eight putative fitness traits. We found that the per-generation mutation rate for most fitness components is 0.0019 mutations per haploid genome per generation or larger. This rate is an order of magnitude higher than estimates for fitness components in the unicellular eukaryote Saccharomyces cerevisiae, even though the base-pair substitution rate is two orders of magnitude lower. The high rate of fitness-altering mutations observed in this species may be partially explained by a large mutational target …

Role Of Nucleation In Cortical Microtubule Array Organization: Variations On A Theme, Erica A. Fishel, Ram Dixit

Biology Faculty Research

The interphase cortical microtubules (CMTs) of plant cells form strikingly ordered arrays in the absence of a dedicated microtubule-organizing center. Considerable research effort has focused on activities such as bundling and severing that occur after CMT nucleation and are thought to be important for generating and maintaining ordered arrays. In this review, we focus on how nucleation affects CMT array organization. The bulk of CMTs are initiated from γ-tubulin-containing nucleation complexes localized to the lateral walls of pre-existing CMTs. These CMTs grow either at an acute angle or parallel to the pre-existing CMT. Although the impact of microtubule-dependent nucleation is …

Sexual Dimorphisms In Habitat-Specific Morphology And Behavior In The Green Anole Lizard, A K. Dill, T J. Sanger, A C. Battles, Michele A. Johnson

Biology Faculty Research

Species that occur in variable environments often exhibit morphological and behavioral traits that are specific to local habitats. Because the ability to move effectively is closely associated with structural habitat, locomotor traits may be particularly sensitive to fine-scale habitat differences. Anolis lizards provide an excellent opportunity to study the relationship between locomotion and natural perch use in the field, as laboratory studies have demonstrated that lizards that use broader perches develop longer limbs and have higher sprint speeds. We examined Anolis carolinensis (the green anole) in three habitats in close proximity. Our goals were to determine whether habitat-specific differences in …

Sexual Dimorphisms In Habitat-Specific Morphology And Behavior In The Green Anole Lizard, A K. Dill, T J. Sanger, Andrew C. Battles, Michele A. Johnson

Biology Faculty Research

Species that occur in variable environments often exhibit morphological and behavioral traits that are specific to local habitats. Because the ability to move effectively is closely associated with structural habitat, locomotor traits may be particularly sensitive to fine-scale habitat differences. Anolis lizards provide an excellent opportunity to study the relationship between locomotion and natural perch use in the field, as laboratory studies have demonstrated that lizards that use broader perches develop longer limbs and have higher sprint speeds. We examined Anolis carolinensis (the green anole) in three habitats in close proximity. Our goals were to determine whether habitat-specific differences in …

Plant Cytoskeleton: Della Connects Gibberellins To Microtubules, Ram Dixit

Biology Faculty Research

A new study reveals that DELLA proteins directly interact with the prefoldin complex, thus regulating tubulin subunit availability in a gibberellin-dependent manner. This finding provides a mechanistic link between the growth-promoting plant hormone gibberellin and cortical microtubule organization.

Targeting Heterochromatin Formation To Transposable Elements In Drosophila: Potential Roles Of The Pirna System, Monica F. Sentmanat, Sh Wang, Sarah C.R. Elgin

Biology Faculty Research

Successful heterochromatin formation is critical for genome stability in eukaryotes, both to maintain structures needed for mitosis and meiosis and to silence potentially harmful transposable elements. Conversely, inappropriate heterochromatin assembly can lead to inappropriate silencing and other deleterious effects. Hence targeting heterochromatin assembly to appropriate regions of the genome is of utmost importance. Here we focus on heterochromatin assembly in Drosophila melanogaster, the model organism in which variegation, or cell-to-cell variable gene expression resulting from heterochromatin formation, was first described. In particular, we review the potential role of transposable elements as genetic determinants of the chromatin state and examine how …

Recent Characterizations Of Mscs And Its Homologs Provide Insight Into The Basis Of Ion Selectivity In Mechanosensitive Channels, Grigory Maksaev, Elizabeth S. Haswell

Biology Faculty Research

The bacterial mechanosensitive channel MscS provides an excellent model system for the study of mechanosensitivity and for investigations into the cellular response to hypoosmotic shock. Numerous studies have elucidated the structure, function and gating mechanism of Escherichia coli MscS, providing a wealth of information for the comparative analysis of MscS family members in bacteria, archaea, fungi and plants. We recently reported the electrophysiological characterization of MscS-Like (MSL)10, a MscS homolog from the model flowering plant Arabidopsis thaliana. Here we summarize our results and briefly compare MSL10 to previously described members of the MscS family. Finally, we comment on how …

Effects Of Human Land Use On Prey Availability And Body Condition In The Green Anole Lizard, Anolis Carolinensis, Andrew C. Battles, Tara K. Whittle, Chelsea M. Stehle, Michele A. Johnson

Biology Faculty Research

Lizards frequently occur in disturbed habitats, yet the impacts of human activity on lizard biology remain understudied. Here, we examined the effects of land use on the body condition of Green Anole lizards (Anolis carolinensis) and the availability of their arthropod prey. Because human activity generally alters abiotic and biotic habitat features, we predicted that areas modified by humans would differ from areas with natural, intact vegetation in arthropod abundance and biomass. In addition, because biological communities in high use areas are often relatively homogenized, we predicted that higher human land use would result in lower prey diversity. Regardless of …

Plant-Pollinator Interactions Over 120 Years: Loss Of Species, Co-Occurrence, And Function, Laura A. Burkle, John C. Marlin, Tiffany M. Knight

Biology Faculty Research

Using historic data sets, we quantified the degree to which global change over 120 years disrupted plant-pollinator interactions in a temperate forest understory community in Illinois, USA. We found degradation of interaction network structure and function and extirpation of 50% of bee species. Network changes can be attributed to shifts in forb and bee phenologies resulting in temporal mismatches, nonrandom species extinctions, and loss of spatial co-occurrences between extant species in modified landscapes. Quantity and quality of pollination services have declined through time. The historic network showed flexibility in response to disturbance; however, our data suggest that networks will be …

Dictyostelium Development Shows A Novel Pattern Of Evolutionary Conservation, Xiangjun Tian, Joan E. Strassmann, David C. Queller

Biology Faculty Research

von Baer's law states that early stages of animal development are the most conserved. More recent evidence supports a modified "hourglass" pattern in which an early but somewhat later stage is most conserved. Both patterns have been explained by the relative complexity of either temporal or spatial interactions; the greatest conservation and lowest evolvability occur at the time of the most complex interactions, because these cause larger effects that are harder for selection to alter. This general kind of explanation might apply universally across independent multicellular systems, as supported by the recent finding of the hourglass pattern in plants. We …

Community And Ecosystem Effects Of Buffelgrass (Pennisetum Ciliare) And Nitrogen Deposition In The Sonoran Desert, Kelly G. Lyons, B. G. Maldonado-Leal, G. Owen

Biology Faculty Research

Buffelgrass is a non-indigenous, invasive, C₄ grass that was introduced throughout much of southern Texas, the Southwestern United States, and northern and central Mexico to improve degraded rangelands. The successful introduction and spread of buffelgrass follows a trajectory similar to that of other invasive C₄ grasses in arid and semiarid ecosystems. In the Plains of Sonora of the Sonoran Desert (Mexico) buffelgrass is favored by widespread removal of native vegetation and seeding, but, why, following initial introduction, the species persists remains unclear. In this study, we addressed two concerns associated with buffelgrass invasion in the Plains of Sonora. …

Aaron Gillette , Eugenics And The Nature Nurture Debate In The Twentieth Century, Garland E. Allen

Biology Faculty Research

Aaron Gillette, Eugenics and the Nature–Nurture Debate in the Twentieth Century, Palgrave Studies in the History of Science and Technology [2007], digital reprint (New York, NY: Palgrave Macmillan, 2010), pp. ix, 239, index, £18.99, paperback, ISBN: 9780230108455. This book treats an important subject – the history of the nature–nurture debate (focused on the US but with references to European players and movements) – and its implications for current theories of evolutionary psychology.

A New Social Gene In Dictyostelium Discoideum, Chtb, Lorenzo A. Santorelli, Adam Kuspa, Gad Shaulsky, David C. Queller, Joan E. Strassmann

Biology Faculty Research

BACKGROUND:

Competitive social interactions are ubiquitous in nature, but their genetic basis is difficult to determine. Much can be learned from single gene knockouts in a eukaryote microbe. The mutants can be competed with the parent to discern the social impact of that specific gene. Dictyostelium discoideum is a social amoeba that exhibits cooperative behavior in the construction of a multicellular fruiting body. It is a good model organism to study the genetic basis of cooperation since it has a sequenced genome and it is amenable to genetic manipulation. When two strains of D. discoideum are mixed, a cheater strain …

“Culling The Herd”: Eugenics And The Conservation Movement In The United States, 1900–1940, Garland E. Allen

Biology Faculty Research

While from a late twentieth- and early twenty-first century perspective, the ideologies of eugenics (controlled reproduction to eliminate the genetically unfit and promote the reproduction of the genetically fit) and environmental conservation and preservation, may seem incompatible, they were promoted simultaneously by a number of figures in the progressive era in the decades between 1900 and 1950. Common to the two movements were the desire to preserve the ‘‘best’’ in both the germ plasm of the human population and natural environments (including not only natural resources, but also undisturbed nature preserves such as state and national parks and forests). In …

Greater Sexual Reproduction Contributes To Differences In Demography Of Invasive Plants And Their Noninvasive Relatives, Jean H. Burns, Eleanor A. Pardini, Michele R. Schutzenhofer, Y Anny Chung, Katie J. Seidler, Tiffany M. Knight

Biology Faculty Research

An understanding of the demographic processes contributing to invasions would improve our mechanistic understanding of the invasion process and improve the efficiency of prevention and control efforts. However, field comparisons of the demography of invasive and noninvasive species have not previously been conducted. We compared the in situ demography of 17 introduced plant species in St. Louis, Missouri, USA, to contrast the demographic patterns of invasive species with their less invasive relatives across a broad sample of angiosperms. Using herbarium records to estimate spread rates, we found higher maximum spread rates in the landscape for species classified a priori as …

Maternal Depletion Of Piwi, A Component Of The Rnai System, Impacts Heterochromatin Formation In Drosophila, Tingting Gu, Sarah C.R. Elgin

Biology Faculty Research

A persistent question in epigenetics is how heterochromatin is targeted for assembly at specific domains, and how that chromatin state is faithfully transmitted. Stable heterochromatin is necessary to silence transposable elements (TEs) and maintain genome integrity. Both the RNAi system and heterochromatin components HP1 (Swi6) and H3K9me2/3 are required for initial establishment of heterochromatin structures in S. pombe. Here we utilize both loss of function alleles and the newly developed Drosophila melanogaster transgenic shRNA lines to deplete proteins of interest at specific development stages to dissect their roles in heterochromatin assembly in early zygotes and in maintenance of the silencing …

A Bacterial Symbiont Is Converted From An Inedible Producer Of Beneficial Molecules Into Food By A Single Mutation In The Gaca Gene, Pierre Stallforth, Debra A. Brock, Alexandra M. Cantley, Xiangjun Tian, David C. Queller, Joan E. Strassmann, Jon Clardy

Biology Faculty Research

Stable multipartite mutualistic associations require that all partners benefit. We show that a single mutational step is sufficient to turn a symbiotic bacterium from an inedible but host-beneficial secondary metabolite producer into a host food source. The bacteria's host is a "farmer" clone of the social amoeba Dictyostelium discoideum that carries and disperses bacteria during its spore stage. Associated with the farmer are two strains of Pseudomonas fluorescens, only one of which serves as a food source. The other strain produces diffusible small molecules: pyrrolnitrin, a known antifungal agent, and a chromene that potently enhances the farmer's spore production and …

Ornamental Bill Color Rapidly Signals Changing Condition, M. F. Rosenthal, Troy G. Murphy, N. Darling, K. A. Tarvin

Biology Faculty Research

Ornamental bill color is postulated to function as a condition-dependent signal of individual quality in a variety of taxonomically distant bird families. Most red, orange, and yellow bill colors are derived from carotenoid pigments, and carotenoid deposition in ornamentation may trade off with their use as immunostimulants and antioxidants or with other physiological functions. Several studies have found that bill color changes in response to physiological perturbations, but how quickly such changes can occur remains unclear. We tested the hypothesis that carotenoid-based orange bill color of American goldfinches Spinus tristis responds dynamically to rapid changes in physiological stress and reflects …

Nature And Function Of Insulator Protein Binding Sites In The Drosophila Genome, Yuri Schwartz, Daniela Linder-Basso, Peter Kharchenko, Michael Tolstorukov, Maria Kim, Hua-Bing Li, Andrey Gorchakov, Aki Minoda, Gregory Shanower, Artyom Alekseyenko, Nicole Riddle, Youngsook Jung, Tingting Gu, Annette Plachetka, Sarah C.R. Elgin, Mitzi Kuroda, Peter Park, Mikhail Savitsky, Gary Karpen, Vincenzo Pirrotta

Biology Faculty Research

Chromatin insulator elements and associated proteins have been proposed to partition eukaryotic genomes into sets of independently regulated domains. Here we test this hypothesis by quantitative genome-wide analysis of insulator protein binding to Drosophila chromatin. We find distinct combinatorial binding of insulator proteins to different classes of sites and uncover a novel type of insulator element that binds CP190 but not any other known insulator proteins. Functional characterization of different classes of binding sites indicates that only a small fraction act as robust insulators in standard enhancer-blocking assays. We show that insulators restrict the spreading of the H3K27me3 mark but …

Functions Of The Arabidopsis Kinesin Superfamily Of Microtubule-Based Motor Proteins, Chuanmei Zhu, Ram Dixit

Biology Faculty Research

Plants possess a large number of microtubule-based kinesin motor proteins. While the kinesin-2, 3, 9, and 11 families are absent from land plants, the kinesin-7 and 14 families are greatly expanded. In addition, some kinesins are specifically present only in land plants. The distinctive inventory of plant kinesins suggests that kinesins have evolved to perform specialized functions in plants. Plants assemble unique microtubule arrays during their cell cycle, including the interphase cortical microtubule array, preprophase band, anastral spindle and phragmoplast. In this review, we explore the functions of plant kinesins from a microtubule array viewpoint, focusing mainly on Arabidopsis kinesins. …