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Search Results: 1 - 10 of 192571 matches for " Aaron G. Greenup "
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Transcriptome Analysis of the Vernalization Response in Barley (Hordeum vulgare) Seedlings
Aaron G. Greenup,Sharyar Sasani,Sandra N. Oliver,Sally A. Walford,Anthony A. Millar,Ben Trevaskis
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017900
Abstract: Temperate cereals, such as wheat (Triticum spp.) and barley (Hordeum vulgare), respond to prolonged cold by becoming more tolerant of freezing (cold acclimation) and by becoming competent to flower (vernalization). These responses occur concomitantly during winter, but vernalization continues to influence development during spring. Previous studies identified VERNALIZATION1 (VRN1) as a master regulator of the vernalization response in cereals. The extent to which other genes contribute to this process is unclear. In this study the Barley1 Affymetrix chip was used to assay gene expression in barley seedlings during short or prolonged cold treatment. Gene expression was also assayed in the leaves of plants after prolonged cold treatment, in order to identify genes that show lasting responses to prolonged cold, which might contribute to vernalization-induced flowering. Many genes showed altered expression in response to short or prolonged cold treatment, but these responses differed markedly. A limited number of genes showed lasting responses to prolonged cold treatment. These include genes known to be regulated by vernalization, such as VRN1 and ODDSOC2, and also contigs encoding a calcium binding protein, 23-KD jasmonate induced proteins, an RNase S-like protein, a PR17d secretory protein and a serine acetyltransferase. Some contigs that were up-regulated by short term cold also showed lasting changes in expression after prolonged cold treatment. These include COLD REGULATED 14B (COR14B) and the barley homologue of WHEAT COLD SPECIFIC 19 (WSC19), which were expressed at elevated levels after prolonged cold. Conversely, two C-REPEAT BINDING FACTOR (CBF) genes showed reduced expression after prolonged cold. Overall, these data show that a limited number of barley genes exhibit lasting changes in expression after prolonged cold treatment, highlighting the central role of VRN1 in the vernalization response in cereals.
The Promoter of the Cereal VERNALIZATION1 Gene Is Sufficient for Transcriptional Induction by Prolonged Cold
Maria M. Alonso-Peral, Sandra N. Oliver, M. Cristina Casao, Aaron A. Greenup, Ben Trevaskis
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029456
Abstract: The VERNALIZATION1 (VRN1) gene of temperate cereals is transcriptionally activated by prolonged cold during winter (vernalization) to promote flowering. To investigate the mechanisms controlling induction of VRN1 by prolonged cold, different regions of the VRN1 gene were fused to the GREEN FLUORESCENT PROTEIN (GFP) reporter and expression of the resulting gene constructs was assayed in transgenic barley (Hordeum vulgare). A 2 kb segment of the promoter of VRN1 was sufficient for GFP expression in the leaves and shoot apex of transgenic barley plants. Fluorescence increased at the shoot apex prior to inflorescence initiation and was subsequently maintained in the developing inflorescence. The promoter was also sufficient for low-temperature induction of GFP expression. A naturally occurring insertion in the proximal promoter, which is associated with elevated VRN1 expression and early flowering in some spring wheats, did not abolish induction of VRN1 transcription by prolonged cold, however. A translational fusion of the promoter and transcribed regions of VRN1 to GFP, VRN1::GFP, was localised to nuclei of cells at the shoot apex of transgenic barley plants. The distribution of VRN1::GFP at the shoot apex was similar to the expression pattern of the VRN1 promoter-GFP reporter gene. Fluorescence from the VRN1::GFP fusion protein increased in the developing leaves after prolonged cold treatment. These observations suggest that the promoter of VRN1 is targeted by mechanisms that trigger vernalization-induced flowering in economically important temperate cereal crops.
Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphogenetic Basis of Human Origins
Aaron G. Filler
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0001019
Abstract: Background Despite the rising interest in homeotic genes, little has been known about the course and pattern of evolution of homeotic traits across the mammalian radiation. An array of emerging and diversifying homeotic gradients revealed by this study appear to generate new body plans and drive evolution at a large scale. Methodology/Principal Findings This study identifies and evaluates a set of homeotic gradients across 250 extant and fossil mammalian species and their antecedents over a period of 220 million years. These traits are generally expressed as co-linear gradients along the body axis rather than as distinct segmental identities. Relative position or occurrence sequence vary independently and are subject to polarity reversal and mirroring. Five major gradient modification sets are identified: (1)–quantitative changes of primary segmental identity pattern that appeared at the origin of the tetrapods ; (2)–frame shift relation of costal and vertebral identity which diversifies from the time of amniote origins; (3)–duplication, mirroring, splitting and diversification of the neomorphic laminar process first commencing at the dawn of mammals; (4)–emergence of homologically variable lumbar lateral processes upon commencement of the radiation of therian mammals and ; (5)–inflexions and transpositions of the relative position of the horizontal septum of the body and the neuraxis at the emergence of various orders of therian mammals. Convergent functional changes under homeotic control include laminar articular engagement with septo-neural transposition and ventrally arrayed lumbar transverse process support systems. Conclusion/Significance Clusters of homeotic transformations mark the emergence point of mammals in the Triassic and the radiation of therians in the Cretaceous. A cluster of homeotic changes in the Miocene hominoid Morotopithecus that are still seen in humans supports establishment of a new “hominiform” clade and suggests a homeotic origin for the human upright body plan.
Review of Quantitative Reasoning: Tools for Today's Informed Citizen by A. Sevilla and K. Somers
Aaron G. Montgomery
Numeracy , 2008,
Abstract: Alicia Sevilla and Kay Somers, Quantitative Reasoning: Tools for Today’s Informed Citizen. (Emeryville CA: Key College Publishing, 2007). 626 pp. Softcover with Student CD. $79.95 (USA) ISBN 1-931914-90-1. http://www.keycollege.com/catalog/titles/quantitative_reasoning.htmlFrom charts and graphs (Topic 1) to decision making (Topic 21), Quantitative Reasoning offers a good selection of topics that students in a general education mathematics course and other individuals in our society should understand. Organizing the 21 chapters (topics) under the headings of numerical reasoning, logical reasoning, and statistical reasoning, Sevilla and Somers focus their chapters on examples and devote the last 224 pages to 21 Excel activities. Parallel graphic-calculator activities are on the Student CD, together with the data bank for the Excel activities. The strong orientation toward exercises and activities will assist instructors in making their course an engaging numeracy experience for their students; however, it also likely means that some instructors will find that some explanations are not as fully developed as they would like. With the selection, structure, exercises and activities provided by Sevilla and Somers, instructors can easily add supplemental material according to their own interests and priorities.
Review of Sex, Drugs and Body Counts: The Politics of Numbers in Global Crime and Conflict, edited by Peter Andreas and Kelly M. Greenhill
Aaron G. Montgomery
Numeracy , 2011,
Abstract: Andreas, Peter, and Greenhill, Kelly M. (Eds.). Sex, Drugs, and Body Counts: The Politics of Numbers in Global Crime and Conflict, (Ithaca, NY: Cornell University Press, 2010). 287 pp. ISBN 978-0-8014-4861-4 (cloth); ISBN 978-0-8014-7618-1 (pbk).The ten scholarly papers in Sex, Drugs and Body Counts explore the generation and propagation of numbers that drive policy decisions in the U.S. government regarding human trafficking, drug trade, and armed conflict (including the war on terror). Each of these papers, written by different authors, provides an illuminating insight into how some of the numbers we hear or read in the news are derived. While the general message of the papers tends to be depressing, namely that the numbers driving U.S. policy vary from being slightly suspect to clearly fabricated, the book does provide positive examples of how accurate numbers can be obtained and how the numbers that are being used can be interpreted. As a teaching resource, the book provides instructors an opportunity to deepen their understanding of how quantitative data are used in U.S. policy, allowing them to explore these issues in class. Individual papers from the book could be used in a general education course (either in mathematics or in a field related to the topics) as a way to introduce students to reading quantitatively dense material. In a course more focused on the topics of the book and with a more quantitatively literate audience, the entire book could probably be assigned as reading.
Disorders caused by chromosome abnormalities
Aaron Theisen, Lisa G Shaffer
The Application of Clinical Genetics , 2010, DOI: http://dx.doi.org/10.2147/TACG.S8884
Abstract: orders caused by chromosome abnormalities Review (7654) Total Article Views Authors: Aaron Theisen, Lisa G Shaffer Published Date December 2010 Volume 2010:3 Pages 159 - 174 DOI: http://dx.doi.org/10.2147/TACG.S8884 Aaron Theisen Lisa G Shaffer Signature Genomic Laboratories, Spokane, WA, USA Abstract: Many human genetic disorders result from unbalanced chromosome abnormalities, in which there is a net gain or loss of genetic material. Such imbalances often disrupt large numbers of dosage-sensitive, developmentally important genes and result in specific and complex phenotypes. Alternately, some chromosomal syndromes may be caused by a deletion or duplication of a single gene with pleiotropic effects. Traditionally, chromosome abnormalities were identified by visual inspection of the chromosomes under a microscope. The use of molecular cytogenetic technologies, such as fluorescence in situ hybridization and microarrays, has allowed for the identification of cryptic or submicroscopic imbalances, which are not visible under the light microscope. Microarrays have allowed for the identification of numerous new syndromes through a genotype-first approach in which patients with the same or overlapping genomic alterations are identified and then the phenotypes are described. Because many chromosomal alterations are large and encompass numerous genes, the ascertainment of individuals with overlapping deletions and varying clinical features may allow researchers to narrow the region in which to search for candidate genes.
Bedside Teaching in Australian Clinical Schools: A National Study
Praveen L. Indraratna,Louise C. Greenup,Timothy X. Yang
Journal of Biomedical Education , 2013, DOI: 10.1155/2013/948651
Abstract: Purpose. Bedside teaching (BST) of medical students has become less common in recent years; however, there have been strong recommendations made in the literature to continue this teaching modality for the valued benefits it provides. The purpose of the present study is to explore the perceptions and opinions of bedside teaching among senior Australian medical students. Methods. Medical students at Australian universities were surveyed by means of an electronic questionnaire. The results were collected and analysed. Results. A total of 517 responses were received from students at 15 universities and 94 different clinical sites. The percentage of students who identified BST as very important ranged from 62.5% in psychiatry to 90.4% in internal medicine. The optimal class size was nominated as 3-4 students, and students favoured a style where one individual performs a complete examination, with the remainder allowed to elicit the key sign afterwards. Students felt 3-4 hours of BST per week to be ideal. Advantages identified to BST included provision of feedback and elicitation of clinical signs. Disadvantages included time constraints and excessive class sizes. Conclusions. The unique benefits of BST result in its high demand by students, regardless of the discipline being taught. 1. Introduction Bedside teaching (BST), defined as when a clinician supervises a group of students at the patient’s bedside to elicit a history or physical signs, was once the most common form of medical student teaching [1]. It is currently, however, seen primarily as an adjunctive teaching method to classroom-based and informal teaching. Documented reasons for this include time constraints on tutors, increasing reliance on biochemical testing, medical imaging, and consultation of subspecialists [1–3]. Despite this, medical students still desire BST, and anecdotal reports have described declining amounts of this particular teaching modality and, in some centres, a total lack thereof. The opinions and perceptions of current medical students regarding this teaching modality, however, remain largely unpublished. The present study is the largest survey of students’ opinions and perceptions on BST, and it has targeted a multi-institutional population across the nation. Factors analysed included students’ opinions on optimal class size, time devoted to BST, and teaching style, as well as the importance of BST within various medical disciplines. 2. Methods Ethical approval was granted by the University of New South Wales Human Research and Ethics Advisory Panel (ref: AD 11066). 2.1.
The bearing of biological fitness in humans and crops upon the emergence and spread of agriculture  [PDF]
Aaron Rottenberg
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.54A001
Abstract:

Past studies discussing the origins of agriculture have mainly emphasized changes in environmental and human-behavior factors as possible explanations for the shift from foraging to farming. This paper focuses on how increase in the biological fitness of both farmers and crops enabled the rapid evolution and success of farmers and agriculture. It is shown that the first plants under domestication achieved their superior fitness mainly as a consequence of some of their genetic and life-history traits. It led these species to be extensively integrated into human subsistence and eventually dominate the farmers’ fields. Concurrently, the first farmers gained their enhanced fitness by producing food surplus and by acquiring extra social prestige and power, while materializing the tendency to higher reproduction rate, and eventually to the expansion of farming populations. The unbreakable dependence between high fitness crops and high fitness man, namely their coevolution is a key issue and a promising research area in the understanding of the human story and the origins of agriculture.

Altered Fire Regimes and the Persistence of Quaking Aspen in the Rocky Mountains: A Literature Review  [PDF]
Aaron Rosenblum
Open Journal of Forestry (OJF) , 2015, DOI: 10.4236/ojf.2015.55050
Abstract: The persistence of quaking aspen (Populus tremuloides Michx.) is of significant importance to land managers in the Rocky Mountain region. Fire suppression in the past century has been implicated as a mechanism influencing aspen population dynamics, as aspen are generally considered an early seral disturbance adapted species. The heterogeneity of aspen community assemblages and fire regimes makes it difficult to discern what the result of fire suppression has been at large spatial and temporal scales. Decision makers should investigate the questions at hand at the stand level in their study location to best determine the mechanisms at play, as well as consider future potential changes to the system.
The advantages and disadvantages of horizontal gene transfer and the emergence of the first species
Aaron A Vogan, Paul G Higgs
Biology Direct , 2011, DOI: 10.1186/1745-6150-6-1
Abstract: We study a model for genome evolution that incorporates both beneficial and detrimental effects of HGT. We show that if rate of gene loss during genome replication is high, as was probably the case in the earliest genomes before the time of the last universal common ancestor, then a high rate of HGT is favourable. HGT leads to the rapid spread of new genes and allows the build-up of larger, fitter genomes than could be achieved by purely vertical inheritance. In contrast, if the gene loss rate is lower, as in modern prokaryotes, then HGT is, on average, unfavourable.Modern cells should therefore evolve to reduce HGT if they can, although the prevalence of independently replicating mobile elements and viruses may mean that cells cannot avoid HGT in practice. In the model, natural selection leads to gradual improvement of the replication accuracy and gradual decrease in the optimal rate of HGT. By clustering genomes based on gene content, we show that there are no separate lineages of organisms when the rate of HGT is high; however, as the rate of HGT decreases, a tree-like structure emerges with well-defined lineages. The model therefore passes through a Darwinian Threshold.This article was reviewed by Eugene V. Koonin, Anthony Poole and J. Peter Gogarten.Traditionally, genetics is the study of vertical transmission of genes from parents to offspring. Since complete genomes have become available, it has become clear that, in addition to vertical inheritance, there is a substantial rate of horizontal gene transfer (HGT) from unrelated individuals, at least in prokaryotes. According to the principle of natural selection, if a gene increases the fitness of an individual, that individual will have a larger number of offspring on average, and the offspring will inherit the beneficial gene. Hence, the frequency of the beneficial gene will increase in the population. It is therefore clear that vertical inheritance of genes allows natural selection to occur. In contrast, if
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