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Allan M. Showalter

Allan Showalter

Professor

Environmental & Plant Biology
Porter Hall 504
showalte@ohio.edu
740-593-1135
740-593-1130

Recent News

Education
Research
Current & Recent Research Projects
Courses Taught
Professional Experience
Awards & Honors
Research Publications
Book Publications
Departmental Service
Scientific Societies & Board Memberships
Showalter Lab Students, Graduate Students and Advisees
Funding

Education

Ph.D., Rutgers University, 1983

Postdoctoral (Plant Molecular Biology), Washington University, St. Louis, MO    1983-1986

Ph.D. (Biochemistry), Rutgers University and the University of Medicine and Dentistry of New Jersey, Rutgers Medical School, New Brunswick, NJ    1983

B.A. (Biology), Franklin & Marshall College, Lancaster, PA    1978

Research

  • Molecular Biology and Biochemistry
Research Interests

Structure, biosynthesis and function of plant cell wall hydroxyproline-rich glycoproteins as revealed by molecular biology and biochemical studies. Particular interest in the extensins, solanaceous lectins, and arabinogalactan-proteins. Additional interests in plant DNA barcoding and the molecular and biochemical mechanisms of salt tolerance utilized by halophytes.

Structure, Expression and Function of Plant Cell Wall Proteins

Research in my lab is directed at elucidating the structure, expression, and function of the superfamily of hydroxyproline-rich glycoproteins (HRGPs) found in plant cell walls. HRGPs represent the major protein components of the plant cell surface (i.e., the plant cell wall and plasma membrane) and include the arabinogalactan-proteins (AGPs), extensins (EXTs), proline-rich proteins (PRPs), and solanaceous lectins. Using a variety of molecular biology techniques, we have isolated and characterized a number of cDNA and genomic clones encoding these cell surface proteins. Moreover, we have used these clones as molecular probes to examine the regulated expression of these genes during development and in response to various stress conditions such as wounding, pathogen infection, and drought. Biochemical studies are underway to determine the molecular interactions that these proteins undergo once deposited at the cell surface. Current efforts to alter the expression of these HRGPs in plants using a variety of techniques (antisense RNA, RNA interference, insertional mutagenesis, overexpression, expression of fusion proteins) in transgenic plants is also underway in order to elucidate their expression, molecular interactions, and functions. We have expressed a GFP-arabinogalactan-protein fusion in transgenic plants and used it to demonstrate that this particular arabinogalactan-protein is attached to the outer leaflet of the plasma membrane via a glycosylphosphatidylinositol (GPI) lipid anchor. We have also established a link between arabinogalactan-proteins and programmed cell death in plants. Our recent work makes use of the genetic model plant, Arabidopsis thaliana, in which we are studying various AGP mutants to elucidate AGP function and also isolating the enzymes (and the genes) responsible for glycosylating AGPs and other HRGPs. Our research on arabinogalactan-proteins uses many experimental approaches (i.e., molecular genetics, molecular biology, biochemistry, functional genomics, cell biology, plant physiology) and is supported by NSF and USDA grants.

Bioinformatics of Plant Cell Wall Proteins

Research in my lab also uses a bioinformatic approach to the identification and characterization of plant cell wall hydroxyproline-rich glycoproteins (HRGPs). Initially, Arabidopsis was used as the model organism for this work; now other plant genomes/proteomes are being examined. This bioinformatics work complements the lab bench work that we do on HRGPs and relates to the evolution of the HRGP superfamily and to the evolution of plants.

Molecular Adaptations of Halophytes to Saline Environments

Another project in the lab involves examining the molecular adaptations of halophytes to saline environments. Here, Atriplex prostrata, a plant that thrives in saline environments, is being examined with respect to its physiological and molecular responses to growth under various salt concentrations. We are particularly interested in the role which glycinebetaine plays as an osmoprotectant. Consequently, we have cloned the genes that encode the pathway for the synthesis of glycinebetaine for the purpose of genetically engineering crop plants to survive in saline soils.

Agricultural Nanofertilizers to Enhance Growth and Drought Tolerance of Plants

A new project in the lab involves testing the hypothesis that agricultural nanofertilizers can improve the growth and drought tolerance of plants in order to feed the ever increasing human population and deal with climate change. Specific nanofertilizers will be administered to plants grown in environmental chambers under normal conditions and under drought conditions. Plants grown with standard chemical fertilizers will be used as controls. Plants will be monitored weekly for standard growth and developmental parameters (i.e., germination time, germination efficiency, plant height, leaf number, root length, flowering time, fruiting time, total seed yield, etc.), and subjected to statistical analysis to determine differences among the plant groups. We hypothesize that the plants grown with one or more of the nanofertilizers will show superior growth and productivity, particularly under drought conditions. Future work will involve producing and testing additional nanofertilizers, conducting greenhouse and field studies, and expanding work to include additional crop plants.

Medicinal Plants: DNA Barcoding and Drug Discovery

My lab is also involved with another project using DNA Barcoding to uniquely identify medical plants that are used in Pakistan and elsewhere in the world. DNA is extracted from such plants provided by our Pakistani collaborators; then particular chloroplast DNA sequences (e.g. rbcL and matK) are amplified using the polymerase chain reaction (PCR) and sequenced to generate a DNA Barcode. This work is designed to verify that the proper medicinal plants are being used by medicinal plant industries and to insure that samples are not contaminated or adulterated with undesirable or harmful plant species. This work is now being expanded to include the extraction and identification of bioactive compounds from selected medicinal plants to treat human diseases, such as cancer and diabetes.

Faculty Research Focus Area: Plant Cell Wall Biotechnology

Current and Recent Research Projects

  • Isolation and characterization of the enzymes and genes responsible for glycosylating arabinogalactan-proteins (AGPs) and other hydroxyproline-rich glycoproteins (HRGPs).
  • A bioinformatics approach to the identification, classification, and analysis of plant cell wall HRGPs.
  • Molecular, cellular, biochemical, and physiological characterization of genetic mutants in AGP genes and AGP glycosyltransferase genes to elucidate AGP function.
  • DNA barcoding of medicinal plants used in Pakistan.

Courses Taught

Professional Experience

  • 2011-2012 Chair, Department of Environmental and Plant Biology, Ohio University, Athens, OH
  • 1999-2000 Senior Fellow, School of Botany, The University of Melbourne, 1999-2000
  • 1998-present Professor, Department of Environmental and Plant Biology and the Molecular and Cellular Biology Program, Ohio University, Athens, OH
  • 1993-1996 Chair, Molecular and Cellular Biology Program, Ohio University, Athens, OH
  • 1992-1998 Associate Professor, Department of Environmental and Plant Biology and the Molecular and Cellular Biology Program, Ohio University, Athens, OH
  • 1986-1992 Assistant Professor, Department of Environmental and Plant Biology and the Molecular and Cellular Biology Program, Ohio University, Athens, OH
  • 1983-1986 Research Associate (postdoctoral fellow) at Washington University, St. Louis, MO in the laboratory of Dr. Joseph E. Varner studying hydroxyproline-rich glycoproteins (extensins)
  • 1979-1983 Research Assistantship at the Rutgers Medical School to isolate and characterize chick cDNAs coding for types I and II procollagen under the direction of Dr. Bjorn R. Olsen
  • 1979 Teaching Assistantship for an introductory undergraduate Biochemistry course and a graduate Biochemistry course
  • 1977-1978 Undergraduate senior research thesis on phytochrome control of hydroxyproline metabolism in Pisum sativum under the direction of Dr. Carl S. Pike

Awards and Honors

  • Invited to serve on the Scientific Session Committee for the XIII Cell Wall Meeting, Crete 2016
  • Invited Speaker at the XIV International Plant Cell Wall Meeting, Crete 2016
  • Invited Speaker at the 2nd International Conference on Salt Tolerance, Doha, 2013
  • Invited Speaker at the 6th International Barcode of Life Conference, Guelph, 2015
  • Invited Speaker at the at the Gordon Research Conference on Plant Cell Walls, Boston, 2015
  • Invited Speaker at the 5th International Barcode of Life Conference, Kunming, 2013
  • Invited Speaker at the XIII International Plant Cell Wall Meeting, Nantes 2013
  • Invited Speaker at the Society for Experimental Biology Meeting, Valencia 2013
  • Invited Speaker at the Pakistan-US Science and Technology Cooperation Program Technology Transfer Symposium, Islamabad, 2013
  • Invited Session Organizer and Speaker at the International Botanical Congress, Melbourne 2011
  • Co-Organizer and Speaker at an international workshop on “Medicinal Plants: Conservation and Sustainable Use”, Islamabad 2011
  • Invited Speaker at the Pakistan-U.S. Science and Technology Conference in Dubai, 2011
  • Invited to serve on the Scientific Organizing Committee for the XII Cell Wall Meeting, Porto 2010
  • Elected Chair (2009-2011) and Vice Chair (2008-2009), Ohio Plant Biotechnology Consortium
  • Invited Speaker at the XI International Plant Cell Wall Meeting, Copenhagen 2007
  • Invited Session Organizer and Speaker at the International Botanical Congress, Vienna 2005
  • Elected to serve on the American Society of Plant Biologists (ASPB) Executive Committee (2004-2007) and as the ASPB Midwest Section representative (2004-2007)
  • Invited Speaker at the X International Plant Cell Wall Meeting, Sorrento 2004
  • Invited Speaker at the Gordon Research Conference on Plant Cell Walls, 2003
  • Chair (2003-04) & Vice-chair (2002-03), American Society of Plant Biologists (Midwest Section)
  • Executive Committee for the Ohio Plant Biotechnology Consortium (OPBC), 2001-present
  • Invited Speaker at the IX International Plant Cell Wall Meeting, Toulouse 2001
  • Invited to serve on the Scientific Organizing Committee for the IX Cell Wall Meeting, Toulouse 2001
  • Served as editor and contributor to a collection of plant cell wall proteins manuscripts published by Cellular and Molecular Life Sciences, 2000-2001
  • Invited Instructor for an Advanced Course on Stress, Programmed Cell Death and Signaling in Plants & Speaker for a Cell Death Workshop, Instituto de Biologia Molecular e Celular, Porto 2000
  • Appointed Honorary Senior Fellow, School of Botany, The University of Melbourne, 1999-2000
  • Invited Session Organizer and Speaker at the International Botanical Congress, St. Louis 1999
  • Invited Speaker and Discussion Leader at the 20th Symposium in Plant Physiology, 1999
  • Invited Speaker at the VIII International Plant Cell Wall Meeting, Norwich 1998
  • Invited Session Chair and Speaker at the Gordon Research Conference on Plant Cell Walls, 1997
  • Invited Speaker at the Keystone Symposium on The Extracellular Matrix of Plants, 1996
  • Invited Speaker at the VII International Plant Cell Wall Meeting, Santiago de Compostela 1995
  • Invited Session Organizer and Speaker at the International Botanical Congress, Tokyo/Yokohama 1993
  • Invited Speaker at the VI International Plant Cell Wall Meeting, Nijmegen 1992
  • Invited Speaker at the Third International Congress of Plant Molecular Biology on "Molecular Biology of Higher Plant HRGPs", Tucson 1991
  • Invited Speaker at the Annual Meeting of the American Society of Plant Physiologists on "Extensin Family Members and Their Relatives", Albuquerque 1991
  • Invited Speaker at the American Society of Cell Biology Conference on "Biology of Plant and Animal Extracellular Matrix", 1990
  • Invited Speaker at the Gordon Research Conference on "Plant Molecular Biology", 1987
  • Invited Speaker at a Univ. of Wisconsin symposium on "Plant Genes of Economic Interest", 1986
  • Invited Speaker at the NATO Advanced Research Workshop on "Biology and Molecular Biology of Plant-Pathogen Interactions", Ilminster, U.K. 1985
  • Johnson & Johnson Fellowship (Competitive), 1981-1982
  • Graduated cum laude from Franklin & Marshall College with Honors in Biology, 1978

Research Publications

Much of this research was supported by the National Science Foundation (NSF) under grants IBN-0110413 and IBN-9727757; however, “any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.”

Book Publications

  • Showalter, A. M. and K. M. Thompson (2016) BIOLOGY 1010 LABORTORY MANUAL – 3rd Edition. Van-Griner Publishing, Cincinnati, Ohio, ISBN: 978-1-61740-329-3, 157 pp.
  • Showalter, A. M. (2014) BIOLOGY 1010 LABORTORY MANUAL – 2nd Edition. Van-Griner Publishing, Cincinnati, Ohio, ISBN: 978-1-61740-131-2, 152 pp.
  • Showalter, A. M. (2013) BIOLOGY 1010 LABORTORY MANUAL. Van-Griner Publishing, Cincinnati, Ohio, ISBN: 978-1-61740-070-4, 154 pp.

Departmental Service

  • Promotion & Tenure Committee, Chair
  • Evaluation Committee, Chair

Scientific Societies & Board Memberships

Professional Scientific Society Memberships:
Editorial Boards

Showalter Lab Students, Graduate Students and Advisees

Current Graduate Students, Undergraduate Students, and Post-Docs in the Showalter Lab

  • Xiao Liu (Ph.D. student)
  • Oyeyemi Ajayi (Ph.D. student)
  • Dasmeet Kaur (Ph.D. student)
  • Tristan Hoffman (undergraduate student)
  • Dylan Torok (undergraduate student)
  • David Masters (undergraduate student)
  • Dr. Melanie Schori (post-doc, completed lab work and now preparing 3 manuscript submissions)

Graduate Students Advised (19)

Graduate Student |  Year |  Degree |  Dissertation/Thesis Title
  • Debarti Basu    (2015)    PhD   Identification and Characterization of Five Arabidopsis Hydroxyproline Galactosyltransferases and Their Functional Roles in Arabinogalactan-Protein Glycosylation, Growth, Development, and Cellular Signaling
  • Lu Tian    (2015)    MS   Characterization of Genetic Mutants Encoding Four Hydroxyproline Galactosyltransferases (Hyp-GALTs) for Arabinogalactan-Proteins in Arabidopsis
  • Yan Liang    (2012)    PhD   Identification and Characterization of Galactosyltransferases and Fucosyltransferases Involved in Arabinogalactan-Protein Glycosylation
  • Brian D. Keppler    (2010)    MS   IRX14 and IRX14-LIKE: Two Glycosyl Transferases involved in Glucuronoxylan Biosynthesis in Arabidopsis
  • Yizhu Zhang    (2008)    PhD   Functional Characterization of Lysine-rich Arabinogalactan-Proteins (AGPs) and an AG Peptide in Arabidopsis
  • Harjinder Sardar    (2007)    PhD   Molecular Interactions of Arabinogalactan-Proteins (AGPs) in Tobacco Bright Yellow-2 Cultured Cells and Functional Identification of Four Classical AGPs in Arabidopsis
  • Yang Jie    (2007)    PhD   Functional Identification of Three Lysine-Rich Arabinogalactan-Proteins (AGPs) in Arabidopsis
  • Sarah Bashore    (2006)    PhD   Characterization of a Spontaneous Phaseolus Vulgaris Mutant with the Ability to Selectively Restrict Nodulation
  • Wenxian Sun    (2004)    PhD   Structure, expression and function of the tomato LeAGP-1 arabinogalactan protein and its homologs in Arabidopsis
  • Ming Chen    (2004)    PhD   Programmed cell death induced by perturbing the function of arabinogalactan-protein by Yariv reagent
  • Li-Wen Wang    (2002)    PhD   Cloning and Characterization of Genes Related to Betaine, the Effect of Salt on Cell Death and Competition on Atriplex Prostrata
  • Ming-geng Gao    (1999)    PhD   Structure, localization and function of a modular, tomato arabinogalactan-protein
  • Ayyappan Nair    (1997)    PhD   A wound-inducible peroxidase and oxidative burst in carrots
  • Shu-Xia Li    (1996)    PhD   Isolation and characterization of genes and complementary DNAs encoding tomato arabinogalactan protein
  • Grattan Welch    (1996)     MS   An analysis of glycine-rich protein and extensin genes in tomato (Lycopersicon esculentum) and potato (Solanum tumberosum L.)
  • Li-Wen Wang    (1996)    MS   The effects of salinity on growth and ion content of Atriplex triangularis
  • Zhixiong Yuan    (1994)    MS   Isolation and characterization of cDNA and genomic clones encoding potato tuber lectin and potato extensin
  • Tsai Tzong-Lin    (1992)    MS   Isolation and characterization of potato tuber lectin and potato extensin cDNA clones
  • Jin Zhou    (1991)    PhD   Isolation and characterization of cDNA and genomic DNA clones encoding tomato hydroxyproline-rich glycoproteins

Post-Docs Advised (13)

  • Dr. Dominique Rumeau (France)
  • Dr. Adrian Butt (England)
  • Dr. John Crosby (USA)
  • Dr. Jinsong Sheng (USA)
  • Dr. Jim Thomas (USA)
  • Dr. Gabriella Scippa (Italy)
  • Dr. Hua Lu (USA)
  • Dr. Ines Chaves (Portugal)
  • Dr. Wenliang Xu (China)
  • Dr. Wei Tang (China)
  • Dr. Yizhu Zhang (China)
  • Dr. Yan Liang (China)
  • Dr. Melanie Schori (USA)

Funding


Departmental Social Media

College of Arts & Sciences