Dr. Thomas Arnold

I am a biochemist who studies the secondary metabolic pathways and bioactive natural products of plants and marine organisms. I’m particularly interested in how plants respond to herbivores and microbial pathogens by producing toxins, deterrents, and airborne / waterborne chemical cues. My lab has studied secondary metabolites which function as herbivore deterrents, antimicrobials, or airborne chemical cues in brown algae, saltmarsh plants, and seagrasses, forest trees and crop plants. Like other members of the department, I aim to conduct high-quality research in the laboratory and in the field with a team of undergraduate students.

I grew up on the Chesapeake Bay and received my B.A. Biology from St. Mary’s College of Maryland and a doctorate at the University of Delaware’s College of Marine Studies. I completed two post-doctoral positions, one at Delaware and another at Penn State, and spent several years at the College of Charleston in South Carolina before coming to Dickinson in 2003. I enjoy SCUBA diving and underwater photography.

I teach Plant Physiology (spring), Metabolism (fall), Changing Ocean Ecosystems(fall / spring), and Chemical Ecology (fall). I am also serving as the chair of the College’s Research and Development Committee and the Institutional Biosafety Committee. Click on the link to see my new research: Tom Arnold

Courses Taught

Changing Ocean Ecosystems (BIOL 129)
Chemical Ecology (BIOL 401)
Plant Physiology (BIOL 325)
Metabolic Disorders (BIOL 122)
Metabolism (BIOL 342)

Educational Background

Postdoctoral Fellow • Pennsylvania State University • 1999-2000
NSF Research Training Grant: Plant responses to the environment.
Focus: Plant biochemistry and secondary metabolism.
Advisor: Jack C. Schultz

Postdoctoral Research Associate • University of Delaware • 1998-9
Focus: Biochemistry of marine organisms, metabolic pathway regulation.
Advisor: Nancy M. Targett

Ph.D. Marine Biology / Biochemistry • University of Delaware • 1998
Focus: Influence of environmental change on the metabolism of algal natural products.
Comprehensive exams in biochemistry, chemical ecology, and plant ecophysiology.
Advisor: Nancy M. Targett

B.A. Biological Sciences • St. Mary’s College of Maryland • 1993
Thesis: Phenotypic variation in the polyphenolic content of the alga Lobophora variegata.
Advisors: Christopher E. Tanner, Walter I. Hatch

Research

In my laboratory, we study the way in which plants respond to attack by insects, fish, and pathogens by using signal transduction pathways to trigger secondary metabolic processes. We are especially interested in the junctions between primary metabolism and secondary metabolism, where resources are made available for the production of toxic or deterrent natural products such as phenolics, alkaloids, and proteinase inhibitors. Together with researchers at other institutions, we have characterized the phenomena whereby plants transport sugars over long distances to support the production of toxins at wound sites (a ‘wound-induced sink strength”). We have shown that this occurs in trees, crop plants, and marine seagrasses and have come to believe that this is a common, first step in plant defense responses. As a result we employ a variety of models systems - including poplar trees and gypsy moth caterpillars, crops plants and their pests, and seagrasses and the wasting disease pathogen Labyrinthul. We are also interested in environmental factors which influence resource availability and the production of these chemical defenses and, as a result, we are interested in changing atmospheric CO2 levels, sea surface temperatures, and eutrophication.

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Two ongoing projects include: (1) a characterization of wound-induced sink strength and the role of cell wall invertase enzymes in plant defense responses and (2) the impact of ocean acidification and other aspects of climate change on the disease resistance of coastal seagrasses. Both of these projects focus on the production of shikimic acid / phenylpropenoid natural products, including condensed tannins in forest trees, resveratrol production in grape, and phenolic acid accumulations in seagrasses. Our approach is to combine biochemical and physiological studies to identify the roles of natural products in plant-pest and plant-pathogen interactions. Currently, we focus on the importance of carbon acquisition and within-plant transport in the synthesis of (poly)phenolics. These projects have been funded by grants from the National Science Foundation. Click on the link to see my new research: Tom Arnold

We have recently developed and field tested the first operational Free-Ocean-Carbon-Enrichment (FOCE) system which mimics the conditions of climate change within seagrass and coral reef ecosystem. This FOCE system is deployed in the Chesapeake Bay.

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Selected Publications (* indicates student co-author)

Steele L*, Caldwell M*, Boettcher A, and Arnold TM (2006) Seagrass-pathogen interactions: “psuedo-induction” of turtlegrass phenolics near wasting disease lesions. Mar. Ecol. Prog. Ser. 303:123-128

Arnold TM, Appel H, Patel V*, Stocum E*, Kavalier A*, and Schultz JC (2004) Carbohydrate translocation determines the phenolic content of Populus foliage: a test of the sink-source model of plant defense. New Phytologist 164(1) 157-164

Arnold TM, Targett NM. (2003) To grow and defend: the primary and secondary roles of brown algal phlorotannins. Oikos 100 (2): 406-408

Arnold TM and Targett NM. (2002) Review: Physiological basis of defense in marine macrophytes. J. Chem. Ecol. 28 (10): 1919-1934

Arnold TM and Schultz, JC. (2002) Induced sink strength as a prerequisite for tannin biosynthesis in Populus. Oecologia 130: 585-593

Arnold TM, Targett NM, Tanner CE, and Hatch WI. (2001) Evidence for methyl jasmonate-induced polyphenolics in Fucus vesiculcosus. J. Phycol. 37:1026-1029

Targett NM and Arnold TM. (2001) Influence of algal secondary metabolites on marine herbivore digestion. Chapter in: Marine Chemical Ecology. 391-412 CRC Press. B. Baker and J. McClintock, Eds.

Arnold TM and Targett NM. (2000) Turnover of polyphenolic chemical defenses in marine brown algae. J. Chem. Ecol. 26(6): 1393-1410

Arnold TM and Targett NM. (1998) Quantifying in situ rates of phlorotannin synthesis in marine brown algae. J. Chem. Ecol. 24(3): 577-595

Targett NM and Arnold TM (1998) Review: The role of algal phlorotannins in marine plant-herbivore interactions. J. Phycol. 34(2): 195-205

Selected Presentations (* indicates student co-author)

Pye M*, Arnold TM, Appel H, and Schultz J (2006) Modulators of plant invertase activities.

Pye M*, Arnold TM, Appel H, and Schultz J (2006) Modulators of plant invertase activities. Department of Biology, 2006 research symposium. Dickinson College.

Boettcher AA, Tanner CE, and Arnold TM (2006) Physiology of seagrasses infected by Labyrinthula pathogens. American Society of Plant Biologists – Southern Section annual meeting, Daytona Beach, FL.

Boettcher AA, Tanner CE, and Arnold TM (2005) Microbial infection of coastal seagrasses: multiple forms of Labyrinthula differ in virulence. Estuarine Research Federation biannual meeting. College of William and Mary, Virginia.

Arnold TM, Boettcher AE, and Tanner CE (2005) The “psuedo-induction” of seagrass phenolics: evidence against an antimicrobial response in plants infected with the wasting disease agent, Labyrinthula sp. International Society of Chemical Ecology annual meeting, Washington, D.C. (invited speaker for special session)

Jillson B* and Arnold TM (2005) PAL activities as biomarkers of eelgrass health in moderate to low light levels. Department of Biology, 2004 research symposium. Dickinson College.

Heath J* and Arnold TM (2005) Behavior of poplar foliage to insect attack: why old leaves are not inducible. Department of Biology, 2004 research symposium. Dickinson College.

Arnold TM, Appel H, Schultz JC. (2004) Carbohydrate translocation determines the phenolic content of Populus foliage: a test of the sink-source model of plant defense. International Society of Chemical Ecology Meeting, Ottawa, Canada.

Dente J* and Arnold TM (2004) Seagrasses at risk? Loss of induced PAL activity on eutrophied waters. Department of Biology, 2004 research symposium. Dickinson College.

Rhode E* and Arnold TM (2004) Caffeic acid production in eelgrass, Zostera marina. Department of Biology, 2004 research symposium. Dickinson College.

Selected Funding Awarded

July, 2006 – July, 2009. National Science Foundation - Ecological and Evolutionary Physiology Program. "A multispecies comparison of induced carbohydrate and secondary metabolism." ($157,187)

Dickinson College R&D. "Vineyard teaching school" Award to support to the development of a small vineyard to serve as a “living classroom”. ($1920)

June-August, 2005. Summer Visiting Scientist Award - Baruch Marine Field Laboratory, University of South Carolina. Biochemistry of induced defenses in the marsh grass, Spartina alterniflora. ($2000)

July, 2004. Dickinson College - Research and Development grant. Page charges and cover photograph for the journal New Phytologist. ($448)

October 1, 2001 – July 30, 2005. National Science Foundation - Biological Oceanography Program. Grant #OCE-0117313. Mechanisms of seagrass disease resistance. ($103,869)

November 1, 2001 – July 30, 2005. National Science Foundation - Ecological and Evolutionary Physiology Program. "Induced sink strength and tannin biosynthesis in Populus." ($95,041)

March 2001-November 2001. Department of Biology, College of Charleston. "Survey of induced sink strength in woody plants. ($648)

1995 & 1996. Sigma Xi - Grants in Aid of Research, combined funding. ($980)