Thomas D. Sharkey

Last updated
Thomas "Tom" D. Sharkey
AwardsUniversity Distinguished Professor
Fellow of the American Association for the Advancement of Science
Fellow of American Society of Plant Biologists
Scientific career
Institutions Michigan State University
Australian National University
University of Wisconsin-Madison
Thesis Stomatal Responses to Light in Xanthium strumarium and other species
Doctoral advisor Klaus Raschke
Website bmb.natsci.msu.edu/faculty/thomas-d-sharkey/

Thomas D. Sharkey is a plant biochemist who studies gas exchange between plants and the atmosphere. His research has covered (1) carbon metabolism of photosynthesis from carbon dioxide uptake to carbon export from the Calvin-Benson Cycle, (2) isoprene emission from plants, and (3) abiotic stress tolerance. Four guiding questions are: (1) how leaf photosynthesis affects plant yield, (2) does some carbon fixation follow an oxidative pathway that reduces sugar output but stabilizes photosynthesis, (3) why plants make isoprene, and (4) how plants cope with high temperature.

Contents

Education and Training

Tom Sharkey obtained a BS degree in 1974 from Lyman Briggs College, a residential college within Michigan State University (MSU) focusing on the study of natural science and the history and philosophy of science. He obtained his PhD in 1980 from the Department of Botany and Plant Pathology (now Plant Biology) at MSU for research conducted in the MSU-DOE Plant Research Laboratory. His thesis work was carried out under the direction of Professor Klaus Raschke and was titled Stomatal Responses to Light in Xanthium strumarium and Other Species.

Professional Experience

After 2.5 years as a Post-doctoral Fellow in the Department of Environmental Biology at the Australian National University under the supervision of Professor Graham Farquhar, Sharkey spent five years (1982-1987) at the Desert Research Institute in Reno, Nevada. There he carried out experiments with the noted plant physiologist Professor Frits Went. He then went to the University of Wisconsin-Madison for 20 years where he held various administrative posts such as Chair of the Department of Botany, Director of the UW-Madison Biotron, and Director of the Institute for Cross College Biology Education. In 2008 Sharkey was recruited back to Michigan State University to become Chair of the Department of Biochemistry and Molecular Biology. In 2015 he was named a University Distinguished Professor.

Sharkey has been Series Editor for the book series Advances in Photosynthesis and Respiration and Senior Editor for the journal Plant, Cell & Environment. He was elected Fellow of the American Society of Plant Biologists in 2007 and Fellow of the American Association for the Advancement of Science in 2011.

Research

Sharkey studies the biochemistry and biophysics that underlie plant-atmosphere interactions especially photosynthesis and isoprene emission from plants. Significant accomplishments related to photosynthesis include the measurement of carbon dioxide concentration inside leaves, [1] measurement of the biophysical resistance to carbon dioxide diffusion within leaves, [2] [3] [4] [5] elucidation of the biochemical feedback chain that explains how limitations in starch and sucrose synthesis reduce the efficiency of photosynthesis [6] and demonstration that maltose is the primary metabolite exported from chloroplasts at night. [7] [8]

Significant accomplishments related to isoprene biosynthesis and emissions from plants include the first genomic sequence of an isoprene synthase, [9] cloning isoprene synthases from ten different plant species, [10] analysis of the evolution of isoprene synthases and enzymes needed to make the precursor to isoprene.

Heat stress was shown to be ameliorated by cyclic electron flow in photosynthesis. [11]

Related Research Articles

<span class="mw-page-title-main">Photosynthesis</span> Biological process to convert light into chemical energy

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek phōs, "light", and synthesis, "putting together". Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth.

Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. It is produced by many plants and animals (including humans) and its polymers are the main component of natural rubber. C. G. Williams named the compound in 1860 after obtaining it from the pyrolysis of natural rubber; he correctly deduced the empirical formula C5H8.

<span class="mw-page-title-main">Terpene</span> Class of oily organic compounds found in plants

Terpenes are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes are further classified by the number of carbons: monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), as examples. The terpene alpha-pinene, is a major component of the common solvent, turpentine.

<span class="mw-page-title-main">Jean Senebier</span> Genevan Calvinist pastor and naturalist (1742-1809)

Jean Senebier was a Genevan Calvinist pastor and naturalist. He was chief librarian of the Republic of Geneva. A pioneer in the field of photosynthesis research, he provided extensive evidence that plants consume carbon dioxide and produced oxygen. He also showed a link between the amount of carbon dioxide available and the amount of oxygen produced and determined that photosynthesis took place at the parenchyma, the green fleshy part of the leaf.

<span class="mw-page-title-main">Crassulacean acid metabolism</span> Metabolic process

Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but they open at night to collect carbon dioxide and allow it to diffuse into the mesophyll cells. The CO2 is stored as four-carbon malic acid in vacuoles at night, and then in the daytime, the malate is transported to chloroplasts where it is converted back to CO2, which is then used during photosynthesis. The pre-collected CO2 is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency. This mechanism of acid metabolism was first discovered in plants of the family Crassulaceae.

C<sub>4</sub> carbon fixation Photosynthetic process in some plants

C4 carbon fixation or the Hatch–Slack pathway is one of three known photosynthetic processes of carbon fixation in plants. It owes the names to the 1960's discovery by Marshall Davidson Hatch and Charles Roger Slack that some plants, when supplied with 14CO2, incorporate the 14C label into four-carbon molecules first.

<span class="mw-page-title-main">Photorespiration</span>

Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The desired reaction is the addition of carbon dioxide to RuBP (carboxylation), a key step in the Calvin–Benson cycle, but approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (oxygenation), creating a product that cannot be used within the Calvin–Benson cycle. This process lowers the efficiency of photosynthesis, potentially lowering photosynthetic output by 25% in C3 plants. Photorespiration involves a complex network of enzyme reactions that exchange metabolites between chloroplasts, leaf peroxisomes and mitochondria.

<span class="mw-page-title-main">Ribulose 1,5-bisphosphate</span> Chemical compound

Ribulose 1,5-bisphosphate (RuBP) is an organic substance that is involved in photosynthesis, notably as the principal CO2 acceptor in plants. It is a colourless anion, a double phosphate ester of the ketopentose called ribulose. Salts of RuBP can be isolated, but its crucial biological function happens in solution. RuBP occurs not only in plants but in all domains of life, including Archaea, Bacteria, and Eukarya.

C<sub>3</sub> carbon fixation Most common pathway in photosynthesis

C3 carbon fixation is the most common of three metabolic pathways for carbon fixation in photosynthesis, along with C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into two molecules of 3-phosphoglycerate through the following reaction:

<span class="mw-page-title-main">Phosphoenolpyruvate carboxylase</span> Class of enzymes

Phosphoenolpyruvate carboxylase (also known as PEP carboxylase, PEPCase, or PEPC; EC 4.1.1.31, PDB ID: 3ZGE) is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO3−) to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate and inorganic phosphate:

Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP<sup>+</sup>) Enzyme

Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1.1.1.40) or NADP-malic enzyme (NADP-ME) is an enzyme that catalyzes the chemical reaction in the presence of a bivalent metal ion:

The enzyme isoprene synthase catalyzes the chemical reaction

<span class="mw-page-title-main">Sucrose-phosphate synthase</span>

Sucrose-phosphate synthase (SPS) is a plant enzyme involved in sucrose biosynthesis. Specifically, this enzyme catalyzes the transfer of a hexosyl group from uridine diphosphate glucose (UDP-glucose) to D-fructose 6-phosphate to form UDP and D-sucrose-6-phosphate. This reversible step acts as the key regulatory control point in sucrose biosynthesis, and is an excellent example of various key enzyme regulation strategies such as allosteric control and reversible phosphorylation.

<span class="mw-page-title-main">Absinthin</span> Chemical compound

Absinthin is a naturally produced triterpene lactone from the plant Artemisia absinthium (Wormwood). It constitutes one of the most bitter chemical agents responsible for absinthe's distinct taste. The compound shows biological activity and has shown promise as an anti-inflammatory agent, and should not to be confused with thujone, a neurotoxin also found in Artemisia absinthium.

<span class="mw-page-title-main">Photosynthesis system</span>

Photosynthesis systems are electronic scientific instruments designed for non-destructive measurement of photosynthetic rates in the field. Photosynthesis systems are commonly used in agronomic and environmental research, as well as studies of the global carbon cycle.

(3S,6E)-nerolidol synthase (EC 4.2.3.48, (E)-nerolidol synthase, nerolidol synthase, (3S)-(E)-nerolidol synthase, FaNES1) is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate diphosphate-lyase ((3S,6E)-nerolidol-forming). This enzyme catalyses the following chemical reaction

α-Longipinene synthase is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate diphosphate-lyase (α-longipinene-forming). This enzyme catalyses the following chemical reaction

(E)-β-Ocimene synthase (EC 4.2.3.106, β-ocimene synthase, AtTPS03, ama0a23, LjEbetaOS, MtEBOS) is an enzyme with systematic name geranyl-diphosphate diphosphate-lyase ((E)-β-ocimene-forming). This enzyme catalyses the following chemical reaction

The MSU-DOE Plant Research Laboratory (PRL), commonly referred to as Plant Research Lab, is a research institute funded to a large extent by the U.S. Department of Energy Office of Science and located at Michigan State University (MSU) in East Lansing, Michigan. The Plant Research Lab was founded in 1965, and it currently includes twelve laboratories that conduct collaborative basic research into the biology of diverse photosynthetic organisms, including plants, bacteria, and algae, in addition to developing new technologies towards addressing energy and food challenges.

Chemical defenses in <i>Cannabis</i>

Cannabis (/ˈkænəbɪs/) is commonly known as marijuana or hemp and has two known strains: Cannabis sativa and Cannabis indica, both of which produce chemicals to deter herbivory. The chemical composition includes specialized terpenes and cannabinoids, mainly tetrahydrocannabinol (THC), and cannabidiol (CBD). These substances play a role in defending the plant from pathogens including insects, fungi, viruses and bacteria. THC and CBD are stored mostly in the trichomes of the plant, and can cause psychological and physical impairment in the user, via the endocannabinoid system and unique receptors. THC increases dopamine levels in the brain, which attributes to the euphoric and relaxed feelings cannabis provides. As THC is a secondary metabolite, it poses no known effects towards plant development, growth, and reproduction. However, some studies show secondary metabolites such as cannabinoids, flavonoids, and terpenes are used as defense mechanisms against biotic and abiotic environmental stressors.

References

  1. ↑ Sharkey, TD.; et al. (1982). "A direct confirmation of the standard method of estimating intercellular partial pressure of CO2". Plant Physiology. 69 (3): 657–659. doi:10.1104/pp.69.3.657. PMC   426273 . PMID   16662268.
  2. ↑ Sharkey, TD. (2012). "Mesophyll conductance: Constraint on carbon acquisition by C3 plants". Plant, Cell & Environment. 35 (11): 1881–1883. doi: 10.1111/pce.12012 . PMID   23043351.
  3. ↑ Harley, PC.; et al. (1992). "Theoretical considerations when estimating the mesophyll conductance to CO2 flux by analysis of the response of photosynthesis to CO2". Plant Physiology. 98 (4): 1429–1436. doi:10.1104/pp.98.4.1429. PMC   1080368 . PMID   16668811.
  4. ↑ Loreto, F.; et al. (1992). "Estimation of mesophyll conductance to CO2 flux by three different methods". Plant Physiology. 98 (4): 1437–1443. doi:10.1104/pp.98.4.1437. PMC   1080369 . PMID   16668812.
  5. ↑ Evans, JR; et al. (1986). "Carbon isotope discrimination measured concurrently with gas exchange to investigate CO2 diffusion in leaves of higher plants". Functional Plant Biology. 13 (2): 281–292. doi:10.1071/pp9860281.
  6. ↑ Yang, J.; et al. (2016). "Triose phosphate use limitation of photosynthesis: short-term and long-term effects". Planta. 243 (3): 687–698. doi:10.1007/s00425-015-2436-8. PMID   26620947. S2CID   1450506.
  7. ↑ Weise, SE.; et al. (2005). "β-maltose is the metabolically active anomer of maltose during transitory starch degradation". Plant Physiology. 137 (2): 756–761. doi:10.1104/pp.104.055996. PMC   1065375 . PMID   15665241.
  8. ↑ Weise, SE.; Weber, A.; Sharkey, TD. (2004). "Maltose is the major form of carbon exported from the chloroplast at night". Planta. 218 (3): 474–482. doi:10.1007/s00425-003-1128-y. PMID   14566561. S2CID   21921851.
  9. ↑ Sharkey, TD.; et al. (2005). "Evolution of the isoprene biosynthetic pathway in kudzu". Plant Physiology. 137 (2): 700–712. doi: 10.1104/pp.104.054445 . PMC   1065370 . PMID   15653811.
  10. ↑ Sharkey, TD; et al. (2013). "Isoprene synthase genes form a monophyletic clade of acyclic terpene synthases in the Tps-b terpene synthase family". Evolution. 67 (4): 1026–1040. doi: 10.1111/evo.12013 . PMID   23550753. S2CID   29434246.
  11. ↑ Zhang, R; Sharkey, TD. (2009). "Photosynthetic electron transport and proton flux under moderate heat stress". Photosynthesis Research. 100 (1): 29–43. doi:10.1007/s11120-009-9420-8. PMID   19343531. S2CID   11956742.
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