Thomas D. Sharkey

Research Interests

Research in the Sharkey lab focuses on three main areas centered on the biochemistry and biophysics of gas exchange reactions between plants and the atmosphere. Photosynthetic carbon fixation from carbon dioxide uptake through to synthesis of sucrose and starch is one major area of research. Recent progress includes demonstration that starch breakdown in leaves results in the formation of b-maltose and this is the predominant form of carbon exported from chloroplasts at night.

A second major research focus area is biochemical analysis of isoprene emission from plants. Isoprene is made by the methyl erythritol 4-phosphate (MEP) pathway that is unique to bacteria and plastids of plants. Plants make isoprene to help them cope with rapid increases in temperature that can occur in sunlight (see the figure). The effects of temperature and development on the expression of all of the genes in the MEP pathway, plus isoprene synthase, have been examined. Several of the genes exhibit circadian regulation, although the protein amounts for these enzymes do not vary over the course of a day.

Since isoprene emission appears related to heat tolerance, we initiated a third focus area, studies of heat tolerance mechanisms of photosynthesis. We have found that the energy gradient for making ATP dissipates faster after turning off the light when leaves are at high temperature. This could indicate that heat causes thylakoid membranes to become leaky. We hope to determine if isoprene can counteract this leakiness.

Recent Publications

Eaton-Rye, J.J., B.C. Tripathy, and T.D. Sharkey, eds. Photosynthesis: Plastid Biology, Energy Conversion and Carbon Assimilation, Vol 34 of Advances in Photosynthesis and Respiration, Govindjee and T.D. Sharkey Series eds. Springer Academic Publications, Dordrecht, 2011.

Sharkey,T.D. S.E. Weise. 2011. Autotrophic carbon dioxide fixation. In Photosynthesis: Plastid Biology, Energy Conversion and Carbon Assimilation, J.J. Eaton-Rye, B.C.Tripathy, and T.D. Sharkey (Editors) Vol 34 of Advances in Photosynthesis and Respiration, Govindjee and T.D. Sharkey Series eds. Springer Academic Publications, Dordrecht, pp 649-672.

Velikova VZ, Varkonyi Z, Szabo M, Maslenkova L, Nogues I, Kovacs L, Peeva V, Busheva M, Garab G, Sharkey TD, Loreto F. (2011) Increased thermostability of thylakoid membranes in isoprene-emitting leaves probed with three biophysical techniques. Plant Physiology 157:905-916. Link to article

Zhang R, Kramer DM, Cruz JA, Struck KR, Sharkey TD. (2011) The effects of moderately high temperature on zeaxanthin accumulation and decay. Photosynthesis Research. 108:171-181. Link to article

Gray DW, Breneman SR, Topper LA, Sharkey TD.(2011) Biochemical Characterization and Homology Modeling of Methylbutenol Synthase and Implications for Understanding Hemiterpene Synthase Evolution in Plants. J. Biol. Chem. 286(23) 20582-20590. Link to article

Weise SE, van Wijk KJ, Sharkey TD. (2011) The role of transitory starch in C-3, CAM, and C-4 metabolism and opportunities for engineering leaf starch accumulation. J. Exp. Bot. 62: 3109-3118. Link to article

Li Z, Ratliff EA, Sharkey TD. (2011) Effect of temperature on postillumination isoprene emission in oak and poplar. Plant Physiol. 155(2):1037-46. Link to article

Zhang R, Wise RR, Struck KR, Sharkey TD. (2010) Moderate heat stress of Arabidopsis thaliana leaves causes chloroplast swelling and plastoglobule formation. Photosynthesis Research. Aug;105:123-134. Link to article

Sharkey TD, Zhang R. (2010) High Temperature Effects on Electron and Proton Circuits of Photosynthesis. Journal of Integrative Plant Biology. Aug;52:712-722. Link to article

Darbah JNT, Sharkey TD, Calfapietra C, Karnosky DF. (2010) Differential response of aspen and birch trees to heat stress under elevated carbon dioxide. Environmental Pollution Apr;58:1008-1014. Link to article

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