Research Interests:

My current research focuses on how plant cells regulate calcium. To do this I use plants that sequester calcium in the form of calcium oxalate crystals. Since these plants process large quantities of calcium, they make ideal models for studying how plant cells control calcium levels within cells and tissues. Cytosolic calcium at above micromolar levels is toxic to plants, as calcium is used as a signaling molecule and excesses of calcium therefore disrupt cell metabolism. The first step in approaching these problems is to understand the biology and biochemistry of the cells that sequester calcium. These are specialized cells called crystal idioblasts. I am looking at a variety of crystal producing plants to understand crystal idioblast cell biology and to gain a full understanding of the calcium buffering system in different plant families. Current species I am studying include Pistia stratiotes (waterlettuce), Lemna minor (duckweed), Eichornia crassiopes (water hyacinth), Peperomia obtusifolia, Peperomia caperata, and Medicago sativum (alfalfa).

My other interest is in the other component of calcium oxalate crystals, the oxalic acid and how it is biosynthesized. Plants that produce large quantities of oxalic acid are considered toxic and pose threats to humans and livestock consuming them. I am pursuing funding to look the biosynthesis of oxalate in high oxalate accumulating species. There is some evidence that the main precursor of oxalic acid is L-ascorbic acid, or vitamin C. If this is shown to be true, our increasing knowledge of the biosynthesis of vitamin C could lead to methods of controlling oxalic acid production in poisonous species.

Publications:

Tarlyn, N.M, Kostman, T.A., Nakata, P.A., Keates, S.E., and Franceschi, V.R. 1998. Axenic culture of Pistia stratiotes for use in plant biochemical studies. Aquatic Bot. 60: 161-168.

Kostman, T.A. and Franceschi, V.R. 2000. Cell and calcium oxalate crystal growth is coordinated to achieve high capacity calcium regulation in plants. Protoplasma 214 (3-4):166-179.

Quitadamo, I.J., Kostman, T.A, Schelling, M.E., and Franceschi, V.R. 2000. Magnetic bead purification as a rapid and efficient method for enhanced antibody specificity for plant sample immunoblotting and immunolocalization. Plant Science 153: 7-14.

Kostman, T.A., Tarlyn, N.M., Franceschi, V.R. and Loewus, F.A. 2001. Biosynthesis of L-ascorbic acid and conversion of carbons 1 and 2 of L-ascorbic acid to oxalic acid occurs within individual calcium oxalate crystal idioblasts. Plant Phys. 125(2): 1-7.

Volk, G.M., Lynch-Holm, V.J., Kostman, T.A., Goss, L.J., and Franceschi, V.R. 2002. The role of druse and raphide calcium oxalate crystals in tissue calcium regulation in Pistia stratiotes leaves. Plant Biology 4: 34-45.

Kostman, T.A., and Koscher, J.R. L-galactono-g-lactone-dehydrogenase is present in calcium oxalate crystal idioblasts of two plant species. In review, Plant Physiology and Biochemistry.

Kostman, T.A., Franceschi, V.R, and Nakata, P.A. Specialized ER sub-domains may play a role in calcium regulation in crystal idioblasts of Pistia stratiotes. In review, Protoplasma.