B.S., Biology, City College of New York
Ph.D., Plant Pathology, Rutgers University

A major thrust of our program is to understand the mechanism whereby ozone induces accelerated foliar senescence. Normal senescence follows a carefully timed program in which some genes, known as senescence associated genes, are"turned on" while other genes are"turned off." We are conducting experiments to determine which of these genetic responses are induced by ozone. Ethylene, a hormone associated with senescence, is induced by ozone. The enzyme, 1-aminocyclopropane-1-carboxylate (ACC) synthase, regulates the biosynthesis of ethylene. Several members of the multigene family which encode ACC synthase are induced by ozone. We have identified several of these genes and are currently transforming potato plants with the antisense for two of these ACC synthase genes. We will be conducting experiments to determine whether these transgenic plants have reduced capacity to respond to ozone.

Earlier we determined that ozone induces a loss of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). By studying the structure of the protein and its response to ozone-induced oxidation, we have learned that ozone increases the rate of degradation of Rubisco in older leaf tissue. Interestingly, in younger foliage of ozone-treated plants, the rate of Rubisco biosynthesis actually exceeds that of companion plants in a charcoal-filtered environment. We are exploring the compensatory potential that this response may offer the plant, and the importance of available nitrogen to the induction of the response. In addition, we are investigating the potential signals that ozone-stressed senescing leaves might be sending to the younger leaves to induce this compensatory response.

The first line of defense to a plant exposed to ozone is the stomate. Guard cells close in response to the air pollutant, but the sensitivity of the guard cells varies with species, environmental conditions and exposure dynamics. In collaboration with Dr. Sarah Assmann in the biology department, we are exploring the mechanism by which ozone affects guard cells. Through patch clamping experiments we are studying the electrophysiological response of membranes of guard cells to ozone.

Wiese, C. B. and Pell, E. J. 1997. "Influence of ozone on transgenic tobacco plants expressing reduced quantities of Rubisco." Plant, Cell and Environment 20:1283-1291

Schlagnhaufer, C. D., Arteca, R. N. and Pell, E. J. 1997. "Sequential expression of two 1-aminocyclopropane-1-carboxylate synthase genes in response to biotic and abiotic stresses in potato (Solanum tuberosum L.) leaves." Plant Molecular Biology 35:683-688.

Brendley, B. and Pell, E. J. 1998 "Ozone-induced changes in biosynthesis of Rubisco and associated compensation to stress in foliage of hybrid poplar." Tree Physiology 18:81-90.

Pell, W. J., Sinn, J. P., Brendley, B. E., Samuelson, L., Vinten-Johansen, C., Tien, M. and Skillman, J. 1999. "Differential response of four tree species to ozone-induced acceleration of foliar senescence." Plant, Cell and Environment 22:779-790.

Miller, J. D., Arteca, R. N. and Pell, E. J. 1999. "Senescence-associated gene expression during ozone-induced senescence." Plant Physiology 120:1015-1023.

Torsethaugen, G. Pell, E. J. and Assmann, S. M. 1999. "Ozone inhibits guard cell K+ channels implicated in stomatal opening." Proc. Natl Acad. Sci. 96:13577-13582.