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Morphological and Physiological Characterization of Transgenic Tomato Lines Expressing Inositol Polyphosphate 5-phosphatase.  Courtney Sword¹, Mariya Khodakovskaya¹, Imara Y. Perera¹, Christopher S.Brown^{1, 2}, Heike Winter- Sederoff ^{1 1}Department of Plant Biology, and ²Kenan Institute for Science, Technology, and Engineering, North Carolina State University, Raleigh, NC

   Plants are adapted to the physical conditions they encounter on earth in their specific environment. Most of the environmental factors such as temperature, water availability, light, atmospheric pressure, and radiation will be dramatically different in space and on other planets. The only possible approach to increase the tolerance of crop plants to multiple and extreme environmental condition is genetic engineering. It has been shown that inositol-1,4,5-trisphosphate (InsP₃) is involved in several signal transduction pathways.  Plant responses to salt, drought, cold, and osmotic stresses as well as tropic responses to light and gravity are mediated by inositolphosphate metabolism (Meijer and Munnik, 2003, Perera et al. 2006 and unpublished data). We generated transgenic tomato plants expressing the human inositol polyphosphate 5-phosphatase (InsP₃ 5-ptase), an enzyme that hydrolyzes InsP_3. These plants have an enhanced tolerance to drought stress (Khodakovskaya et. al. 2006, unpublished data). To understand the mechanisms involved in stress tolerance of these transgenic tomato plants we characterized morphological and physiological parameters of independent homozygeous transgenic lines in comparison with wild type and vector control lines. The average leaf thickness was significantly increased in the transgenic lines and the diameter of the main stems increased. Even though their tolerance to drought stress dramatically increased, no significant physiological differences were observed between wild type and transgenic tomato lines in stomatal conductance, electron transport rate, and maximum quantum yield. We are presenting data of detailed morphological characterization and discussing possible mechanisms of the basis of those observed morphological changes in the genetically modified lines.    

(Project supported by NASA grant NAG2-1566 to Christopher S. Brown and North Carolina State Grant Consortium grant 526294 to Mariya Khodakovskaya)