PHYSIOLOGIA PLANTARUM 99: 153-159. 1997 Copyright © Physiologia Plantarum 199 Printed in Denmark - all rights reserved ISSN 0031-9317 Differential accumulation of water stress-related proteins, sucrose synthase and soluble sugars in Populus species that differ in their water stress response Dan Pelah, Wangxia Wang, Arie Altman, Oded Shoseyov and Dorothea Bartels Pelah, D., Wang. W., Altman, A., Shoseyov, O. and Bartels, D. 1997. Differential ac- cumulation of water stress-related proteins, sucrose synthase and soluble sugars in Populus species that differ in their water stress response. - Physiol. Plant. 99: 153- 159. Proteins inducible by dehydration and abscisic acid (ABA), have been identifted in a number of species and have been suggested to play a role in desiccation tolerance. Re- cently, we identified a novel boiling-stable protein (BspA) which accumulated in shoots of aspen (Populus tremula L.) cultured in vitro, in response to gradual water stress and ABA application (Pelah et al. 1995. Tree Physiol. 15: 673-678.). Accumu- lation of BspA, and of the water stress-related protein dehydrin dsp-16 and sucrose synthase from the resurrection plant, Craterostigma plantagineum, was examined in two greenhouse-grown Populus species to investigate the relationship between the presence of the proteins and water stress tolerance. Detached leaves of Populus to- mentosa lost more water than Populus popularis, resulting in a significant decrease in leaf water potential. Using electrolyte leakage analysis, it was found that detached leaves of Populus popularis are more tolerant to water stress than those of Populus to- mentosa. Using western blots with the corresponding antibodies, we have found in Populus popularis accumulation of BspA and sucrose synthase due to water stress, and the constitutive presence of a dehydrin-like protein. In contrast, a low expression of BspA was found in Populus tomentosa, but not of sucrose synthase and dehydrin- like proteins. Desiccation tolerance in many tissues can be partly attributed to soluble sugars. Analysis of the amount of soluble sugars did not reveal clear-cut differences between the two species, except for significant sucrose accumulation and glucose re- duction in water-stressed Populus tomentosa and increase in glucose in water-stressed Populus popularis. The data obtained points to a positive correlation between in- creased water stress tolerance of one poplar species as compared with another and ac- cumulation of water stress-related proteins and sucrose synthase. Key words - BspA, Craterostigma plantagineum, dehydrins, Populus, sucrose syn- thase, water stress. D. Pelah, W. Wang, A. Aliman (corresponding auihor, e-mail aliman@agri.huji.ac. il) and O. Shoseyov, The Kennedy-Leigh Center for Horticultural Research, The Faculty of Agriculture, The Hebrew University of Jerusalem, P. O. Box 12, Rehovot 76100, Is- rael: D. Bartels, Max-Planck Institute, Carl-Von Linne weg 10, D-50829, Koln, Ger- many. molecular changes and tissue response to water stress Introduction j^^y ^j^j ^j^g selection of drought-tolerant species, and Plant growth and productivity is negatively affected by the elucidation of underlying control mechanisms. Water water stress and other environmental stresses, and ge- loss from plant tissues under drought conditions results netic improvement of water stress tolerance is of special in growth inhibition and in a number of other metabolic importance to agricultural plants. Early monitoring of and physiological changes. These include accumulation Received 11 March, 1996; revised 23 September, 1996 153 Physiol. Plant. 99, 1997