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Trehalose plays a role in drought stress resistance in a variety of organisms, including the extremely drought-tolerant «resurrection plants». Transgenic tobacco plants that produce trehalose were engineered by introduction of the Escherichia coli ots A and ots B genes, encoding trehalose-6-P synthase and trehalose-6-P phosphatase, respectively. The introduction of these genes had a pronounced effect on plant morphology and growth performance under drought stress. The transgenic Ots plants had larger leaves and altered stem growth. When grown under drought stress imposed by limiting water supply, the two transgenic tobacco lines Ots2 and Ots 5 yielded total dry weights that were 28 % and 39 % higher than those of wild-type tobacco. These increases in dry weight were due mainly to increased leaf production: leaf dry weights were up to 85 % higher for the best trehalose accumulator, Ots 5. No significant …