INHIBITION OF TREHALASE ACTIVITY ENHANCES TREHALOSE ACCUMULATION IN TRANSGENIC PLANTS

As a first step toward the exploitation of the disaccharide trehalose as a stress-protective and preservative agent in plants, we engineered trehalose biosynthesis in tobacco (Nicotiana tabacum) and potato (Sol anum tuberosum) by introducing the otsA and otsB genes from Escherichi a coli, which encode trehalose-6-phosphate synthase and trehalose-6-ph osphate phosphatase, respectively. In leaves of transgenic tobacco pla nts, very low levels of trehalose accumulation were obtained (0.11 mg g(-1) fresh weight), whereas in transgenic potato tubers, no trehalose accumulated at all. Plant trehalase activity was shown to affect the accumulation of trehalose in these plants. An increase in trehalose ac cumulation, up to 0.41 and 4.04 mg g(-1) fresh weight in tobacco leave s and potato microtubers, respectively, was noted when the potent treh alase inhibitor validamycin A was added to in vitro plants and to hydr oponically grown greenhouse plants. Stunted growth and the formation o f lancet-shaped leaves by trehalose-accumulating tobacco plants sugges t a negative effect of trehalose biosynthesis on N. tabacum developmen t. It is surprising that experiments with wild-type plants cultured in the presence of validamycin A indicate that, despite current belief, the capacity to synthesize trehalose may not be restricted to primitiv e phyla of vascular plants and certain ''resurrection plants,'' but ma y exist throughout the angiosperms.