FRUCTAN SYNTHESIS IN TRANSGENIC TOBACCO AND CHICORY PLANTS EXPRESSINGBARLEY SUCROSE-FRUCTAN 6-FRUCTOSYLTRANSFERASE

We have recently cloned a cDNA encoding sucrose:fructan 6-fructosyltra nsferase (6-SFT), a key enzyme of fructan synthesis forming the beta-2 ,6 linkages typical of the grass fructans, graminans and phleins [Spre nger et al. (1995) Proc. Natl. Acad. Sci. USA 92, 11652-11656]. Here w e report functional expression of 6-SPT from barley in transgenic toba cco and chicory. Transformants of tobacco, a plant naturally unable to form fructans, synthesized the trisaccharide kestose and a series of unbranched fructans of the phlein type (beta-2,6 linkages). Transforma nts of chicory, a plant naturally producing only unbranched fructans o f the inulin type (beta-2,1 linkages), synthesized in addition branche d fructans of the graminan type, particularly the tetrasaccharide bifu rcose which is also a main fructan in barley leaves.