High-level fructooligosaccharide production in transgenic tobacco plants

β-fructofuranosidase (FFase) of Aspergillus niger ATCC 20611 can transfer fructosyl residues from one sucrose to another for the synthesis of glucose and fructooligosaccharides composed of 1-kestose (GF2), nystose (GF3), and β-fructofuranosylnystose (GF4). The FFase gene, under the control of the sporamin gene promoter from sweet potato, was introduced into tobacco plants. Sporamin promoter activity is induced by sugar and exhibits preferential expression in stem and root tissues. Thin-layer and high performance liquid chromatographic analyses showed that soluble extracts from the transgenic plants contained considerable amounts of fructooligosaccharides such as GF2 and GF3. The conversion of sucrose into fructooligosaccharides did not affect plant growth or development. Our results indicate that the transgenic plants could be utilized as bioreactors, and this opens up the possibility for efficient production of fructooligosaccharides in sucrose-producing plants such as sugar beet and sugarcane.