The vacuolar sorting domain of sporamin transports GUS, but not levansucrase, to the plant vacuole

• Published in: New phytologist Vol. 136; no. 1; pp. 29 - 38
• Main Authors: TURK, STEFAN C. H. J., DE ROOS, KOEN, SCOTTI, PIER A., VAN DUN, KEES, WEISBEEK, PETER, SMEEKENS, SJEF C. M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford, UK Cambridge University Press 01.05.1997; Blackwell Publishing Ltd; Blackwell
• Subjects: Biological and medical sciences; Enzymes; Fructans; Fundamental and applied biological sciences. Psychology; GUS; Leaves; levansucrase; Metabolism; Photosynthesis, respiration. Anabolism, catabolism; Plant cells; Plant physiology and development; Plants; Plasmids; Proteins; Protoplasts; sporamin; Starches; Vacuolar protein sorting; Vacuoles; levansucrase; Vacuolar protein sorting; fructans; GUS; sporamin; Enzyme; Bacillus subtilis; Levansucrase; Transferases; Chain length; Glycosyltransferases; Polymer; Biosynthesis; Bacillaceae; Gene expression; Nicotiana tabacum; Vacuole; Bacillales; Dicotyledones; Angiospermae; Fructosan; Bacteria; Hexosyltransferases; Spermatophyta; Carbohydrate; Transgenic plant; Solanaceae; Biological accumulation; Localization
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.1997.tb04728.x

Fructans (polyfructosylsucrose) are synthesized by a number of plants and micro-organisms. Plant fructans are localized in the vacuole and have a low degree of polymerization (DP), whereas the fructans synthesized by micro-organisms are usually much bigger. There is an increasing interest in fructans for both food and non-food applications. In order to accumulate fructans of high DP in the plant vacuole, the levansucrase protein of Bacillus subtilis was fused to the vacuolar targeting sequence of sporamin and expressed in plants. Transgenic tobacco plants in which this fusion gene is expressed accumulate fructans to levels up to 21% of the d. wt. They showed a reduced translocation of carbohydrates, bleaching of the leaves, stunted growth and increased levels of hexoses and starch. The levansucrase protein was not translocated to the plant vacuole, but retained in the endomembrane system, even though the same targeting signal was able to translocate the E. coli GUS protein to the plant vacuole.