Fructan:fructan 1-fructosyltransferase, a key enzyme for biosynthesis of graminan oligomers in hardened wheat

• Published in: Planta Vol. 223; no. 1; pp. 90 - 104
• Main Authors: Kawakami, A, Yoshida, M
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.12.2005; Springer; Springer Nature B.V
• Subjects: Amino Acid Sequence; amino acid sequences; Biological and medical sciences; Biosynthesis; Carbohydrate Conformation; Carbohydrate Metabolism; Chromatography, Ion Exchange; Cloning, Molecular; Cold Climate; Cold hardening; cold stress; Complementary DNA; enzyme activity; Enzymes; Flowering; fructan-fructan fructosyltransferase; Fructans; Fructans - biosynthesis; Fructans - chemistry; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Library; graminan; hexosyltransferases; Hexosyltransferases - chemistry; Hexosyltransferases - metabolism; messenger RNA; Metabolism; Molecular Sequence Data; Oligomers; Pichia - genetics; Plant physiology and development; plant response; plant stress; Plants; recombinant fusion proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Recombinant proteins; RNA, Messenger - metabolism; Seasons; Sequence Alignment; Solubility; Sucrose; Transfection; Triticum - chemistry; Triticum - enzymology; Triticum - genetics; Triticum aestivum; Wheat; winter wheat; Monocotyledones; Winter wheat Cold hardening; Cold; Snow; Biosynthesis; Graminan biosynthesis; Survival; Stress; Gramineae; Angiospermae; Fructosan; Spermatophyta; Fructan; Fructan:fructan 1- fructosyltransferase; Triticum aestivum
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-005-0054-6

Fructans play important roles not only as a carbon source for survival under persistent snow cover but also as agents that protect against various stresses in overwintering plants. Complex fructans having both beta-(2,1)- and beta-(2,6)-linked fructosyl units accumulate in wheat (Triticum aestivum L.) during cold hardening. We detected fructan: fructan 1-fructosyltransferase (1-FFT; EC 2.4.1.100) activity for catalyzing the formation and extension of beta-(2,1)-linked fructans in hardened wheat tissues, cloned cDNAs (wft3 and wft4) of 1-FFT, and analyzed the enzymatic properties of a wft3 recombinant protein (Wft3m) produced by yeast. Wft3m transferred beta-(2,1)-linked fructosyl units to phlein, an extension of sucrose through beta-(2,6)-linked fructosyl units, as well as to inulin, an extension of sucrose through beta-(2,1)-linked fructosyl units, but could not efficiently synthesize long inulin oligomers. Incubation of a mixture of Wft3m and another recombinant protein of wheat, sucrose:fructan 6-fructosyltransferase (6-SFT), with sucrose and 1-kestotriose produced fructans similar to those that accumulated in hardened wheat tissues. The results demonstrate that 1-FFT produces branches of beta-(2,1)-linked fructosyl units to phlein and graminan oligomers synthesized by 6-SFT and contributes to accumulation of fructans containing beta-(2,1)- and beta-(2,6)-linked fructosyl units. In combination with sucrose:sucrose 1-fructosyltransferase (1-SST; EC 2.4.1.99) and 6-SFT, 1-FFT is necessary for fructan synthesis in hardened wheat.