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- Title
Fructan:fructan 1-fructosyltransferase, a key enzyme for biosynthesis of graminan oligomers in hardened wheat.
- Authors
Kawakami, Akira; Yoshida, Midori
- Abstract
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 ß-(2,1)- and ß-(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 ß-(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 ß-(2,1)-linked fructosyl units to phlein, an extension of sucrose through ß-(2,6)-linked fructosyl units, as well as to inulin, an extension of sucrose through ß-(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 ß-(2,1)-linked fructosyl units to phlein and graminan oligomers synthesized by 6-SFT and contributes to accumulation of fructans containing ß-(2,1)- and ß-(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.
- Subjects
WHEAT; FRUCTANS; OLIGOMERS; BIOSYNTHESIS; PLANT cells &; tissues; PLANTS in winter; CATALYSIS; RECOMBINANT proteins
- Publication
Planta: An International Journal of Plant Biology, 2006, Vol 223, Issue 1, p90
- ISSN
0032-0935
- Publication type
Article
- DOI
10.1007/s00425-005-0054-6