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

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 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.

Roles of osmoprotectants in improving salinity and drought tolerance in plants: a review

“…The b-2,6-linked fructan is synthesized via successive coaction of sucrose:sucrose 1-fructosyltransferase (1-SST) and sucrose:fructan 6-fructosyltransferase (6-SFT) (Livingston et al, 2009). The enzyme responsible for synthesis of the b-2,1-linked branch in graminan is fructan:fructan 1-fructosyltransferase (1-FFT) (Kawakami and Yoshida 2005;Garcia et al 2011). In most of the cases, sucrose biosynthesis is regulated by the interconversion of fructose-6-phosphate and fructose-1,6-bisphosphate, and this phenomenon is totally based on three distinct enzymes activities viz.…”

Research on Fructan in Wheat and Temperate Forage Grasses in Japan

“…The degree of polymerization (DP) of wheat fructan is around 3 to 20. Kawakami and Yoshida 8,9 cloned 4 cDNAs that cover all kinds of fructan synthetic enzymes in wheat. Several clones of wheat fructan exohydrolases, 1-FEH 22,25 , 6-FEH (6-KEH) 23,24 , and 6&1-FEH 10 , have been isolated and functionally analyzed.…”

The barley lipid transfer protein, BLT101, enhances cold tolerance in wheat under cold stress

“…Overwintering crops develop cold hardiness after being exposed to low temperatures (LT) (Levitt 1972;Kawakami and Yoshida 2005). The plasma membrane in plants plays a major role in protecting them from cold/freezing.…”

“…Overwintering crops are able to achieve cold acclimation by developing a high level of hardiness, after being exposed to low temperatures (Levitt 1972;Kawakami and Yoshida 2005). This kind of acquired freezing tolerance is accompanied by structural, physiological and biochemical alterations in the plants; the biochemical changes include the accumulation of osmoprotectants, such as sugars (Wanner and Junttila 1999), proline (Dörffling et al 1993), glycine betaine (Allard et al 1998), as well as protective proteins such as LEA (late embryogenesis abundant) proteins, and antifreeze proteins (Yu and Griffith 1999).…”