C

Figure 1. Representative pathways are shown here. Excellent detailed descriptions may be found in this book and other review articles [3, 7, 8], A. In plants, which synthesize fructan, current knowledge suggests that sucrose must first be transported across the tonoplast. Synthesis of a polymer containing up to 60 fructose residues involves the action of at least two separate enzymes (SST and FFT). The enzyme SST acts on sucrose to produce kestose, which is then elongated by FFT. B. The starch biosynthetic pathway in maize endosperm is far more complex. Metabolic intermediates are formed both in the cytosol and in the amyloplast. Free glucose is produced as a result of fructan synthesis, however, fructose is an end-product in the starch synthesis pathway. C. In bacterial species, such as Bacillus amyloliquefaciens, a single enzyme converts sucrose into a polymer containing over one thousand fructose residues.

for such a role due to decades of yield optimization through extensive breeding programs and the established networks of harvest, storage, processing and shipping infrastructures. Maize is, however, a starch-storing species and it is not immediately apparent whether it can be transformed into a fructan-storing crop.

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