Physiologia plantarum vol:125 issue:4 pages:419-429
Inulin- type fructans are stored in the tuberous roots of the Brazilian cerrado plant Viguiera discolor Baker ( Asteraceae). In Cynara scolymus ( artichoke) and Echinops ritro ( globe thistle), the fructans have a considerably higher degree of polymerization ( DP) than in Cichorium intybus ( chicory) and Helianthus tuberosus ( Jerusalem artichoke). It was shown before that the higher DP in some species can be attributed to the properties of their fructan: fructan 1- fructosyl transferases ( 1- FFTs; EC 184.108.40.206), enzymes responsible for chain elongation. Here, we describe the cloning of a high DP ( hDP) 1- FFT cDNA from V. discolor and its heterologous expression in Pichia pastoris. Starting from 1- kestose and Neosugar P ( a mixture of oligo- inulins from microbial origin) as substrates, the recombinant enzyme produces a typical hDP inulin profile in vitro, closely resembling the one observed in vivo. The enzyme shows no invertase activity and sucrose: sucrose 1- fructosyl transferase ( 1- SST; EC 220.127.116.11) activity in vitro. Pattern evolution during incubation suggests that inulins with DP >= 6 are much better substrates than sucrose or lower DP oligo- fructans. Because hDP inulin- type fructans show superior properties for specific food and non- food applications, the hDP 1- FFT gene from V. discolor has potential for the production of hDP inulin in vitro or in transgenic crops.