Fructan Metabolism in A. tequilana Weber Blue Variety along Its Developmental Cycle in the Field

Abstract

Fructan, as reserve carbohydrate, supplies energy needs during vegetative development, thereby exhibiting variations in its content and composition. Fructan metabolism in Agave tequilana Blue variety from 2- to 7-year-old plants was analyzed in this work. Soluble carbohydrates were determined at all ages. Fructan (328-711 mg/g), sucrose (14-39 mg/g), fructose (11-20 mg/g), glucose (4-14 mg/g), and starch (0.58-4.98 mg/g) were the most abundant carbohydrates. Thin-layer chromatography exhibited that 2-5-year-old plants mainly stored fructooligosaccharides, while 6-7-year-old plants mainly contained long-chain fructans. The fructan degree of polymerization (DP) increased from 6 to 23 throughout plant development. The 7-year-old plants mainly stored highly branched agavins. Partially methylated alditol acetate analyzed by gas chromatography-mass spectrometry reveals that fructan molecular structures became more complex with plant age. For the first time, we report the presence of a large number of DP3 (seven forms), DP4 (eight forms), and DP5 (six forms) isomers for agave fructans. Overall, fructan metabolism in A. tequilana displays changes in its soluble carbohydrates, DP, type, and fructan structures stored, along its developmental cycle in the field.