Starch metabolic gene expression profile, β-amylase activity and starch status in young mature leaves, storage roots of wild-type and Lc transgenic sweet potato.
(A) Expression levels of the genes involved in starch biosynthesis (AGPa, AGPb, GBSSI, SBEI, SBEII and SS) and starch degradation (α-amylase and β-amylase) in the leaf, stem and developing storage root (S16) of 2-month-old plants. WT, wild type; Lc1–3, independent Lc transgenic lines; AGPa, ADP-glucose pyrophosphorylase alpha subunit; AGPb, ADP-glucose pyrophosphorylase beta subunit; GBSSI, granule-bound starch synthase 1; SBEI, starch branching enzyme I; SBEII, starch branching enzyme II; SS, soluble starch synthase. (B) Starch content and β-amylase activity in response to diurnal rhythms in mature leaves. (C) Starch content in mature storage roots (S20) of field-grown plants and β-amylase activity of developing storage roots (S16). (D) Dark blue starch granules on sections of early developing storage roots (S12) of 2-month-old plants as determined using Lugol’s solution and TEM observation. Error bars represent the SE of three independent replicates. The asterisks indicate a significant difference compared to the WT at *P < 0.05 or **P < 0.01 (t-test).