Molecular and phenotypic characterization of wild-type and Lc transgenic sweet potato.
(A) Classification of sweet potato root developmental stages (S1 to S20). S1-S8, Fibrous roots; S9-S13, Early developmental stage of storage roots; S14-S17, Late developmental stage of storage roots; S17–20, Mature storage roots. The pencil roots cover the size of stages from S9 to S17 but are uniformly thickened and lignified. (B) Southern blot analysis of HindIII-digested genomic DNA using the DIG-labeled hygromycin phosphotranferase gene (hpt) probe. M, Molecular marker; Lc1–5, independent Lc transgenic lines; WT, wild type. (C,D) Comparison of Lc expression levels in the developing storage root (S16), stem and leaf of three 2-month-old Lc transgenic lines by RT-PCR (C) and qRT-PCR analysis. (D) The sweet potato ACTIN gene was used as a reference for normalization and the Lc expression levels in Lc1 tissues was used for calibration in qRT-PCR assay. (E) Phenotypes of the WT and Lc transgenic plants in the field showing the shoots, the 3rd fully expanded leaves from the top, stems and cross-sections of the developing storage roots (S16) after 2 months of growth.