The N-terminal region of SS4 confers the discoid shape of starch granules. Left panels show light micrographs (LM) of toluidine blue-stained, semithin sections cut from fixed, embedded tissue from leaf number 7 of each line. Middle panels show TEM of ultrathin sections cut from the same samples. Right panels show scanning electron micrographs of starch granules extracted from whole rosettes of the given lines. The lines presented here are those showing the highest expression of the introduced construct, except for YFP-GS, where the line with lowest expression was chosen due to its relatively strong expression. Data from the remaining lines is presented in Supplemental Figures S2 to S4. White bars = 10 µm; black bars = 2 μm. Black arrow, lenticular starch granule; red arrow, spherical starch granule.