Extended Data Figure 6: Cellular and subcellular localization of AtSWEET9 and starch accumulation in Atsweet9 mutants.
From: Nectar secretion requires sucrose phosphate synthases and the sugar transporter SWEET9
a–f, Histochemical GUS analysis in Arabidopsis flowers expressing translational GUS fusion of AtSWEET9 (native promoter). a, b, GUS staining in lateral (a) and median (b) nectaries. c–f, Transverse (c, d) and vertical (e, f) sections of Arabidopsis flowers showing tissue-specific localization of AtSWEET9. a, b, Original magnification, ×10. Cell walls stained with safranin-O (orange). GUS activity was highest in the lower (basal) half of the nectary parenchyma, less in the top part of the parenchyma and weak or absent from epidermis and guard cells. g–i, Arabidopsis plants expressing translational AtSWEET9–eGFP fusions under control of its native promoter: lateral nectaries in an immature flower at floral stage 12–13 (unopened flower) (g), lateral nectaries in a mature flower at floral stage 14–15 (open flower) (h) and median nectaries in a mature flower at floral stage 14–15 (i). Auto-fluorescence from chloroplasts in magenta. Fluorescence imaging was performed on a Leica SP5 confocal microscope. Shown are maximum projections of Z-stacks. The definition of flower stages is as described previously46. j–k, Confocal images of eGFP fluorescence of proAtSWEET9:AtSWEET11–eGFP fusion showing subcellular localization at plasma membrane and Golgi of lateral nectaries in a mature flower at floral stage 14–15 (open flower); and a close-up image of the subcellular localization of AtSWEET11–eGFP in the nectary cells (k). j, k, Scale bars, 5 μm. l, m, Flowers of wild-type (l) and Atsweet9-1 mutant (m) plants stained with Lugol’s iodine solution 4 h after dawn: starch in the floral stalk of Atsweet9-1. Arrow indicates starch accumulation in the petiole. l, m, Original magnification, ×10.
