Maize SUT1 functions in phloem loading

Sucrose Transporter ZmSut1 Expression and Localization Uncover New Insights into Sucrose Phloem Loading

“…As reported previously, homozygous zmsut1 mutant plants were stunted and did not complete their life cycle in comparison with wild-type plants ( Fig. 11; Slewinski et al, 2009Slewinski et al, , 2010. In contrast, zmsut1 mutant plants carrying the gSUT1-YFP transgene flowered, set seed, and completed their life cycle, indicating that the transgene was able to restore ZmSut1 function ( Fig.…”

“…Another intriguing phenotype of zmsut1 mutant plants was the secretion of droplets with high Suc concentrations from the hydathodes (Supplemental Fig. S1; Slewinski et al, 2010). Because no Suc was detectable in the wild-type guttation fluid, this finding indicated that a high level of Suc was present in the apoplasm (which is contiguous with the xylem transpiration stream) of zmsut1 mutants and supported a role for ZmSut1 in phloem loading.…”

“…2F). As a negative control, we analyzed ZmSut1 expression in zmsut1 mutants, which result from a Dissociation transposable element insertion into the 59 untranslated region of the gene that greatly reduces ZmSut1 RNA abundance (Slewinski et al, 2010;Fig. 2G).…”

Tonoplast Sugar Transporters (SbTSTs) putatively control sucrose accumulation in sweet sorghum stems

“…21 SbSUT1 function is likely conserved between grain and sweet sorghum, and based on orthology with the maize (Zea mays) ZmSUT1 gene, it likely functions in sucrose phloem loading in leaves. [34][35][36] SbSWEET13A showed reduced expression in sweet compared with grain sorghum leaves, whereas SbTST1 and SbTST2 were both more highly expressed in sweet sorghum leaves, suggesting that they may function to import sugars into the vacuole for temporary storage during daylight. In stem tissues, none of the SbSUT or SbSWEET13A genes were differentially expressed, suggesting they do not account for the differences in sugar accumulation.…”

Tie-dyed2Encodes a Callose Synthase That Functions in Vein Development and Affects Symplastic Trafficking within the Phloem of Maize Leaves

“…In maize, loss-of-function mutations in the Sut1 gene confer a strong carbohydrate hyperaccumulation phenotype in leaves (Slewinski et al, , 2010. The mutants are severely impeded in loading Suc into the phloem, which results in high concentrations of Suc, Glc, Fru, and starch in leaves and to premature leaf senescence.…”