RT Journal Article
SR Electronic
T1 Macromolecular Trafficking Indicated by Localization and Turnover of Sucrose Transporters in Enucleate Sieve Elements
JF Science
JO Science
FD American Association for the Advancement of Science
SP 1298
OP 1300
DO 10.1126/science.275.5304.1298
VO 275
IS 5304
A1 Kühn, Christina
A1 Franceschi, Vincent R.
A1 Schulz, Alexander
A1 Lemoine, Rémi
A1 Frommer, Wolf B.
YR 1997
UL http://science.sciencemag.org/content/275/5304/1298.abstract
AB The leaf sucrose transporter SUT1 is essential for phloem loading and long-distance transport of assimilates. Both SUT1 messenger RNA (mRNA) and protein were shown to be diurnally regulated and to have high turnover rates. SUT1 protein was detected by immunolocalization in plasma membranes of enucleate sieve elements (SEs) in tobacco, potato, and tomato. Analysis by in situ hybridization showed that SUT1 mRNA localizes mainly to the SE and is preferentially associated with plasmodesmata. Antisense inhibition of SUT1 expression under control of a companion cell (CC)-specific promoter indicated synthesis of SUT1 mRNA in the CC. These results provide evidence for targeting of plant endogenous mRNA and potentially SUT1 protein through phloem plasmodesmata and for sucrose loading at the plasma membrane of SE.