Dimerization and endocytosis of the sucrose transporter StSUT1 in mature sieve elements

Abstract

The sucrose transporter StSUT1 from Solanum tuberosum was shown to be regulated post-translationally by redox reagents. Its activity is increased at least 10fold in the presence of oxidizing agents if expressed in yeast. Oxidation has also an effect on plasma membrane targeting and dimerization of the protein. In response to oxidizing agents, StSUT1 is targeted to lipid raft-like microdomains and SUT1 protein is detectable in the detergent resistant membrane fraction of plant plasma membranes. Interestingly, StSUT1 treated with brefeldin A seems to aggregate in endocytic compartments in mature sieve elements. Further analysis of the SUT1 targeting will certainly provide more information about the putative involvement of lipid raft-like microdomains for endocytic events. We provide here additional information about the dimerization and endocytosis of the SUT1 protein. The oligomerization of overexpressed SoSUT1 from Spinacia oleracea in transgenic potato plants was analyzed by two-dimensional gel electrophoresis and endocytosis of the StSUT1 protein was confirmed by immunogold labeling.Addendum to: Krügel U, Veenhoff LM, Langbein J, Wiederhold W, Liesche J, Friedrich T, Grimm B, Martinoia E, Poolman B, Kühn C. Transport and Sorting of the plant sucrose transporter StSUT1 is affected by post-translational modification. Plant Cell 2008; 20:1-17.