Multiple amino acid sequence alignment and transmembrane domain analysis of SUT proteins. a Alignment of amino acid sequences from potato SUT4 (StSUT4; Genbank accession AF237780), tomato SUT4 (LeSUT4; AF176950), Arabidopsis SUT4 (AtSUT4; AY072092), and rice OsSUT2 (HQ875341). TM transmembrane domain. b Comparison of SUT protein structures. The inside and outside membrane regions and transmembrane domains of OsSUT2, StSUT4, AtSUT4, LeSUT4, AtSUT2 (AK226970), and LeSUT2 (AF166498) were predicted using TMMOD software.