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AtSUC3 , a gene encoding a new Arabidopsis sucrose transporter, is expressed in cells adjacent to the vascular tissue and in a carpel cell layer
Author(s) -
Meyer Stefan,
Melzer Michael,
Truernit Elisabeth,
Hümmer Carola,
Besenbeck Rainer,
Stadler Ruth,
Sauer Norbert
Publication year - 2000
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2000.00934.x
Subject(s) - arabidopsis , complementary dna , phloem , biology , arabidopsis thaliana , cytoplasm , open reading frame , biochemistry , amino acid , microbiology and biotechnology , gene , peptide sequence , botany , mutant
Summary The cDNA corresponding to the open reading frame T17M13.3 from Arabidopsis chromosome II was isolated and the encoded protein was characterized as a member of a subgroup of higher plant sucrose transporters. The AtSUC3 ( Arabidopsis thaliana sucrose transporter 3) open reading frame encodes a protein with 594 amino acid residues, being 81 and 82 residues longer than the previously described Arabidopsis sucrose carriers AtSUC1 and AtSUC2. About 50 of these additional amino acids are part of an extended cytoplasmic loop separating the N‐terminal from the C‐terminal half of the protein. For functional characterization the AtSUC3 cDNA was expressed in baker's yeast. Substrate specificities, energy dependence and K m values of the recombinant protein were determined. Removal of the enlarged cytoplasmic loop and expression of the truncated cDNA caused no detectable change in the kinetic properties of the protein, suggesting a transport‐independent function for this cytoplasmic domain. Immunolocalization with an AtSUC3‐specific antiserum identified the protein in a cell layer separating the phloem from the mesophyll and in a single, subepidermal cell layer of the carpels that is important for pod dehiscence. These localizations suggest a possible role of AtSUC3 in the funnelling of sucrose from the mesophyll towards the phloem, and possibly in pod shatter.