期刊
PLANTA
卷 220, 期 6, 页码 817-825出版社
SPRINGER
DOI: 10.1007/s00425-004-1399-y
关键词
Saccharum; sucrose transport; sugarcane; sugar accumulation
A transporter with homology to the SUT/SUC family of plant sucrose transporters was isolated from a sugarcane (Saccharum hybrid) stem cDNA library. The gene, designated ShSUT1, encodes a protein of 517 amino acids, including 12 predicted membrane-spanning domains and a large central cytoplasmic loop. ShSUT1 was demonstrated to be a functional sucrose transporter by expression in yeast. The estimated K-m for sucrose of the ShSUT1 transporter was 2 mM at pH 5.5. ShSUT1 was expressed predominantly in mature leaves of sugarcane that were exporting sucrose and in stem internodes that were actively accumulating sucrose. Immunolocalization with a ShSUT1-specific antiserum identified the protein in cells at the periphery of the vascular bundles in the stem. These cells became lignified and suberized as stem development proceeded, forming a barrier to apoplasmic solute movement. However, the movement of the tracer dye, carboxyfluorescein from phloem to storage parenchyma cells suggested that symplasmic connections are present. ShSUT1 may have a role in partitioning of sucrose between the vascular tissue and sites of storage in the parenchyma cells of sugarcane stein internodes.
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