The HvSUT1 gene encodes a membrane transport protein which mediates
the energy-dependent transport of saccharose (sucrose) across cell
membranes against a concentration gradient. Sucrose
transporters are thought to be among the basic components of all
higher plants, since saccharose is the universal transport form of
all photoassimilates.
In barley tissue, messenger RNA that encodes the HvSUT protein was
found at the central exchange point between the maternal (parent
plant) and filial (grain) parts of the plant. Induction of the
HvSUT1 gene is associated with an increase in sucrose content in
the developing grain, with the production of enzymes that play a
role in starch formation, and with starch accumulation in the
endosperm during corn formation. The HvSUT1 protein, therefore,
appears to be an important controlling element for the import of
sucrose into the endosperm. The function and mode of action of this
gene has been closely examined in expression studies on baking
yeast. Apart from the transport of sucrose, the gene is not known
to have any additional functions.
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