Functional analysis of sugarcane sucrose
transporter ShSUT1 by expression in oocytes and two-electrode voltage clamping.
Chih-Wei Hsi
The sugarcane (Saccharum hybrid) sucrose transporter ShSUT1 is a monocot transporter which is mainly expressed in stem internode and mature leaves. Many studies of sucrose transporters have been conducted on dicot plants. The sucrose affinity and substrate specificities of SUTs of Arabidopsis have been analyzed in detail. However, the understanding of SUT in monocot plant is very limited. In this paper, ShSUT1 was expressed in the Xenopus oocytes and use two-extrode voltage clamping was used to test the affinity of the sucrose and substrate specificities of physiological and synthetic glucosides. The result showed that sucrose induced inward currents with a K0.5 of 8.74 ± 0.93 mM at pH 5.5 and a membrane potential -137 mV. The other substrates transported by ShSUT1 were maltose, salicin, α-paranitrophenylglucoside and α-phenylglucosides. The result indicated that ShSUT has high affinity of sucrose and is highly selective for α-linked sugars. These results provide an insight into the transport mechanism of ShSUT1 and reveal differences compared with previously analyzed sucrose transporters.