Journal Article

Transport Activity of Rice Sucrose Transporters OsSUT1 and OsSUT5

Ye Sun, Anke Reinders, Kathryn R. LaFleur, Toko Mori and John M. Ward

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 1, pages 114-122
Published in print January 2010 | ISSN: 0032-0781
Published online December 2009 | e-ISSN: 1471-9053 | DOI:

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  • Biochemistry
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  • Plant Sciences and Forestry


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Expression in Xenopus oocytes and electrophysiology was used to test for transport activity of the five sucrose transporter (SUT) homologs from rice. Expression of OsSUT1 and OsSUT5 resulted in sucrose-dependent currents that were analyzed by two-electrode voltage clamping. We examined the transport kinetics, substrate specificity and pH dependence of sucrose transport and K0.5 for sucrose. OsSUT1 showed similar features to those of other type II SUTs from monocots examined previously, with a K0.5 value of 7.50 mM at pH 5.6. In contrast, OsSUT5 had a higher substrate affinity (K0.5 = 2.32 mM at pH 5.6), less substrate specificity and less pH dependence compared with all type II SUTs tested to date. Regulation of the rice SUTs, as well as ZmSUT1 from maize and HvSUT1 from barley, by reduced (GSH) and oxidized (GSSG) forms of glutathione was tested. GSSG and GSH were found to have no significant effect on the activity of sucrose transporters when expressed in Xenopus oocytes. In conclusion, differences in transport activity between OsSUT1 and OsSUT5 indicate that type II SUTs have a range of transport activities that are tuned to their function in the plant.

Keywords: Electrophysiology; Oryza sativa; OsSUT1; OsSUT5; Rice; Sucrose transporter

Journal Article.  4950 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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