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Abstract Detail


Membrane Transport

Reinders, Anke [1], Sivitz, Alicia B. [1], Ward, John M. [1].

Functional analysis of the type III sucrose transporter LjSUT4 from Lotus japonicus.

Phylogenetic analysis was used to differentiate three types of sucrose transporters in plants: type I, II and III (1). To determine whether these types have different functional properties, we set out to functionally characterize members of each type in detail by expression in Xenopus oocytes and two-electrode voltage clamping. Analyses have been performed for the type I SUTs AtSUC2 and AtSUC9 from Arabidopsis (2, 3) and the type II SUTs HvSUT1 and ShSUT1 from barley and sugarcane respectively (4, 5). Analysis of type III SUTs has been hampered by the fact that the sole type III SUT from Arabidopsis, AtSUT4 and the one from barley, HvSUT2 did not express sufficiently in Xenopus oocytes. Here we are presenting results from the expression of the type III SUT from Lotus japonicus, a sucrose transporter highly expressed in developing nodules (6). LjSUT4 is a proton-coupled sucrose uptake transporter with low apparent affinity for sucrose (K0.5 = 12.9 ± 2.9 mM at pH 5.0). The affinity is pH dependent, with lower apparent affinities at higher pH. The substrate specificity of LjSUT4 is rather broad, similar to the previously characterized type I SUT AtSUC2. These findings are especially interesting in light of recent studies indicating that type III SUTs closely related to LjSUT4 may be localized to the vacuolar membrane (AtSUT4, HvSUT2; 7) or function as uncoupled facilitators (PsSUF4; 8).
(1) Aoki et al. (2003) Plant Cell Physiol 44:223-32
(2) Chandran et al. (2003) J Biol Chem 278:44320-5
(3) Sivitz et al., (2007) Plant Physiol 143:188-98
(4) Sivitz et al. (2005) Plant Cell Physiol 46:1666-73
(5) Reinders et al. (2006) Plant Cell Environ 29:1871-80
(6) Flemetakis et al. (2003) J Exp Bot. 54:1789-9
(7) Endler et al. (2006) Plant Physiol 141:196-207
(8) Zhou et al. (2007) Plant J. 49:750-64


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1 - University of Minnesota, Plant Biology, 250 Biological Sciences Center, 1445 Gortner Ave., St. Paul, MN, 55108, USA

Keywords:
sucrose transport
symport
Lotus
Xenopus
Arabidopsis.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P10010
Abstract ID:1838


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