Poster: Membrane Transport

Abs # 1212: Expression of Plant Inositol Transporters in Yeast

Presenter:	Miyazaki, Saori , saori@life.uiuc.edu
Authors	Miyazaki, Saori  (A)   Rice, Michael  (B)   Quigley, Francoise  (C)   Bohnert, Hans J.  (A)
Affiliations:	(A): Department of Plant Biology and Crop Sciences, University of Illinois (B): Department of Biochemistry, University of Arizona (C): Université Joseph Fourier, Laboratoire de Genetique Moleculaire des Plantes

ITRs, inositol transporters, are membrane proteins in the hexose transporter super-family. We have characterized plant ITR-like coding regions from Mesembryanthemum crystallinum and Arabidopsis thaliana by their expression in yeast strains deficient in inositol biosynthesis and compromised in inositol uptake. Both At-ITR1 and Mc-ITR1 were capable of complementing the uptake deficiency of the cells albeit at lower efficiency compare to complementation by yeast ITR2. All ITRs used were also capable of taking up a methylated inositol-derivative, D-ononitol. However, Mc-ITR1 was more strongly inhibited in the uptake of D-ononitol in the presence of myo-inositol than yeast ITR, indicating that Mc-ITR1 could have evolved to transport D-ononitol and other methylated inositols that are produced in large quantities in this plant. The ITRs tested were affected in their transport capacity by the proton gradient. At high pH, transport was ineffective, but the addition of sodium at low concentration ameliorated the pH effect. We suggest that the ITRs tested, and possibly the entire plant sub-family, act as sodium /inositol symporters in a proton gradient-dependent fashion. (Supported by NSF, DBI-0223905).