Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 26 mars 2009
Amphi 206 (Cœur d’Ecole) à 14h

Analysis of Plant Sucrose Transporter Function and Redundancy

Alicia Sivitz
BPMP – Equipe Transport et Signalisation du Fer

Sucrose transporters (SUTs) are proton/sucrose cotransporters encoded by small gene families in plants. This redundancy can exist for several reasons. However, it is evolutionarily unlikely that SUTs would be maintained as completely redundant proteins. Rather, SUTs are likely to have slightly different functions. In order to determine how SUTs vary biochemically (in terms of kinetics and substrate specificity), SUTs were functionally characterized by expression in oocytes. Electrophysiology was used to examine the affinity of barley SUT1, Arabidopsis SUC9 and Arabidopsis SUC1. HvSUT1 was found to have a moderate affinity for sucrose with a /K/0.5 of 3.8 mM at pH 5.0 and a membrane potential of –157 mV. AtSUC9 was found to be pH independent and ultrahigh affinity for sucrose with a /K/0.5 value of 0.066 ± 0.025 mM. Substrate specificity was also examined for several type I and type II transporters and it was found that type I sucrose transporters have less specificity and transport both a- and b-linked substrates including plant glucosides arbutin, salicin, helicin, maltose, esculin, and fraxin. Type II sucrose transporters may bind some of the b-linked substrates without transporting them as evidenced by the inhibition of HvSUT1-mediated sucrose transport by b-paranitrophenyl glucoside. AtSUC1 and AtSUC9 were shown to be regulated by intragenic sequences, while AtSUC2 was not. AtSUC1, although similar in transport kinetics to other type I sucrose transporters, plays unique roles in pollen germination, lateral root formation, and sucrose-induced anthocyanin production. In sum, the biochemical function of SUTs varies by phylogenetic type, with type I SUTs having high affinities for sucrose and transporting a wide range of substrates, while type II SUTs are more selective and generally have lower affinities. Nevertheless, the type I SUTs AtSUC1 and AtSUC9 were shown to have distinct functions in planta despite their biochemical

Contact : Grégory Vert

Contacts IBIP :
Sabine Zimmermann
Marc Lepetit
Corinne Dasen
Chantal Baracco