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

Mardi 1er juillet 2014
Amphi 2 (Bât 2 Bis) à 10h

Polar localization and boron-dependent vacuolar trafficking of boric acid/borate transporters in Arabidopsis thaliana

Junpei Takano
Graduate School of Agriculture, Hokkaido University, Japan

Boron (B) is essential for plant growth through its function in cross-linking cell wall pectin. Boron mainly exists as uncharged boric acid in solution, and thus is relatively easily transported across biological membranes. However, in the roots of Arabidopsis thaliana under low B conditions, a boric acid channel NIP5;1 and a boric acid/borate exporter BOR1 are required for efficient B uptake and translocation (Takano et al. 2002 Nature, Takano et al. 2006 Plant Cell). NIP5;1 and BOR1 are located in the plasma membrane (PM) with polarity toward soil- and stele-side, respectively, in various root cells (Takano et al. 2010 PNAS). The opposite polar-localization is considered to be important for directional transport of B.Besides it essentiality, B is toxic when it is accumulated at mM concentrations in tissues. Importantly, upon high B supply, NIP5;1 is down-regulated through degradation of mRNA (Tanaka et al. 2011, Plant Cell), and BOR1 is ubiquitinated and degraded in vacuole via endocytic pathway (Takano et al. 2005 PNAS, Kasai et al. 2011, JBC, Yoshinari et al. 2012). These machineries are apparently important to avoid excessive translocation of B.Our group is currently investigating the mechanisms underlying the polar localization and the vacuolar-trafficking of B transporters. Our forward-genetics approach using GFP-NIP5;1 has to-date identified several mutants defective in normal localization of NIP5;1 and a responsible gene for proper endomembrane organization (Uehara et al. 2014 PCP). Structure-function analyses revealed important amino acids for the polar localization of NIP5;1 and for both the polar localization and the vacuolar trafficking of BOR1. Roles of a dynamin protein and clathrin adaptor proteins in BOR1 trafficking have been investigated. Based on these results, I will discuss the mechanisms for the polar localization and the vacuolar-trafficking of B transporters and their possible application.

Contact : Doan Luu

Contacts IBIP :
Sabine Zimmermann
Alexandre Martinière
Christine Granier
Chantal Baracco