Referenced in: none

Automatically associated channels: Slo1

Title: Polar localization and degradation of Arabidopsis boron transporters through distinct trafficking pathways.

Authors: Junpei Takano, Mayuki Tanaka, Atsushi Toyoda, Kyoko Miwa, Koji Kasai, Kentaro Fuji, Hitoshi Onouchi, Satoshi Naito, Toru Fujiwara

Journal, date & volume: Proc. Natl. Acad. Sci. U.S.A., 2010 Mar 16 , 107, 5220-5

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/20194745

Abstract
Boron (B) is essential for plant growth but is toxic when present in excess. In the roots of Arabidopsis thaliana under B limitation, a boric acid channel, NIP5;1, and a boric acid/borate exporter, BOR1, are required for efficient B uptake and subsequent translocation into the xylem, respectively. However, under high-B conditions, BOR1 activity is repressed through endocytic degradation, presumably to avoid B toxicity. In this study, we investigated the localization of GFP-tagged NIP5;1 and BOR1 expressed under the control of their native promoters. Under B limitation, GFP-NIP5;1 and BOR1-GFP localized preferentially in outer (distal) and inner (proximal) plasma membrane domains, respectively, of various root cells. The polar localization of the boric acid channel and boric acid/borate exporter indicates the radial transport route of B toward the stele. Furthermore, mutational analysis revealed a requirement of tyrosine residues, in a probable cytoplasmic loop region of BOR1, for polar localization in various cells of the meristem and elongation zone. The same tyrosine residues were also required for vacuolar targeting upon high B supply. The present study of BOR1 and NIP5;1 demonstrates the importance of selective endocytic trafficking in polar localization and degradation of plant nutrient transporters for radial transport and homeostasis of plant mineral nutrients.