Yu H, Karampelias M , Robert S, Peer W, Swarup R, Ye S, Ge L, Cohen J, Murphy A, Friml j, Estelle M.
ROOT UVB SENSITIVE 1/WEAK AUXIN RESPONSE 3 Is Essential for Polar Auxin Transport in Arabidopsis
Plant Physiology April 2013 Published online before print April 2013

Abstract:
The phytohormone auxin regulates virtually every aspect of plant development. To identify new genes involved in auxin activity, a genetic screen was performed for Arabidopsis mutants with altered expression of the auxin responsive reporter DR5rev:GFP. One of the mutants recovered in the screen, designated as weak auxin response 3 (wxr3), exhibits much lower DR5rev:GFP expression when treated with the synthetic auxin, 2,4-D, and displays severe defects in root development. The wxr3 mutant decreases polar auxin transport and results in a disruption of the asymmetric auxin distribution. The level of the auxin transporters, AUX1 and PINs, is dramatically reduced in the wxr3 root tip. Molecular analyses demonstrate that WXR3 is ROOT UV-B SENSITIVE1 (RUS1), a member of the conserved DUF647 protein family found in diverse eukaryotic organisms. Our data suggests that RUS1/WXR3 plays an essential role in the regulation of polar auxin transport by maintaining the proper level of auxin transporters on the plasma membrane.

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