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Shoot-supplied ammonium targets the root auxin influx carrier AUX1 and inhibits lateral root emergence in Arabidopsis

Publication Type:Journal Article
Year of Publication:2011
Authors:LI, BAOHAI, Li, Q, SU, YANHUA, Chen, H, Xiong, L, MI, GUOHUA, Kronzucker, HJ, SHI, WEIMING
Journal:Plant, Cell & Environment
Volume:34
Issue:6
Date Published:2011
ISBN Number:1365-3040
Keywords:ABA, Ammonium toxicity, auxin transport, Root, shoot-derived signal
Abstract:

Deposition of ammonium (NH4+) from the atmosphere is a substantial environmental problem. While toxicity resulting from root exposure to NH4+ is well studied, little is known about how shoot-supplied ammonium (SSA) affects root growth. In this study, we show that SSA significantly affects lateral root (LR) development. We show that SSA inhibits lateral root primordium (LRP) emergence, but not LRP initiation, resulting in significantly impaired LR number. We show that the inhibition is independent of abscisic acid (ABA) signalling and sucrose uptake in shoots but relates to the auxin response in roots. Expression analyses of an auxin-responsive reporter, DR5:GUS, and direct assays of auxin transport demonstrated that SSA inhibits root acropetal (rootward) auxin transport while not affecting basipetal (shootward) transport or auxin sensitivity of root cells. Mutant analyses indicated that the auxin influx carrier AUX1, but not the auxin efflux carriers PIN-FORMED (PIN)1 or PIN2, is required for this inhibition of LRP emergence and the observed auxin response. We found that AUX1 expression was modulated by SSA in vascular tissues rather than LR cap cells in roots. Taken together, our results suggest that SSA inhibits LRP emergence in Arabidopsis by interfering with AUX1-dependent auxin transport from shoot to root.

URL:http://dx.doi.org/10.1111/j.1365-3040.2011.02295.x
Short Title:Plant, Cell & Environment
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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith