Guangjie Li Baohai Li Gangqiang Dong Xiaoyu Feng Herbert J. Kronzucker and Weiming Shi. Ammonium-induced shoot ethylene production is associated with the inhibition of lateral root formation inArabidopsis.  J. Exp. Bot. 2013 doi: 10.1093-jxb-ert019

Abstract

Foliar NH₄⁺ exposure is linked to inhibition of lateral root (LR) formation. Here the role of shoot ethylene in NH₄⁺-induced inhibition of LR formation in Arabidopsis was investigated using wild-type and mutant lines that show either blocked ethylene signalling (etr1) or enhanced ethylene synthesis (eto1 xbat32). NH₄⁺ exposure of wild-type Arabidopsis led to pronounced inhibition of LR production chiefly in the distal root and triggered ethylene evolution and enhanced activity of the ethylene reporter EBS:GUS in the shoot. It is shown that shoot contact with NH₄⁺ is necessary to stimulate shoot ethylene evolution. The ethylene antagonists Ag⁺ and aminoethoxyvinylglycine (AVG) mitigated LR inhibition under NH₄⁺ treatment. The decrease in LR production was significantly greater for eto1-1 and xbat32 and significantly less for etr1-3. Enhanced shoot ethylene synthesis-signalling blocked recovery of LR production when auxin was applied in the presence of NH₄⁺ and negatively impacted shoot AUX1 expression. The findings highlight the important role of shoot ethylene evolution in NH₄⁺-mediated inhibition of LR formation.