Auxin and Strigolactone Signaling Are Required for Modulation of Arabidopsis Shoot Branching by Nitrogen Supply    . Issue 1 (24th July 2014)

• Record Type: Journal Article
• Authors: de Jong, Maaike; George, Gilu; Ongaro, Veronica; Williamson, Lisa; Willetts, Barbara; Ljung, Karin; McCulloch, Hayley; Leyser, Ottoline
• Is Part Of: Plant physiology. Volume 166:Issue 1(2014)
• Page Start: 384
• Page End: 395
• Publication Date: 2014-07-24
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.114.242388
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Limited N supply suppresses shoot branching in Arabidopsis in a process that requires auxin and strigolactone signaling and involves an increase in auxin export from active shoot apices . Abstract: The degree of shoot branching is strongly affected by environmental conditions, such as nutrient availability. Here we demonstrate that nitrate limitation reduces shoot branching in Arabidopsis ( Arabidopsis thaliana ) both by delaying axillary bud activation and by attenuating the basipetal sequence of bud activation that is triggered following floral transition. Ammonium supply has similar effects, suggesting that they are caused by plant nitrogen (N ) status, rather than direct nitrate signaling. We identify increased auxin export from active shoot apices, resulting in increased auxin in the polar auxin transport stream of the main stem, as a likely cause for the suppression of basal branches. Consistent with this idea, in the auxin response mutant axr1 and the strigolactone biosynthesis mutant more axillary growth1, increased retention of basal branches on low N is associated with a failure to increase auxin in the main stem. The complex interactions between the hormones that regulate branching make it difficult to rule out other mechanisms of N action, such as up-regulation of strigolactone synthesis. However, the proposed increase in auxin export from active buds can also explain how reduced shoot branching is achieved without compromising root growth, leading to the characteristic shift in relative biomass allocation to the root when N is limiting.