title: Auxin and strigolactone signaling are required for modulation of Arabidopsis shoot branching by nitrogen supply.
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.
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Maaike
authors: M
authors: de Jong
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Gilu
authors: G
authors: George
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Veronica
authors: V
authors: Ongaro
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Lisa
authors: L
authors: Williamson
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Barbara
authors: B
authors: Willetts
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Karin
authors: K
authors: Ljung
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.).
authors: Hayley
authors: H
authors: McCulloch
authors: Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom (M.d.J., H.M., O.L.);Department of Biology, University of York, York YO10 5DD, United Kingdom (G.G., V.O., L.W., B.W., O.L.); andUmeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden (K.L.) ol235@cam.ac.uk.
authors: Ottoline
authors: O
authors: Leyser
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007783:Lactones / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development*
chemical_list: D007210:Indoleacetic Acids; D007783:Lactones; D009566:Nitrates; D009584:Nitrogen