Abstract
Plant root systems show substantial plasticity responses to the available concentrations of nitrogen sources in the soil, for example through changes in root branching and elongation, and by changes in the root to shoot ratio. In legumes, nodule numbers are reduced when external nitrogen availability increases, and this is partially dependent on genes controlling nodule number by a systemic autoregulation mechanism. The Medicago truncatula sunn1 mutant, defective in a receptor‐kinase controlling nodule numbers, displays pleotropic phenotypes in root system architecture and nitrogen responsiveness. Auxin is one of the hormones mediating changes in root architecture, including in response to nitrogen. Measurements of shoot‐to‐root auxin transport in the sunn1 mutant showed that this mutant had elevated auxin transport, which was unresponsive to nitrogen availability, in contrast to the wild‐type. This correlated with the inability of the root system of sunn1 mutants to alter root architecture in response to a change in nitrogen concentrations. In contrast, nodule numbers of sunn1 mutants were still sensitive to inhibition by external nitrate, suggesting that nitrogen inhibition of nodule numbers involves local responses in the root that don't correlate with changes in shoot‐to‐root auxin transport.
Original language | English |
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Title of host publication | The Model Legume Medicago truncatula |
Publisher | Taylor and Francis |
Pages | 811-816 |
Number of pages | 6 |
ISBN (Electronic) | 9781119409144 |
ISBN (Print) | 9781119409151 |
DOIs | |
Publication status | Published - 13 Dec 2019 |