Strigolactones activate different hormonal pathways for regulation of root development in response to phosphate growth conditions.

BACKGROUND Strigolactones (SLs) - a group of plant hormones and their derivatives - have been found to play a role in the regulation of root development, in addition to their role in suppression of lateral shoot branching: they alter root architecture and affect root-hair elongation, and SL signalling is necessary for the root response to low phosphate (Pi) conditions. These effects of SLs have been shown to be associated with differential activation of the auxin and ethylene signalling pathways. SCOPE The present review highlights recent findings on the activity of SLs as regulators of root development, in particular in response to low Pi stress, and discusses the different hormonal networks putatively acting with SLs in the root's Pi response. CONCLUSIONS SLs are suggested to be key regulators of the adaptive responses to low Pi in the root by modulating the balance between auxin and ethylene signalling. Consequently, they impact different developmental programmes responsible for the changes in root system architecture under differential Pi supply.