Nitrogen signalling pathways shaping root system architecture: an update

• Root architecture is shaped through N interactions with primary and lateral roots.
• Lateral root development is regulated by both systemic and local N signals.
• There are multiple checkpoints in lateral root development subject to N regulation.
• Signalling by nitrate, glutamate and the plant's internal N status are reviewed.
• Interactions with auxin signalling are important to N regulation of root branching.

Root system architecture is a fundamentally important trait for resource acquisition in both ecological and agronomic contexts. Because of the plasticity of root development and the almost infinite complexity of the soil, root system architecture is shaped by environmental factors to a much greater degree than shoot architecture. In attempting to understand how roots sense and respond to environmental cues, the striking effects of nitrate and other forms of nitrogen on root growth and branching have received particular attention. This minireview focuses on the latest advances in our understanding of the diverse nitrogen signalling pathways that are now known to act at multiple stages in the process of lateral root development, as well as on primary root growth.