Arabidopsis LOHN1 peptide modulates lateral root spacing under the control of systemic nitrogen-satiety signaling.
In Arabidopsis thaliana, high nitrogen (N) levels are known to induce a systemic signal that represses lateral root (LR) development. However, the molecular mechanisms underlying this response remain poorly understood. In this study, we identified a cysteine-rich secretory peptide, LATERAL ROOT OVERPRODUCTION UNDER HIGH-NITROGEN CONDITIONS 1 (LOHN1), as a key signaling molecule involved in translating an N-sufficient nutritional status into a morphological response that inhibits LR development. High N supply induces LOHN1 expression in phloem companion cells at the root tip region under the control of shoot-derived glutamate and glutamate receptor-like channel (GLR). LOHN1 secretion into the apoplastic space regulates the expression of auxin transporter genes to reduce the frequency of LR priming and LR founder cell formation, thereby suppressing LR branching. Our data provide a molecular basis for how plants respond to high N supply and control root architecture to achieve proper plant growth.