Researchers have discovered the molecular mechanisms underlying the shoot-to-root stage of nitrogen-demand signaling in plants. The team found that genes encoding CEPD polypeptides are switched on in the shoots in response to nitrogen starvation in the roots. These polypeptides then descend into the roots, and activate a nitrate transporter gene only if sufficient nitrate is available in the surrounding soil. These findings have implications for maximizing plant nutrient acquisition and improving agricultural productivity.