A Root‐Leaf‐Root Signalling Loop Mediates Tomato Defence Specifically Against Meloidogyne incognita

Root‐knot nematodes (RKNs) are among the most devastating biotic threats to global agriculture, causing annual crop losses estimated between $100 and $160 billion worldwide. Far from being passive victims, plants mount sophisticated systemic defence responses that integrate environmental cues with internal hormonal and electrical signals. This review explores the progression of research from the understanding of shoot‐to‐root jasmonic acid (JA) flux as a systemic immune signal against nematodes to the recent discovery of a complete “root‐to‐leaf‐to‐root” signalling loop in tomato. Within this loop, the mobile transcription factor ELONGATED HYPOCOTYL 5 (HY5) integrates light perception, glutamate receptor‐like (GLR3.5)‐mediated electrical signalling, and calcium‐calmodulin cascades to orchestrate a sustained jasmonic acid burst. This review critically assesses the remarkable complexity of JA signalling in nematode defence, discusses whether the inter‐organ communication loop is conserved beyond tomato, and asks whether analogous mechanisms operate against other root pathogens. By raising open questions and highlighting parallels from related fields, we aim to stimulate research that moves this discovery from a model‐plant phenomenon to a broadly applicable framework for engineering durable nematode resistance.