The Mitogen-Activated Protein Kinase GhNTF3 Modulates the Arbuscular Mycorrhizal Symbiosis-Immunity Trade-Off in Cotton by Regulating Salicylic Acid Biosynthesis.

Plant immunity is essential for survival against pathogen invasion. However, enhanced immune activation can restrict arbuscular mycorrhizal (AM) fungal colonization. Therefore, plants must finely balance immunity and symbiosis to optimize fitness, but the key regulators underlying this trade-off remain unclear. Here, we identify a novel mitogen-activated protein kinase, GhNTF3, as a central regulator of the AM symbiosis-immunity balance. Knockdown of GhNTF3 promotes AM symbiosis but decreases Verticillium wilt resistance in cotton. GhNTF3 overexpression suppresses AM symbiosis. GhNTF3 interacts with GhWAK13, a previously characterized wall-associated kinase that is specifically induced by AM symbiosis, at the plasma membrane. Genetic evidence indicates that GhWAK13 functions in association with GhNTF3 during AM symbiosis. GhWAK13 negatively regulates salicylic acid (SA) accumulation, whereas GhNTF3 positively regulates SA accumulation during AM symbiosis. Knockdown of SA biosynthesis genes or the SA receptor gene GhNPR1 significantly enhanced AM fungal colonization, whereas exogenous SA application strongly inhibited symbiosis. Moreover, GhNTF3 interacts with GhJAZ6 in the nucleus to enhance Verticillium wilt resistance, potentially through SA accumulation in cotton. Collectively, our findings identify a molecular module in which the interplay between GhNTF3 and GhWAK13 dynamically balances AM symbiosis and Verticillium wilt resistance through antagonistic regulation of the SA signaling pathway.