Methyl jasmonate enhances rice tolerance to alkaline stress via the auxin pathway

• Alkaline stress significantly increased methyl jasmonate (MeJA) in rice seedlings. • Jasmonate-responsive genes were consistently activated by alkaline stress. • MeJA enhanced rice tolerance to alkaline stress through the auxin pathway. Soil alkalization is a major challenge for global crop production. This study reveals a novel defense mechanism in rice seedlings against alkaline stress, involving methyl jasmonate (MeJA) and auxin pathways. Under alkaline stress (15 mM Na 2 CO 3 ), rice seedlings exhibited elevated levels of endogenous MeJA and upregulation of JA-responsive genes. Pre-treatment with MeJA (50 µM) significantly improved seedling survival, growth, and mitigated root damage under alkaline stress. This treatment also upregulated genes associated with cell death suppression ( OsBI1 ) and stress tolerance ( OsJRL, OsNAC ). Notably, MeJA pre-treatment increased auxin (indole-3-acetic acid, IAA) levels in roots, and upregulated genes involved in IAA synthesis ( OASA1, OASA2 ) and auxin signaling ( Aux/IAA, ARFs ). Blocking auxin transport with N-1-naphthylphthalamic acid intensified root damage under alkaline stress and diminished the protective effect of MeJA. These results highlight the crucial role of MeJA-induced activation of auxin pathway in enhancing rice tolerance to alkaline stress, and provide valuable insights for developing strategies to improve crop resilience in alkaline soils.