Magnesium oxide induces immunity against Fusarium wilt by triggering the jasmonic acid signaling pathway in tomato.

• MgO could enhance Fusarium oxysporum f. sp. lycopersici (FOL) host resistance. • MgO-pretreatment of tomato induced long-term immunity against FOL. • Activation of jasmonic acid signaling is essential for MgO-induced FOL immunity. • A primed state for defense is established in MgO-pretreated tomato plants. • MgO may induce immunity against a wide range of pathogens. Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici (FOL), is a worldwide tomato disease. Although Fusarium wilt management remains unsuccessful, enhancing host FOL resistance using magnesium oxide to activate plant immunity may enable effective control. We demonstrated that MgO-pretreatment of roots induced FOL resistance in susceptible tomato plants. Resistance was not induced in tomato mutants deficient in the jasmonic acid (JA) signaling pathway, whereas the opposite trend was observed in mutants deficient in the salicylic acid and ethylene signaling pathways, suggesting that JA signaling activation is essential for MgO-induced FOL immunity. Quantitative real-time polymerase chain reaction analysis of MgO-pretreated tomato plants, and challenge-inoculated with FOL, revealed that MYELOCYTOMATOSIS ONCOGENE HOMOLOG 2 (MYC2), the master regulator of JA signaling, as well as MYC2 -targeted transcription factors that directly regulate the JA-induced transcription of late defense genes and their downstream wound-responsive genes were preferentially upregulated in both roots and stems. Moreover, in MgO-pretreated tomato plants challenge-inoculated with FOL, the late wound-responsive THREONINE DEAMINASE 2 (TD) gene was expressed earlier than its upstream genes, including MYC2 , suggesting that a primed state for defense was established in MgO-pretreated plants. We conclude that MgO is a promising agent for the control of Fusarium wilt. [ABSTRACT FROM AUTHOR]