Trichoderma virens colonization of maize roots triggers rapid accumulation of 12-oxophytodienoate and two T-ketols in leaves as priming agents of induced systemic resistance

摘要

Two oxylipins 12-OPDA (12-Oxo-10(Z),15(Z)-phytodienoic acid) and an Y-ketol, 9,10-KODA (10-oxo-9-hydroxy-12(Z), 15(Z)-octadecadienoic acid) were recently identified as important long-distance-induced systemic resistance (ISR) signals in Trichoderma Wrens-treated maize. On the other hand, jasmonic acid (JA), long believed to be a major signal of ISR, was not involved, as the JA-deficient mutant, opr7 opr8, retained the capacity for T. Wrens-triggered ISR. In order to further understand the biochemicalbasis for ISR priming in maize leaves, diverse oxylipins and phytohormones in the leaves of wild-type maize or ISR-deficient lox10-3 mutants treated with T. virens were quantified. This analysis revealed that 12-OPDA and two novel Y-ketols, 9,12-KOMA (12-Oxo -9-hydroxy-10(￡)-octadecenoic acid) and 9,12-KODA (12-Oxo-9-hydroxy-10(￡),15(Z)-octadecadienoic acid), accumulated at high levels in ISR-positive plants. In support of the notion that 12-OPDA serves as a priming agent for ISR in addition to beinga xylem-mobile signal, leaf pretreatment with this JA precursor resulted in increased resistance to Colletotrichum graminicola. Furthermore, the injection of 9,12-KODA or 9,12-KOMA in wild-type plants enhanced resistance against C. graminicola infection, suggesting that they play roles in ISR priming.