The Fungal Phytotoxin Lasiojasmonate A Activates the Plant Jasmonic Acid Pathway

Jasmonates are signaling compounds that regulate plant responses to stress. Jasmonic acid (JA) is the direct precursor of the bioactive plant hormone JA-Ile, the ligand of the COI1-JAZ co-receptor complex. JA, its methyl ester and three furanonyl esters were recently isolated from the grapevine pathogen Lasiodiplodia mediterannea sp. The JA ester lasiojasmonate A (LasA) is the first reported naturally occurring JA-furanone, whose mode of action is currently unexplored. Here we show that LasA activates many JA-regulated responses in planta, including protein degradation, gene expression, and physiological processes. These in vivo effects required LasA conversion into JA, formation of JA-Ile and its recognition by the plant JA-Ile perception complex. These data suggest a mode of action of the natural fungal LasA as an inactive JA pool that can be transformed into the bioactive JA-Ile form. We propose that fungal production of JA derivates such as LasA occur at late infection stages to induce plant JA responses such as cell death, and facilitate fungal infection.