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An OPR3-independent pathway uses 4,5-didehydrojasmonate for jasmonate synthesis

2018; Nature Portfolio; Volume: 14; Issue: 2 Linguagem: Inglês

10.1038/nchembio.2540

1552-4469

Andrea Chini, Isabel Monte, Ángel M. Zamarreño, Mats Hámberg, Steve Lassueur, Philippe Reymond, Sally Weiss, Annick Stintzi, Andreas Schaller, Andrea Porzel, José María García‐Mina, Roberto Solano,

Plant Virus Research Studies

OPR3 is required to reduce the JA-Ile precursor OPDA. Analyses of JA levels in a loss-of-function opr3-3 mutant identified an OPR3-independent pathway for JA-Ile biosynthesis, based on OPDA conversion to 4,5-ddh-JA and reduction to JA by OPR2. Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele. Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the β-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.