Flower jasmonates control fertility but are largely disconnected from defense metabolites in reproductive tissues of rice

Although the sterile phenotypes of Osjar1 and Osaoc (hebiba) mutants corroborate the essential role of jasmonates (JAs) in the reproductive development of rice (Oryza sativa L.), it remains unclear how other JA-dependent defense functions operate in reproductive tissues. We showed that various JAs, including bioactive jasmonoyl-l-isoleucine (JA-Ile), gradually accumulate in rice spikelets, and peak at anthesis, but the majority of JAs remain localized in the stamens. Whereas other spikelet parts contained only a low basal level of JAs, whole flowers responded to mechanical damage by the elicitation of a strong JA burst. Similarly, whole flowers showed increases in concentrations of the defense metabolites phenolamides and momilactone diterpenes (which were already present at basal concentrations) in response to wounding, but these contents were only partially dependent on JA. Our data suggest that whereas JAs acquired essential roles in rice fertility, floral defense was largely diverted to one or more other signaling pathways that complement the canonical JA and/or JA-Ile stress signaling in the reproductive parts of rice.