Ectopic expression of OsJAZ6, which interacts with OsJAZ1, alters JA signaling and spikelet development in rice

SUMMARY Jasmonates (JAs) are key phytohormones that regulate plant responses and development. JASMONATE‐ZIM DOMAIN (JAZ) proteins safeguard JA signaling by repressing JA‐responsive gene expression in the absence of JA. However, the interaction and cooperative roles of JAZ repressors remain unclear during plant development. Here, we found that OsJAZ6 interacts with OsJAZ1 depending on a single amino acid in the so‐called ZIM domain of OsJAZ6 in rice JA signaling transduction and JA‐regulated rice spikelet development. In vivo protein distribution analysis revealed that the OsJAZ6 content is efficiently regulated during spikelet development, and biochemical and genetic evidence showed that OsJAZ6 is more sensitive to JA‐mediated degradation than OsJAZ1. Through over‐ and mis‐expression experiments, we further showed that the protein stability and levels of OsJAZ6 orchestrate the output of JA signaling during rice spikelet development. A possible mechanism, which outlines how OsJAZ repressors interact and function synergistically in specifying JA signaling output through degradation titration, is also discussed. Significance Statement OsJAZ1 and OsJAZ6 form a heterocomplex to titrate JA signaling during rice spikelet development. Here, the protein stability of OsJAZ6, rather than the transcriptional activity of the gene, controls the OsJAZ1–OsJAZ6 heterocomplex. Our results illustrate neo‐functionalization of JAZs in rice JA signaling resilience.