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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.

Floral patterning is regulated by intricate networks of floral identity genes. The peculiar MADS32 subfamily genes, absent in eudicots but prevalent in monocots, control floral organ identity. However, how the MADS32 family genes interact with other floral homeotic genes during flower development is mostly unknown. We show here that the rice homeotic transcription factor OsMADS32 regulates floral patterning by interacting synergistically with E class protein OsMADS6 in a dosage-dependent manner. Furthermore, our results indicate important roles for OsMADS32 in defining stamen, pistil, and ovule development through physical and genetic interactions with OsMADS1, OsMADS58, and OsMADS13, and in specifying floral meristem identity with OsMADS6, OsMADS3, and OsMADS58, respectively. Our findings suggest that OsMADS32 is an important factor for floral meristem identity maintenance and that it integrates the action of other MADS-box homeotic proteins to sustain floral organ specification and development in rice. Given that OsMADS32 is an orphan gene and absent in eudicots, our data substantially expand our understanding of flower development in plants.