The OfJAZ gene family in Osmanthus fragrans: IV-OfJAZs regulate petal senescence via hormonal crosstalk

Plant-specific repressors in the jasmonic acid (JA) signaling pathway, jasmonate ZIM-domain (JAZ) proteins are pivotal for growth, development, and stress responses. In Osmanthus fragrans , petal senescence affects ornamental quality and flower longevity, yet the underlying molecular mechanisms remain largely unexplored. Here, 15,045 differentially expressed genes (DEGs) were discovered utilizing RNA-seq of six developmental phases of O. fragrans petals. Weighted gene coexpression network analysis (WGCNA) revealed a coexpression module ETHYLENE INSENSITIVE 3 ( EIN3 )-LIKE ( OfEIL7 )– OfJAZ , which showed strong correlation with JA and ethylene signaling-related genes. Genome-wide analysis identified 23 OfJAZ genes, clustered into four phylogenetic subfamilies. Conservation of TIFY and Jas domains was observed in most OfJAZ proteins, whereas subfamily-specific variations in structural features and motif composition were detected. The OfJAZ family originated under purifying selection and mainly grew by segmental duplication. Haplotype analysis revealed substantial genetic variation among cultivars, with certain IV- and V- OfJAZs exhibiting conserved haplotypes. IV- OfJAZs were enriched in methyl jasmonate (MeJA)-responsive cis -elements and predominantly exhibited low DNA methylation. Expression profiling indicated that several IV- OfJAZs ( OfJAZ3 , OfJAZ7 , OfJAZ15 , and OfJAZ17 ) were upregulated during late petal senescence, with MeJA-induced expression patterns paralleling natural petal senescence, whereas ethylene treatment generally suppressed their expression. The interaction between OfJAZ3 and OfJAZ17 and OfEIL7 may delay leaf senescence under JA-ethylene crosstalk regulation, as shown by transgenic tobacco and O. fragrans , and yeast two-hybrid (Y2H) experiments. The OfJAZ gene family in petal senescence is thoroughly characterized in this work, providing theoretical underpinnings for molecular breeding techniques meant to improve attractive features and prolong floral lifetime. • Weighted gene coexpression analysis identified an EIN3-JAZ hormone related module. • A total of 23 OfJAZ genes were identified at the whole genome-wide level. • Most IV-OfJAZs increased in petal senescence and by MeJA, but repressed by ethylene. • OfJAZ3 and OfJAZ17 interact with OfEIN3 to delay senescence. • This study provides new insights into flowering extension and ornamental improvement.