Integrated Physiological and Transcriptomic Analysis of Early Responses to Mechanical Wounding in Camellia oleifera Leaves Identifies CoWRKY75 as a Candidate Wound-Responsive Transcription Factor

Mechanical wounding is a common physical stress affecting Camellia oleifera during cultivation and harvesting; however, its early physiological and transcriptional responses remain poorly understood. In this study, leaves of C. oleifera ‘Huashuo’ were artificially wounded and collected at different time points. Progressive accumulation of H2O2 and O2− was observed following wounding, as indicated by enhanced DAB and NBT staining. The activities of SOD, CAT, POD, GPX, and APX generally increased, with POD showing the greatest increase. GSH content increased overall, whereas AsA content reached its highest level at 6 h. RNA-seq analysis identified 2520 upregulated and 457 downregulated genes in the 1 h versus 0 h comparison, representing the largest number of differentially expressed genes among the examined time-point comparisons. These genes were mainly enriched in plant–pathogen interaction, MAPK signaling pathway–plant, plant hormone signal transduction, phenylpropanoid biosynthesis, and jasmonic acid biosynthesis and signaling pathways. Among the wound-responsive WRKY genes, CoWRKY75 showed a time-dependent increase in expression and reached its highest level at 6 h. RT-qPCR analysis confirmed a trend consistent with the RNA-seq data. CoWRKY75 encodes a 157-amino-acid protein with a typical WRKY domain, and the protein mainly localizes in the nucleus. Heterologous overexpression of CoWRKY75 in Arabidopsis thaliana resulted in a distinct early-flowering phenotype, suggesting that CoWRKY75 may have a role in plant developmental regulation. These results characterize the early physiological and transcriptional responses of C. oleifera leaves to mechanical wounding and identify CoWRKY75 as a candidate WRKY transcription factor associated with the mechanical wounding response.