Genome-Wide Analysis of WRKY Family Reveals Candidate Regulators of Endophyte Mediated Dendrobine Biosynthesis in Dendrobium nobile.

WRKY transcription factors (TFs) are important regulators of plant growth, stress responses, and secondary metabolism; however, their roles in endophyte-mediated dendrobine biosynthesis remain largely unknown in Dendrobium nobile. Here, we identified 63 DnWRKY genes in the D. nobile genome and systematically investigated their potential involvement in endophyte-mediated dendrobine accumulation. Phylogenetic analysis revealed high conservation of DnWRKY proteins within subfamilies. Endophytic fungal co-culture significantly promoted dendrobine accumulation, reaching 0.39 mg g-1 at 14 days, which was 2.6-fold higher than that of the control. Transcriptome and qRT-PCR analyses showed that several DnWRKY genes responded to fungal treatment and exhibited expression patterns consistent with dendrobine accumulation. Among them, DnWRKY18 and DnWRKY4 were significantly positively correlated with key enzyme genes involved in dendrobine biosynthesis, including HMGS, TPS1, and TPS2. Promoter analysis further identified typical W-box elements in these target genes, supporting the possibility of WRKY-mediated transcriptional regulation. These results provide the first evidence linking WRKY TFs to endophyte-induced dendrobine biosynthesis in D. nobile and suggest that DnWRKY18 and DnWRKY4 may serve as candidate positive regulators in this process, establishing a putative regulatory framework for further functional verification of WRKY-mediated dendrobine biosynthesis.