Jasmonic Acid and Salicylic Acid Pretreatment Differentially Modulates Photosynthesis-Related Transcription, Redox Homeostasis, and Defense Gene Expression in Mulberry Against Glyphodes pyloalis
Glyphodes pyloalis Walker is a devastating phytophagous pest of mulberry (Morus spp.) that severely compromises leaf yield and quality, thereby threatening sericultural productivity. Although jasmonic acid (JA) and salicylic acid (SA) are well-established regulators of plant antiherbivore defenses, their specific roles in modulating mulberry responses to G. pyloalis herbivory remain poorly understood. Here, we employed an integrative approach combining herbivory bioassays, exogenous hormone treatment, physiological analysis, and RNA-sequencing (RNA-seq) to dissect JA- and SA-mediated defense networks in mulberry. Exogenous application of both hormones enhanced chlorophyll content, with JA exerting the strongest effect. However, they differentially modulated antioxidant enzyme activities, with SA primarily elevating superoxide dismutase (SOD) and JA enhancing peroxidase (POD) and catalase (CAT). Transcriptomic and functional-enrichment analyses showed that JA-responsive DEGs were predominantly associated with photoprotection, carbohydrate metabolism, phenylpropanoid and flavonoid biosynthesis, MAPK signaling, ABC transporters, and defense-related enzyme functions. By comparison, SA-responsive DEGs were strongly associated with photosynthesis-related gene expression, chloroplast organization, carbon metabolism, glutathione metabolism, and systemic immune-related processes. Notably, several key transcription factors, including MaHDZIP1, MaLBD28, MaGATA5, MaTALE2, MaARF4, MaSBP1 and MaSBP12, were upregulated under both hormone treatments. Collectively, these findings indicate that exogenous JA and SA treatments elicited overlapping yet distinct defense-related responses in mulberry. This work provides an integrated physiological and transcriptomic framework for the future development of hormone-mediated strategies against G. pyloalis in sericulture.